Glass, Ceramics and Stone
Master’s Thesis
Investigations into Black Spots on Egyptian Limestone Bowls from
the Rijksmuseum van Oudheden, Netherlands
Raven Todd DaSilva 11686731 University of Amsterdam, Amsterdam Supervisor: Kate van Lookeren Campagne (University of Amsterdam) Second Reader: Tamar Davidowitz June 2019
Table of Contents
ABSTRACT ... 4 ENGLISH ... 4 DUTCH ... 6 INTRODUCTION ... 8 1. OBJECTS UNDER STUDY ... 91.1. OBJECT DESCRIPTION AND GENERAL CONDITION ... 9
1.2. EXCAVATION AND HISTORY ... 12 1.2.1 Excavations at Abu Roash ... 12 1.2.2 Abu Roash finds at the Rijksmuseum van Oudheden ... 13 1.2.3. Investigation on formation and appearance ... 14 ... 14 1.3. DESCRIPTION OF PHENOMENA ... 18 1.3.1 Typology of spots ... 18 1.3.2. Spot Mapping ... 25 1.3.3 Tomb Mapping ... 27 2. THE STATE OF THE ART: EGYPTIAN BOWLS AND SPOTS ... 32 2.1. EGYPTIAN LIMESTONE BOWLS ... 32 2.1.1. Extent of production ... 32 2.2. LIMESTONE ... 32 2.2.1. Provenience, quarrying ... 32 2.2.2. Production technique ... 35
2.3. POSSIBLE SOURCES OF THE SPOTS ... 37
2.3.1. Biological Growth on Stone ... 37 2.3.1.1 Fungi ... 38 2.3.1.2. Lichen ... 39 2.3.1.3. Cyanobacteria ... 40 2.3.2. Manganese Dendrites ... 41 2.3.2.1 Composition ... 42 2.3.2.2 Formation ... 45 2.3.2.3 Implications to Stone Substrates ... 46
2.4. SIMILAR BLACK SPOTS AND LIMESTONE BOWLS IN OTHER MUSEUM COLLECTIONS ... 47
2.4.6. Discussion and Conclusion ... 51 3. EXPERIMENTAL ... 52 3.1. INTRODUCTION ... 52 3.2. METHODOLOGY ... 52 Microscopic Investigation ... 52 3.2.1. Hirox 3D Digital Microscopy ... 52 3.2.2. Ultraviolet Light Analysis ... 53 Instrumental Analysis ... 53 3.2.3. X-Ray Fluorescence (XRF) ... 53 3.2.4. X-Ray Diffraction (XRD) ... 53 3.2.5. XRD Sampling ... 54 3.2.6. Scanning Electron Microscopy/ Energy Dispersive X-ray (SEM- EDX) ... 54 3.2.7. SEM-EDX Sampling ... 54 3.3.3. Microscopical Analysis ... 58 3.3.4. XRF ... 58
3.3.5. XRD ... 62
3.3.6. SEM-EDX ... 63
4. CONCLUSION ... 64
5. MANGANESE DENDRITES ON CULTURAL HERITAGE OBJECTS ... 65
5.1. IMPLICATION ON ARCHAEOLOGICAL ARTEFACTS ... 65
5.2. DIFFERENTIATION BETWEEN BIOLOGICAL GROWTH AND MANGANESE DENDRITES ON STONE. 65 ACKNOWLEDGEMENTS ... 67 BIBLIOGRAPHY ... 68 TABLE OF FIGURES ... 79 TABLE OF TABLES ... 82 APPENDIX I: SIMILAR BLACK SPOTS IN OTHER MUSEUM COLLECTIONS ... 83 APPENDIX II: RMO ARCHIVES ... 100 APPENDIX III: RMO SURVEY SELECTION PHOTOS ... 102 APPENDIX IV: RMO SURVEY SELECTION TYPOLOGY ... 111 APPENDIX V: SPOT TYPOLOGY ... 116 APPENDIX VI: SPOT MAPPING ... 124 APPENDIX VII: TOMB MAPPING ... 130 APPENDIX VIII: UV PHOTOGRAPHY ... 135 APPENDIX IX: HIROX 3D MICROSCOPY ... 137 APPENDIX X: XRF RESULTS ... 139 APPENDIX XI: XRD AND SEM SAMPLING ... 150 APPENDIX XII- XRD RESULTS ... 151 APPENDIX XIII: SEM-EDX IMAGES AND RESULTS ... 152 All photos, images and illustrations by Raven Todd DaSilva unless otherwise stated.
Abstract
English The research presented in this thesis, written for the Master of Arts Conservation and Restoration of Cultural Heritage program at the University of Amsterdam in the academic year of 2018/2019, investigates the curious black spots, which are present on multiple limestone objects dating from the Early Dynastic Period in Ancient Egypt, in the collection of the Rijksmuseum van Oudheden (RMO), which were excavated at the site of Abu Roash by the museum in the late 1950s. For the purposes of this research, four limestone bowls from this collection were selected as a case study to investigate the composition of the black spots, and to determine if they pose a risk to the conservation of these objects or to others. The black spots had been on the objects for a long time and there was concern about biological contamination. The bowls were first analysed visually, using various methods of investigation including ultraviolet fluorescence (UV), and microscopy using a Hirox 3D digital microscope. The analysis provided information about the morphology and growth patterns of the spots, which suggested they were of inorganic origin. Further analysis comparing the Abu Roash objects to objects housed in other cultural heritage institutions has shown that this phenomenon is prevalent across many institutions, with none of the museums investigated either not knowing what they were, or deciding not to acknowledge them. The spots on the four bowls, and those on a larger survey selection of other objects from the RMO, were visually examined to create a spot typology based on their shape and then mapped on the case study objects to determine if there were any growth patterns evident. The objects, including the survey selection, were then researched with relation to the tombs from which they had been excavated. This suggested that the tomb’s proximity to water had an effect on the coverage of black spots on the objects. Dr. James A. Harrell suggested the possibility of the spots being mineral deposits, specifically manganese dendrites. These deposits are the result of precipitation from a supersaturated solution. Further investigation was conducted to determine if this was in fact the case. X-ray fluorescence (XRF) analysis proved the presence of manganese as a major element of the black spot composition. X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) were also conducted in an attempt to further define the crystalline nature of the dendrites specific to the bowls from the Abu Roash collection. The fine crystalline form and the 2-dimensionality of manganese dendrites made this analysis difficult. Further analysis such as Fourier Transform Infrared Spectroscopy (FTIR) is required to aid in a more specific identification. Due to the difficulties of analysis, manganese dendrite formation and their exact crystalline composition are not yet completely understood. While further research into manganese dendrites is still needed, the research presented in this thesis provides information regardingthe identification of these mineral deposits and the importance of differentiating these from biological growth when conserving cultural heritage artefacts.
Dutch Dit onderzoek gaat over merkwaardige zwarte vlekken, die voorkomen op een collectie van kalkstenen objecten uit de Vroeg-dynastieke Periode in het oude Egypte. De objecten behoren tot de collectie van het Rijksmuseum van Oudheden (RMO) en zijn opgegraven door het museum op de site Abu Roash aan het eind van de jaren vijftig en ten behoeve van onderzoek zijn vier kalkstenen kommen uit deze collectie geselecteerd als een casus om de samenstelling van deze zwarte vlekken te onderzoeken en om vast te stellen of ze een risico vormen voor de conservering van deze of andere objecten in de collectie. De zwarte vlekken waren al aanwezig ten tijde van hun aanwinst en, vanwege hun uitelijk, waren er zorgen over biologische besmetting. De kommen zijn eerst visueel geanalyseerd met behulp van verschillende onderzoeksmethoden, waaronder ultraviolet light (UV) en microscopie, met gebruik van de Hirox 3D digitale microscoop. Deze analyse heeft inzicht geboden in de morfologie van de vlekken, alsmede een beter begrip omtrent hun vorm en groeipatronen. Verdere analyse die de Abu Roash objecten vergelijkt met objecten uit collecties van andere culturele erfgoed instituties heeft aangetoond dat dit fenomeen wijdverspreid is over vele collecties, desondanks is er geen onderzoek gedaan naar hun samenstelling, oorsprong of risico dat zij meedragen. De vlekken op de vier kommen, en die van een grotere selectie van andere objecten van het RMO, zijn visueel geanalyseerd om een vlektypologie te creëren gebaseerd op hun vorm, die vervolgens in kaart gebracht is op de casus objecten om vast te stellen of er duidelijke groeipatronen aanwezig waren. De objecten, inclusief de surveyselectie, zijn vervolgens gelinkt aan de graven waaruit ze zijn opgegraven. Dit gaf aan dat de nabijheid van water bij het graf een effect heeft gehad op de dekking van de zwarte vlekken op de objecten. Dr. James A. Harrell heeft gesuggereerd dat de vlekken minerale deposities zijn, zogeheten mangaan dendrieten. Deze deposities zijn het gevolg van de neerslag van een oververzadigde oplossing. Verder onderzoek is uitgevoerd om vast te stellen of dit daadwerkelijk het geval was. X-ray fluorescence (XRF) analyse heeft de aanwezigheid van grote hoeveelheden mangaan in de samenstelling van de zwarte vlekken aangetoond. X-ray diffraction (XRD) en scanning electron microscopy met energy dispersive X-ray spectroscopy (SEM-EDX) zijn uitgevoerd in een poging om de kristallijne aard van de dendrieten, die specifiek is voor de kommen van de Abu Roash collectie, verder te definiëren. De fijne kristallijne vorm van de tweedimensionaliteit van de mangaan dendrieten heeft de analyse moeilijk gemaakt, en verdere analyse zoals Fourier Transform Infrared Spectroscopy (FTIR) is nodig om te helpen bij het maken van een specifiekere identificatie. Vanwege de moeilijkheden met de analyse, zijn de samenstelling van de mangaan dendrieten en hun exacte kristallijne compositie nog niet geheel begrepen. Hoewel verder onderzoek naar mangaan dendrieten nodig is, heeft de analyse die gepresenteerd is in deze scriptie informatie verschaft aangaande de identificatie van deze minerale
deposities en het belang dat biologische groei hiervan wordt onderscheiden bij het maken van een conserveringsplan voor culturele erfgoedstukken waarin dit fenomeen aanwezig is.
Introduction
Four limestone bowls dating from the Early Dynastic Period in Egypt from the collection of the Rijksmuseum van Oudheden (objects F.1961/1.163, F.1960/1.188, F.1960/11.196 and F.1960/11.21) were investigated to gain a better understanding of the curious black spots that are visible on the stone surface. These four objects belong to a larger collection of objects that were excavated over the course of three dig seasons at the site of Abu Roash, Egypt during a field project led by Adolf Klasens, then curator of the Egyptian Antiquities department and later director of the museum in the late 1950s. The excavations uncovered multiple cemeteries and hundreds of graves, which housed grave goods and funerary equipment. Renske Dooijes, Conservator at the Rijksmuseum van Oudheden (RMO), first identified this spot phenomenon as an area for further study and presented it as a research topic to the University of Amsterdam as a thesis subject for the Master’s program in Conservation and Restoration of Cultural Heritage. Vessels made of carved stone were extremely common grave goods in the Early Dynastic Period and were fabricated in an extensive range of shapes, sizes and materials. As only the products of finer craftsmanship were buried with the dead, these archaeological finds provide an insight into the most advanced technology of this time.1 The bowls that are the focus of this case study therefore hold important information in regards to the archaeological record of the early dynasties of Ancient Egypt. The artefacts have been housed in the Rijksmuseum van Oudheden since their arrival in the Netherlands after the excavations. Many of the objects have been previously restored, including two of the four selected for this case study (objects F.1961/1.163 and F.1960/1.188). However, there is no conservation documentation from these previous interventions.2 3 The spots vary in shape, size, colour and frequency, and some appear as if they are spreading outwards, with the spots forming starburst or snowflake forms. These star-like forms suggest that they once were, or are currently, in a state of expansion and growth. The composition of the spots and their method of deposition were unknown and it was unclear whether the spots would have an effect on the conservation of the stone underneath. A large concern with the spots was if they are biological in nature. Biological contamination on objects in a collections depot may be a result of environmental conditions of the storage space, or they could have also germinated on the bowls before arriving at the museum. Certain biological contamination has the ability to spread to other1 Jeffrey A. Spencer, Early Egypt: The Rise of Civilization in the Nile Valley. (Norman: University of Oklahoma Press, 1995): 85.
2 Personal communication, Alejandra Mamonde (RMO), 21 February, 2019.
3 For the purposes of this research project, the previous restoration measures will not be investigated or discussed, as they do not pertain to the identification of the black spots.
susceptible objects and cause further damage to a collection if not properly treated and contained. There were no standing records of these bowls in the museum database. Therefore, literature, archival documents and photographs from the three excavation seasons were analysed and experts in the various fields of archaeology, microbiology and geology consulted in order to help identify the history and source of the black spots. In addition, various methods of optical and scientific analysis were applied in order to gain a better understanding of the character, morphology and composition of the spots and to determine their effect (if any) on the limestone surface. The main research question for the investigation into these bowls was: “What is the source of the black spots observed on the Rijksmuseum for Oudheden collection of Egyptian limestone bowls from the Archaic Period and are they damaging to the objects?”
1. Objects Under Study
The four bowls are from a larger collection of finds excavated from the site of Abu Roash led by the Rijksmuseum van Oudheden (RMO) in Leiden, the Netherlands from 1957-1959 and directed by Adolf Klassens. They are of varying shapes and sizes ranging, but all of a generic bowl/basin typology. The archives at the RMO were also searched in order to discover if the spots were mentioned in any of the documentation, or visible in any of the excavation photography. 1.1. Object Description and General Condition The measurement and condition of each bowl is as follows:F.1961/1.163 (Bowl 1) 25cm wide x 11cm high. The stone is a light-coloured limestone and was previously broken into three pieces and restored after excavation. An old restoration fill of an as yet unknown material completed the bowl and has been retouched to mimic the spots on the stone. The bowl has a medium coverage of spots, with many areas not presenting spots. (Figures 1.1, 1.2). F.1960/1.188 (Bowl 2) 21cm wide x 6.7cm high. Light coloured limestone and was previously broken into four pieces and restored upon excavation. The number “888” is inscribed in ink on the inner surface of the bowl. The interior of the bowl is almost completely covered with spots, save for a u-shaped area, continuing from the rim into the centre of the bowl. The verso of the
Figure 1.1 – F.1961/1.163 recto. Figure 1.2 – F.1961/1.163 verso.
bowl presents evidence of an orange paint, slip layer, or layer of stone which has been eroded off in many areas. There is heavy spotting on only one side of the verso, closer to the rim. (Figures 1.3, 1.4). F.1960/11.196 (Bowl 3) 11.5cm wide x 7.5 cm high. Light coloured limestone slipped or painted with a pink/reddish pigment. The bowl is in one piece and does not show signs of previous intervention. The bowl has medium/high coverage of spots, with some areas clear of contamination. There are many brown smudges of various shapes and sizes on this bowl as well. Pigmented area has been broken off or is wearing off in some areas. There is a pencil marking of “AR 45” on the outer rim of the bowl. (Figures 1.5, 1.6).
Figure 1.5 – F.1960/11.196 recto. Figure 1.6 – F.1960/11.196 verso.
F.1960/11.221 (Bowl 4) 25.7cm wide x 8.5cm high. It is a shallow, wide dish with a 9 cm diameter hole in the bottom. The hole was drilled out purposely, and fits a smaller stone disk inside, which has since broken since previous intervention. The main piece is comprised of two previously restored pieces and is whole, apart from a 7.8cm long missing piece in the rim. This small disk is now in 6 pieces ranging in size of 8cm-1cm in length. Spots can be found heavily on both sides of the piece, with most appearing on the larger section, whereas there are very few spots on the disk. There is a pencil marking of “AR 19” on the outer rim of the bowl. (Figures 1.7, 1.8, 1.9) 1.2. Excavation and history 1.2.1 Excavations at Abu Roash The village of Abu Roash4 is located on the edge of the Western Desert, 9km north of the Pyramids of Giza, and 16km west of Cairo (Figure 1.14). 5 The cemeteries date from the Archaic Period, also known as the Early Dynastic Period (c. 3100- 2686 BCE).6 The sites here are a part of a long series of cemeteries from this period, which have been found on both sides of the Nile across Egypt.7 Abu Roash is a wide archaeological area located north of Giza on the west side of the Nile. It is most notably known as the location of the destroyed pyramid of Djedefre, the third pharaoh of the 4th Dynasty and the son of Khufu (Cheops) who is best known for his construction of the Great Pyramid in Giza. Abu Roash is also the most northern site 4 Also known as Abu Rawash, Abu Roach and Abu Roasj.
5 A. Klasens, The Excavations of the Leiden Museum of Antiquities at Abu-Roash. (Leiden: Rijksmuseum Van Oudheden, 1962): 58.
6 For a chronology of Egyptian dynasties, see Figure 1.13. 7 Klasens Abu Roash, 59.
of the Memphite necropoleis and contains an archaeological record dating from the Early Dynastic Period to the Coptic Period. The area excavated by the Dutch team took place in the lower plain of the site, which is now mostly destroyed due to levelling of the plain to make space for modern land reclamation and development.8 Excavations first began at the site of Abu Roash in 1900 by the French Institute of Oriental Archaeology under the direction of Émile Chassinat. Work was later carried out by Pierre Montet in the 1930s and 40s, and more recently in the early 2000s under Y. Tristant.9 None of the stone vessels and fragments were reported to show the same phenomena as those excavated by the Dutch team.10 Therefore, the finds of the French excavations will not be discussed in this research. During the three seasons of the Dutch expedition, three separate cemeteries were investigated (Figure 1.15).11 Hundreds of tombs were found, with 81 having been fully excavated (Figure 1.16). The earliest of the tombs are mud-brick mastaba
tombs of 1st Dynasty nobles,12 but all were found in fairly good condition, although
the larger ones had been plundered. The cemetery is located in the lowest part of the plain, meaning the soil was damp from water infiltration. Because of this, there are only traces left of the wooden coffins, original roofing, reed matting, and basketry.13 Overall, the cemeteries cover the whole of the Archaic Period, which comprise of Dynasties 0-2.14 1.2.2 Abu Roash finds at the Rijksmuseum van Oudheden No records have been located related to the arrival of the Abu Roash finds to the RMO, nor are there reports for the previous restorations.15 The bowls are currently located in the RMO storage facility, on wooden shelves and enclosed with glass doors. The bowls have never been on display. Given this information, the bowls have only been subjected to the museum’s climate since their arrival in the Netherlands.
8 Michel Baud. "Abu Rawash (Abu Roash)." The Encyclopedia of Ancient History, (2012): 1. doi:10.1002/9781444338386.wbeah15009.
9“Inventaire Des Archives Manuscrites.” 2018. IFAO. IFAO: Institut français d'archéologie orientale au Caire. accessed May 10, 2018, http://www.ifao.egnet.net/bases/archives/ms/?cote=Abou Roach. 10 Personal communication, Y. Tristant, Associate Professor of Archaeology, MacQuaire University, Australia, 20 March, 2019.
11 Cemeteries 300, 400 and 800 were excavated successively from 1957-1959. Season one and two consisted solely of cemetery 300 and 400 respectively, whereas season three saw the continuation of work in 400, as well as the excavation of 800. Klasens, Abu Roash.
12 Uphill, E. P. "Abu Rawash." Oxford Art Online, (2003). doi:10.1093/gao/9781884446054.article.t000280.
13 Klasens, Abu Roash, 64. 14 Klasens, Abu Roash, 70.
1.2.3. Investigation on formation and appearance Abu Roash Archives In order to gain a fuller understanding of the history of the bowls, and to see if the spot phenomena were present at the time of their finding, the Abu Roash excavation documents held in the RMO Archives were consulted. From photos taken shortly after fieldwork was completed, it is evident that the spots were already on the bowls from the time of excavation. In a visual comparison using these photos, and the bowls at the museum, it appears that the spots have not grown in size since their arrival in the Netherlands. In regards to notations of the black spots, only two references were found citing the phenomena. In the Catalogue of Objects from the 1958 season, there are two entries for a “cream-coloured, black spotted limestone bowl”.16 No photos are attached to these entries. The bowls with this description originate from tombs 343 and 365, have similar shapes, and were logged seven days apart from each other.17 The bowl from tomb 365 is described as having been restored and a loose bottom, which has been damaged (Figure 1.12). A photo was found in the archives matching this description (Figure 1.10). Given this information, it is possible that the bowl being described is similar to Bowl 4 in this case study (Figure 1.11). 18 16 RMO Archives: Opgravingen, Aboe Roasj, 1958, Box 3 8.2.2/2j- 3e, folder 8.2.2/3a, pp. 4, 5. 17 The bowl found in tomb 343 was entered in the record on 08.02.1958, whereas the bowl found in tomb 365 was entered on 15.02.1958. Both are described as limestone bowls with flat bases and convex sides. 18 The bowl mentioned in the Catalogue may in fact be Bowl 4, but the object contains the pencil marking “AR 19” on the outside, indicating that it was found in tomb 19 of the Archaic Cemetery, rather than in Cemetery 300.
Figure 1.10 – Archive image of bowl from tomb 365 which is similar to Bowl 4. RMO Archives: Opgravingen Aboe Roasj, 8.2.2/9 a. Date unknown.
Figure 1.11 – Object F.1960/11.221 (Bowl 4).
Figure 1.13. Chronological timetable of Ancient Egyptian Dynasties. Image: John Baines, "Ancient Egyptian Cities: Monumentality and Performance." The Cambridge World History: 27-47: 28. doi:10.1017/cho9781139035606.004.
Figure 1.12 – Entry in the Catalogue of Objects describing a “cream-coloured, black spotted limestone bowl.” RMO Archives: Opgravingen, Aboe Roasj, 1958, Box 3 8.2.2/2j- 3e, folder 8.2.2/3a, pp. 4.
Figure 1.14. Map of Egypt showing Abu Roash. Image: Baines, “Ancient Egyptian Cities”, 29.
Figure 1.15. Excavations at Abu Roash. RMO Archives: Opgravingen Aboe Roasj, 8.2.2/9 a. Date unknown. Figure 1.16.Objects excavated in situ in a fully excavated tomb. Tomb 893. 1959 excavations. RMO Archives: Opgravingen Aboe Roasj, 8.2.2/9 a.
1.3. Description of Phenomena The spots on these objects are dark, covering at least 75% of the surface area of the bowls. They range in size from less than 1mm, to smudges (irregular dark blemishes) measuring up to 6.5cm in diameter. The spots vary in shape, and colour. Some have offshoots and growths, (largest spot in Figure 1.17) whereas others are more circular in shape (smaller spots in Figure 1.17). Colours can range from dark brown, gray, or black (Figure 1.18). At first inspection, the spots appeared to only affect the surface of the stone by forming superficially. No damage to the stone substrate can be seen around the spots 1.3.1 Typology of spots In order to gain a fuller understanding of the spots, a larger survey was conducted of nineteen other objects from the RMO collection that exhibit the same phenomena. Each bowl was measured, photographed and visually examined for the frequency, colour, shape and size of the dots appearing on them. The frequency of the spots was visually measured using three categories: Light, Medium and Heavy coverage. Light coverage was categorized as minimal coverage of object surface, large areas being unaffected (Figure 1.19). Medium coverage occurred where there were larger areas of surface coverage, with larger groupings of spots and fewer areas on the surface unaffected (Figure 1.20). Heavy coverage occurred where there were large groupings of spots, with little to no areas on the surface being unaffected (Figure 1.21). Each object from the RMO survey selection Figure 1.17. Example of spot with offshoots. Detail, object F.1961/1.163. Figure 1.18. Detail, F.1960/11.221 showing various sizes, shapes and colours.
was inspected and placed into one of the three categories. The results can be seen in Table 1.1. 19 The examination of the RMO survey objects presenting this phenomenon was an attempt to shed light on the growth patterns of the spots to see if growth was more present on the outside or the inside, if spot types were exclusive to certain objects. 19 It should be noted that the frequency of the spots on the objects in the RMO survey selection was not investigated as the survey was only used to create a typology of the spots and to compare their appearance with the core objects of this research. Figure 1.19. (top left) Example of bowl with light spot coverage. RMO Survey Selection F.1960/12.355. Figure 1.20. (top right) Example of bowl with medium spot coverage. RMO Survey Selection F.1960?11.195. Figure 1.21. (left) Example of bowl with heavy spot coverage. RMO Survey Selection F.1961/1.196.
Table 1.1. RMO Survey Selection Spot Frequency Classification. F. 1960/12. 244 F. 1960/12. 349 F. 1960/12. 311 F. 1960/11. 195 F. 1960/11. 184 F. 1961/1. 183 F. 1960/11. 177 F. 1960/12. 347 F. 1960/12. 355 F. 1961/1. 196 F. 1961/1. 210 F. 1960/11. 220 F. 1960/11. 190 F. 1960/12. 343 F. 1960/12. 331 F. 1960/11. 170 F. 1960/12. 370 F. 1960/12. 363 F. 1961/1. 144 To ta l O bj ec ts Light 11 Medium 7 Heavy 1 Using the same criteria, the four bowls that are the focus of this study were also visually examined and categorized in Table 1.2. Table 1.2. Thesis Selection Spot Coverage. F. 1960/1. 188 F. 1960/11. 196 F. 1960/11. 221 F. 1961/1. 163 To ta l O bj ec ts Light 1 Medium 1 Heavy 2 Together with the frequency categorization, the objects were optically examined to create a typology of the spots appearing on the surface. This typology was created to identify different spot shapes and to determine if their shape was related or not to variations in formation. The spots were categorized into eleven distinct types with two types having sub-types. The type names were based on visual characteristics and where possible, taken from commonly used terminology. The spot types and descriptions are found in Table 1.3.20 Table 1.3. Spot Types and Descriptions
Photo Spot Type Description
Black Circle Circular, or near circular. Does not contain any offshoots or irregularities. Star Starburst or snowflake in appearance. One singular spot with multiple branches (minimum three) and offshoots radiating from the center. 20 For a fuller table including larger image references of each spot, see Appendix V: Spot Typology.
Double Star Same as above, but with a double ring. Central core is dark, with offshoots and branches radiation out, followed by a lighter section, encircled by another ring of darker offshoots. Final ring may or may not be complete. Shooting Star Small spot with one singular directional offshoot, usually the diameter of the spot. Colour fades as it goes away from the original spot. Can be going in any direction. Tail may also split in two once leaving the main spot, but tails are still in a similar direction. Halo • Black • White Black Halo- central black circular shape surrounded by a lighter brown/black ring. Ring may be irregular in shape. White Halo- central black circular shape, surrounded by a light, almost white ring. Shadow Light, faded appearance of a marking on the stone surface. May consist of any of the typologies. Watermark Long, stain-like marks. Similar to a smudge but with refined lines. Usually appearing near the edge of the object. Smudge • Black • Brown • Grey An irregular, broad or elongated indefinable shape. Much larger than any other spots. Can include other spot types within the smudge. Ring Deposit usually black in colour with a lighter centre, creating a dark ring on the surface. Irregular Any spot or marking that does not conform to the other classifications. Can be a multitude of shapes, sizes and colours.
Pinprick Small black dots, appearing to be no larger than a pinprick or microdot. Once this typology was created, the spots were identified on each object in the survey selection. A table was created indicating which types appeared, where the spots were found, and the amount of spot coverage on the object.21 This table was then used to create a chart, indicating the frequency of each spot type within the survey selection (Table 1.4.). 22 Table 1.4. Spot Types on RMO Survey Selection Objects F. 1960/12. 244 F. 1960/12. 349 F. 1960/12. 311 F. 1960/11. 195 F. 1960/11. 184 F. 1961/1. 183 F. 1960/11. 177 F. 1960/12. 347 F. 1960/12. 355 F. 1961/1. 196 F. 1961/1. 210 F. 1960/11. 220 F. 1960/11. 190 F. 1960/12. 343 F. 1960/12. 331 F. 1960/11. 170 F. 1960/12. 370 F. 1960/12. 363 F. 1961/1. 144 Oc cu rr en ce s Star 15 Pinprick 19 Watermark 6 Black Circle 18 Smudge 17 Halo- Black 15 Halo- White 12 Ring 7 Double Star 14 Irregular 17 Shooting Star 7 Shadow 11 After the typology was completed, a chart was also created for the four bowls that are the focus of this case study for comparison (Table 1.5.). 21 The full table with object images and details can be found in Appendix III: RMO Survey Selection Photos, and Appendix IV: RMO Survey Selection Typology. 22 The Halo-Black and Halo-White sub-types were separated into their own lines for this table, as they do not always appear together on objects, and are visually different. Black Halos can range in size, whereas white Halos tend to be much smaller in size. There are also ten objects in the RMO survey selection that do not exhibit Halos- either one type or both. Smudge colours were not separated as they appear on all but two objects from both the RMO survey selection and the four case study bowls. Smudge shape, size and colour vary, but as other spot types are normally found within the smudge, these differences do not indicate a need for the separation of colours in the table.
Table 1.5. Spot Types on Thesis Selection Bowls F. 1960/1. 188 F. 1960/11. 196 F. 1960/11. 221 F. 1961/1. 163 Oc cu rr en ce s Star 4 Pinprick 4 Watermark 2 Black Circle 4 Smudge 4 Halo- Black 4 Halo- White 4 Ring 4 Double Star 4 Irregular 4 Shooting Star 4 Shadow 4 Discussion and Conclusion The frequency of spots in the RMO survey selection was mostly light, with eleven of the nineteen objects having light frequency. Only one object (F.1961/1.196) was categorized as having heavy frequency (Figure 1.21).23 Each object in the RMO survey selection presented a unique collection of spots. Only one object (F.1960/11.184) possessed all twelve spot types (Figures 1.22 and 1.23). The most common spot types in the survey selection are Pinprick, which affects each object, Black Circle (18 objects), Smudge (17 objects) and Irregular (17 objects). The spots with the fewest occurrences are Shooting Star (7 objects), Ring (7 objects), and Watermark (6 objects). 23 For both recto and verso images of F.1961/1.196, see Appendix III: RMO Survey Selection Photos, Figures 35 and 36.
The four bowls in the case study on average have significantly more spots than the nineteen in the RMO survey selection, with Bowl 2 and Bowl 4 categorized with heavy coverage, and only Bowl 1 categorized with light coverage. Bowl 2 and Bowl 4 exhibited each kind of spot, whereas Bowl 3 and Bowl 1 were only missing a Watermark on the surface.24 It should be noted that the two bowls with a heavy coverage of spots are also the ones exhibiting every category of spot. The same cannot be said for the RMO survey selection as object F.1961/1.196 exhibits eight of the eleven spot types. The only object in the RMO survey selection to exhibit all spot types is F.1960/11.184, although it was categorized as light spot coverage (Figures 1.22, 1.23). Given these observations, the spot types do not correlate with the coverage of the object. Spot shapes and types can possibly indicate origin of growth. For example, Pinpricks suggest a beginning of formation, and Star, Double Star, Shooting Star, Halo, and Ring suggest outward growth from a central point. It is inconclusive as to how the other spot types, such as Smudge or Irregular were formed. The spots are not exclusive to certain objects, nor do they only appear in conjunction with others. Overall, the location of the spots does not reveal any information in regards to their formation, as they were found equally on the inside and outside of the objects. Spots also do not seem to form in conjunction with others, indicating that there is no pattern in growth. The different spot types could be researched in more detail to 24 There is no correlation or relationship with the four bowls chosen for the case study. The bowls were chosen to include a variety of shapes and sizes. Figure 1.22. Object F.1960/11.184 recto. The only survey selection bowl to exhibit all spot types. Figure 1.23. Object F.1960/11.184 verso.
understand how they relate to the development of this phenomenon, but this is outside the remit of this research. 1.3.2. Spot Mapping Using the spot typology, the four bowls in the case study were then studied more closely. Each spot on each object was mapped and colour –coded (Table 1.6) in order to investigate whether the spots formed in any particular pattern.25 If a pattern were to emerge with the spot distribution, or if certain spots formed in conjunction with others, it may aid in the identification of the phenomena that has caused the formation of spots (Figures 1.24, 1.25).26 Table 1.6. Image Mapping Legend Spot Type Mapping Legend Star Pinprick Watermark Black Circle Smudge- Black Brown Gray Halo- Black Halo- White Ring Double Star Irregular Shooting Star Shadow 25 Inkscape graphics editor was used to create the visual mapping of the spots. 26 Larger images of the object mapping can be found in Appendix VI: Object Mapping.
As stated above, nearly every type of spot was found on each of the four bowls. Judging from a visual investigation, the most common spot type was Pinprick, appearing generously on every bowl. The least common spot type is Watermark; only appearing on Bowl 2 with one watermark and Bowl 4 with five. Watermarks were only found on the inside of the bowls. The remainder of the spot types could be found all over each bowl in varying quantities. Each bowl presented a unique compilation of spots. For example, Bowl 4 only had one Double Star, whereas Bowl 2 presented over 60 solely on the inside. In regards to pattern or formation groups, most spot types are more randomly spread over the entirety of the bowl.27 Smudge shape, colour, size and frequency are varied based on the object and no correlation could be made with their formation. Rings are generally found in clusters or in close proximity to one another, though a few solitary outliers can be found such as in Bowl 3 (Figure 1.26). Other spot types can cluster in certain areas such as Stars and Shooting Stars, but the clusters appear all over the objects, presenting the appearance of a general overall spread of the spot type. 27 The spot types being referred to are Pinprick, Black Circle, Halo-Black, Halo- White, Irregular, Shadow, Smudge and Shooting Star Figure 1.24. Image mapping on Bowl 2. Recto. Figure 1.25. Image mapping on Bowl 2. Verso.
Overall, investigation into spot frequency and appearance patterns through image mapping has resulted in the understanding that the placement of the spots on the bowls does not correlate to a specific pattern or in conjunction with any other spot. Although some spot types tend to form in close relation to each other, the overall pattern is random and therefore no proper conclusions regarding the formation of the spots can be made. The spots seem to have formed into different types randomly based on an unknown factor. 1.3.3 Tomb Mapping In order to determine if the burial location of the bowls was related to the formation and frequency of the spots, the four bowls together with the objects from the RMO survey selection were examined for indications and marking of provenance. The tomb markings found on the objects were then mapped onto the plans provided in the excavation report to see if conclusions could be drawn. Three of the bowls in this case study (Bowl 2, Bowl 3 and Bowl 4), and thirteen objects in the RMO survey selection had pencil markings on the stone surface identifying which tomb in which they were found in (Figure 1.27). Using the maps of the cemeteries provided in the Abu Roash excavation report, these tomb numbers were mapped in order to determine if correlations existed between location of burial and the formation of the spots. Objects were separated by cemetery, and locations were studied individually. The finds from each cemetery were then compiled on to the map of the entire site of Abu Roash to assess if the geographical placement of the cemetery had any effect on the state of the artefacts (Figure 1.28). A list of all the objects which had a marking on them and the tomb they were found in can be seen in Table 1.7. Figure 1.26. Cropped and enlarged area of image mapping on Bowl 3, side 4. For full size image, see Appendix VI- Object Mapping, figure 12.
Table 1.7. Tomb numbers found written on objects. Object Number Tomb Number F.1960/1.188 (Bowl 2) 883 F.1960/11.196 (Bowl 3) AR 45 F.1960/11.221 (Bowl 4) AR 19 F.1960/11.170 AR 88 F.1960/11.177 AR 18 F.1960/11.184 AR 64 F.1960/11.195 AR 43 F.1960/12.244 368 F.1960/12.311 431 F.1960/12.331 491 F.1960/12.347 455 F.1960/12.349 402 F.1960/12.355 429 F.1960/12.363 449 F.1961/1.196 892 F.1961/1.210 833 Archaic Cemetery – Season 1957 28 A total of five bowls and one stand (F.1960/11.184) were uncovered in the Archaic Cemetery during the 1957 season. Two bowls originated from the case study (Bowl 3, found in tomb AR45 and Bowl 4 found in tomb AR19), while four artefacts were from the RMO survey selection. All but one was located in the “Archaic Tombs” area, while one bowl (F.1960/11.170) was found was found in an Old Kingdom Tomb to the north. Three were found in close proximity to each other, with F.1960/11.184 and F.1960/11.195 located side by side in tombs AR64 and AR43 respectively. Bowl 3 was excavated two tombs away in tomb AR45. The other two bowls were found 28 For mapped tombs of the Archaic Cemetery, see Appendix VII: Tomb Mapping, Figure 1. Figure 1.27 - Tomb marking in pencil on Bowl 3.
further southeast from the others in tombs AR19 (Bowl 4) and AR18 (F.1960/11.177). The tombs were found scattered throughout the entire cemetery. The objects found in this cemetery exhibited fewer spots on the outside than inside. Apart from Bowl 4, the artefacts have large patches on both sides where no spots are found. Cemetery 300 29 Only one bowl in the selection contained a marking indicating its provenance to Cemetery 300 (F.1960/12.244, found in tomb 368), but the two archival entries describing cream-coloured black-spotted bowls were also from this cemetery (tombs 365 and tomb 343). Tomb 368 and 365 are located next to each other, with tomb 343 located further northeast. All three tombs are located on the south-eastern edge of the cemetery. The spots on the outer surface of object F.1960/12.244 consist mainly of black circles, and small stars. The trend continues on the inside, with the addition of small smudges. Both the inside and outside contain patches where no spots have formed. Cemetery 400 30 A total of 6 bowls were unearthed in Cemetery 400, all originating from the RMO survey selection. Four tombs are located within close proximity to each other (tombs 429, 431, 449 and 453), while the other two (tombs 402 and 491) are located on the outskirts of the cemetery. All tombs with the exception of tomb 491 are located in the north-eastern quadrant of the cemetery. The bowls found in the four central tombs seem to be the least covered in spots from the entire survey collection, exhibiting only scattered black circles and pinpricks spots, with large areas without any accretions. However, the two bowls from the outer tombs do exhibit more coverage of spots.31 There are large areas of pinprick spattering and black dots. Yet in comparison to more heavily covered artefacts, these two are still general unaffected by spot growth. 29 For mapped tombs of Cemetery 300, see Appendix VII: Tomb Mapping, Figure 2. 30 For mapped tombs of Cemetery 400, see Appendix VII: Tomb Mapping, Figure 3. 31 Object F.1960/12.349 found in tomb 402 and F.1960/12.331 found in tomb 491.
Figure 1.28- Abu Roash Southern Cemeteries with tombs mapped in orange. Klassens, Abu Roash, 58.
Cemetery 800 32 The bowls found in Cemetery 800 appear to be the most affected with the spot phenomena. There are three bowls from the sample found in this cemetery; two from the RMO survey selection (F.1961/1.183 found in tomb 892, and F.1961/1.210 found in tomb 833) and one from the case study (Bowl 2 found in tomb 883). All three tombs are located centrally within the cemetery. The insides of each bowl are heavily covered in spots relative to the outsides of the bowls. Discussion and Conclusion Based on observations from the three cemeteries on the overall plan of Abu Roash, artefacts some conclusions can be made. The tombs are located east of the hill, towards the flood plain. The cultivation line is located very close to the Archaic Cemetery and Cemetery 800. Cemetery 300 is also located along the cultivation line, but a Moslem Cemetery now borders it. Due to the arid Egyptian climate, crops have to be irrigated regularly.33 Given this information, the cultivation area at Abu Roash would be quite wet, and the moisture would permeate further into the cemeteries, creating a moist burial environment. The Archaic Cemetery and Cemeteries 300 and 800 are all located closer to the cultivation line, while Cemetery 400 farther away (see Figure 1.28). The placement of these cemeteries in conjunction with the cultivation line may be indicative of the moisture content in the burial soil of the tombs. As the bowls located in the center of Cemetery 400 are the least covered in spots, which is also the area farthest from the cultivation line, it indicates that area was the driest. No bowls in the case study, or in the RMO survey selection were found together in the same tomb, so comparisons could not be made with objects found in conjunction with one another. It must also be noted that this sample is not indicative of the burial conditions of all cemeteries. Further research should be completed with the remaining bowls, as well as any other stone objects found to possess similar spots on their surface to confirm the correlation between spot formation and tomb location made with the artefacts in this selection. The various excavations completed by the French Institute for Oriental Archaeology dating from 1900-2008 have produced many stone and limestone objects, but none 32 For mapped tombs of Cemetery 800, see Appendix VII: Tomb Mapping, Figure 4.
33 Brouwer, C., and M. Heibloem. "Irrigation Water Management: Irrigation Water Needs." Chapter 2: Crop Water Needs. Accessed April 24, 2019. http://www.fao.org/3/s2022e/s2022e02.htm.
have been observed as having black spots. However, the French Institute has focused their excavations at the top of the hill in Cemetery M.34 The spots have been present on the objects since excavation, meaning they formed either before burial or as a result of burial conditions. The placement of the types of spots is not indicative of a formation or growth pattern, although the tombs in which the bowls were placed and their proximity to the river may be a contributing factor in the frequency of spot formation and the surface area the spots cover.
2. The state of the Art: Egyptian Bowls and Spots
2.1. Egyptian limestone bowls 2.1.1. Extent of production Limited information exists regarding the sourcing and quarrying of the stone used for, and the manufacturing of stone vessels in ancient Egypt 35, as excavations have yet to produce detailed information from the archaeological record. El-Khouli (1978) states that stone vessels were one of the most common items amongst funerary furniture placed in ancient Egyptian tombs. 36 Some tombs dating from the first three dynasties (c. 3150-2613 BCE) contained many stone vessels, numbering in the hundreds, sometimes thousands.37 Limestone was the most commonly used stone for the production of stone vessels, and was first used as early as the Naqada I period (4400- 3000 BCE).38 2.2. Limestone 2.2.1. Provenience, quarrying Limestone is comprised mainly of calcium carbonate, with the addition of small quantities of other inclusions such as silica, clay, iron oxide and magnesium carbonate.39 The limestone used for the production of stone vessels in ancient Egypt consists of up to 50% fossils in a matrix of microcrystalline calcite. They can range 34 Personal communication, Dr. Yann Tristant, archaeologist currently in charge of the excavations at Abu Roash. 20 March, 2019. 35 For the purposes of this paper, the period in which ancient Egypt is being referred to is Early Dynastic and Dynastic Egypt before the arrival of Alexander the Great in 332 BCE (c.3150-332 BCE). 36El- Khouli, Ali, Egyptian Stone Vessels, Predynastic Period to Dynasty III. (Mainz: Von Zabern, 1978): vol. I, viii. 37 It should be noted that stone vessels were mostly restricted to the upper classes of Egyptian society, as many stones were not easily accessible, and their manufacture required a high degree of craftsmanship. El-Khouli, Stone Vessels, vol. I, viii. 38 Barbara G. Aston, Ancient Egyptian Stone Vessels- Materials and Forms. (Heidelberg: Heidelberger Orientverlag, 1994): 39.39 A. Lucas, Ancient Egyptian Materials and Industries. (Whitefish, MT: Kessinger Legacy Reprints, 2012): 66.
from microscopic foraminifera to nummulites, which measure up to 2cm in diameter. 40 Limestone quarries were, and still are, abundant in Egypt. Limestone quarries outnumber all other stone quarries in the country.41 Nearly all limestone used for building stones, as well as non-architectural purposes, was quarried from Tertiary formations dating from the Eocene, Paleocene, and Pliocene ages. These quarries are located in the hills and cliffs that border the Nile Valley from Cairo to Isna, 42 a distance of 554 km. Limestone is a ‘soft stone’, and easier to extract than harder stones such as granite and basalt. It is a sedimentary rock, and its ease of availability and workability meant that it was usually quarried and used in the immediate area where building or craftsmanship was taking place. 43 The quarrying of limestone was carried out using various tools. Hard stone tools were most common, though it is known that soft stones were quarried with copper chisels and picks, which were used to cut vertical trenches around three sides of the area to be extracted. The open-faced side was then undercut and the entire block was detached. 44 Although metal tools were used, none have been found during excavation. This is most like due to the fact that metal tools were easily dulled, and the metal was most likely melted down and reused for other purposes. 45 Although limestone was quarried within the immediate surrounding area of where it was to be used, for monumental projects, quarries located further away would sometimes be used to obtain a stone of higher quality as calibre and hardness can differ greatly.46 Based on petrographic studies that have been conducted on Egyptian limestone quarries, some connections can be made between the bowls and their possible provenience. According to a petrological survey conducted by J. A. Harrell (1992), the archaeological site of Abu Roash is located on the Mokattam geological formation. The Mokattam quarry (Figure 2.1) is located in the south-eastern region of Cairo and is believed to be one of the main locations where limestone was sourced for 40 Lucas, Materials and Industries, 35.
41 Rosemary Klemm, “Chapter VII: Materials and Techniques. 1. Stone,” in "Egypt,
Ancient." Oxford Art Online, (2003). doi:10.1093/gao/9781884446054.article.t025075 42 J. A. Harrell and Per Storemyr, “Ancient Egyptian Quarries- an Illustrated Overview” In Abu-Jaber, N., Bloxam, E.G., Degryse, P., and Heldal, T. (eds.) QuarryScapes: Ancient Stone Quarry Landscapes in the Eastern Mediterranean, Geological Survey of Norway Special Publication, 12 (2009): 17. El- Khouli, Stone Vessels, vol. II, 793. 43 Aston, Stone Vessels, 37. 44 Harrell and Storemyr, “Ancient Egyptian Quarries”, 29. 45 Elizabeth Bloxam,2010, Quarrying and Mining (Stone). In Willeke Wendrich (ed.), UCLA Encyclopedia of Egyptology, Los Angeles. Accessed February 28, 2019. http://digital2.library.ucla.edu/viewItem.do?ark=21198/zz0026jkd5 pp. 4. 46 Lucas, Materials and Industries, 66.
ancient Egyptian constructions.47 The limestone found in the Mokattam formation is fine-grained and sandy. The stone may also contain mudstones, wackestones and packstones with inclusions that are mainly globigerinids, small amounts of nummulitids and echinoids. 48 These inclusions are fossiliferous microsparites and biomicrosparites, which are forms of calcite that contains minute spar crystals.49 While the limestone used to make the bowls from Abu Roash may not be from the Mokattam quarry50, the site is located in close proximity to it, meaning the stone may be similar in composition.51 From looking at the map provided by Harrell (1992), the limestone bed located near Abu Roash is also of the Mokattam group, so there is a high chance of similar composition. Figure 2.1. Mokattam Quarry. Park, Shin, “Mokattam Limestones”, 190. Photographer unknown. In a study undertaken by H.D. Park and G.H. Shin (2009), the total porosity of Mokattam samples was found to be 24%.52 This porosity level indicates that it is not a dense stone, therefore allowing moisture to enter the substrate. If this analysed
47 H. D. Park, and G.H. Shin. "Geotechnical and Geological Properties of Mokattam Limestones: Implications for Conservation Strategies for Ancient Egyptian Stone Monuments." Engineering
Geology104, no. 3-4 (2009): 191. doi:10.1016/j.enggeo.2008.10.009.
48 J. A. Harrell, "Ancient Egyptian Limestone Quarries: A Petrological Survey." Archaeometry34, no. 2 (1992): 195-211. doi:10.1111/j.1475-4754.1992.tb00492.x.
49 "Microsparite - Oxford Reference." Microsparite - Oxford Reference. June 16, 2017. Accessed May 25, 2019. https://www.oxfordreference.com/view/10.1093/oi/authority.20110803100156478. 50 The quarry is located on the opposite side of the Nile from Abu Roash. 51 Detailed images of Mokattam limestone were not available from academic sources to make a visual comparison with the Abu Roash bowls. Further petrographic analysis of the bowls would need to be undertaken in order to make a proper comparison. 52 Park, Shin, “Mokattam Limestones” 196.
Mokattam sample is indicative of the limestone used to make the Abu Roash bowls, they would have been susceptible to water absorption while buried. It should be noted that Bowl 3 has a pink hue, and Bowl 2 has one section on the back, which is yellow/orange. These pink and yellow tints have been attributed to weathered rock, and the presence of hematite53 has also been known to produce a pink or red colour in the stone.54 These bowls may have come from different quarries than the other two, but the differences in colour may also be attributed to areas in the quarry that were more weathered, or a certain area where hematite was present. 2.2.2. Production technique Given their large scale of production, there is a surprising lack of information about the manufacture of these vessels. 55 A few tomb scenes, produced after the Third Dynasty, depict a visual representation stone vessels being manufactured, including the drill used. The drill itself is also depicted as a hieroglyph that is used in front of words to denote a ‘craft’ or ‘art’ (Figure 2.2). 56 Figure 2.2. Crank drill or borer hieroglyphs from Gardiner’s (1957) signs U24 and U25. Alan Gardiner, Egyptian Grammar: Being an Introduction to the Study of Hieroglyphs. Oxford: Griffith Institute, Ashmolean Museum (1957): 518-519. Once the stone was quarried, it was then worked and fashioned into the desired object. The exact method for manufacturing stone vessels in the Pre-and-Early Dynastic period is unknown. The first depictions of the process date to the Fifth Dynasty, in two tombs at Saqqara (Figure. 2.3). 57 Based on these later depictions in stone carvings, unfinished vessels excavated at various sites, the aforementioned hieroglyphic symbol, and knowledge from other civilizations, archaeologist Denys Stocks has undertaken various experiments by studying vessels and written records in order to recreate the tools used in ancient Egyptian stone-working and discover 53 Iron oxide present in ore (Fe203). 54 Harrell, “Egyptian Limestone Quarries” (1992), 205. Aston, Stone Vessels, 35-36. 55 El-Khouli, Stone Vessels, vol. II, 789 56 Ibid, Denys Stocks, Experiments in Egyptian Archaeology: Stoneworking Technology in Ancient Egypt. London: Routledge, (2003): 17. 57 Stocks, Experiments in Egyptian Archaeology, (2003): 17.
the methods of the craft.58 Tools were fashioned using authentic materials, and various forms were attempted to recreate Egyptian stone vessels. The tool used to bore into and hollow out stone was a forked tree branch with a copper tube fitted on its lower end. Two stone weights were attached under the fork. This was then drilled into the stone to create a void inside. Once that was complete, a second forked branch was inserted. This time, the branch was inverted, with stone borers of various shapes attached to create the desired opening in the vessel (Figure 2.4). For both the original tubular drilling, and the stone boring, sand was used as an abrasive. 59 58 Stocks, Experiments in Egyptian Archaeology, pp. 18. 59 Ibid. Figure 2.3. An Old Kingdom relief from Saqqara depicting the manufacture of stone vessels. Drawing by P. Der Manuelian 1915. Photo courtesy: Ilan, David. 2016. “The Ground Stone Components of Drills in the Ancient Near East: Sockets, Flywheels, Cobble Weights, and Drill Bits”. Journal of Lithic Studies 3 (3), 261-77. Figure 2.4. Depictions of the crank and drill components. (Stocks, Stoneworking, 2003, 137).
Limestone could have also been shaped from blocks using copper tools, but sharper, harder materials such as flint scrapers would have been used for more detailed work in hard to reach areas in more complicated vessels.60 Once the shape and overall form was complete, the surface was smoothed and polished, usually with stone tools, using sand as an abrasive.61 2.3. Possible Sources of the Spots At the beginning of this research, it was unclear whether the black spots were of organic or mineral origin. Both have the potential to appear visually similar to the other. For this reason, both options were thoroughly investigated based on the visual appearance of the spots, and into the environment required for their formation. 2.3.1. Biological Growth on Stone Biological growth on stone, while adding to the overall patina of an ancient work of art, has the potential to cause serious damage to the stone substrate. When discussing biological growth on stone, there are two main terms to consider: biodeterioration and bioreceptivity. Biodeterioration was first defined by Hueck (1965) as “any undesirable change in the properties of a material caused by the vital activities of living organisms.”62 Bioreceptivity is defined as “the aptitude of a material to be colonized by one or several groups of living organisms without necessarily undergoing any deterioration.”63 The bioreceptivity of stone is dependent on its structure and chemical composition, and the potential amount of biological activity is determined by the environment and climatic conditions in which it is located. 64 In addition to environmental conditions, bioreceptivity can also be determined by the availability of water on the stone surface and the absorption potential (ie. porosity and capillary action) of the material. 65 Stones with a more open porosity and higher values of capillary action are therefore more susceptible to biological colonization. All stone material is bioreceptive, and able to be colonized by biological organisms. 66 In regards to limestone, the porosity of the stone can vary depending on the classification. Some 60 Stocks, Stoneworking (2003), 141. 61 Paul T. Nicholson and Ian Shaw, Ancient Egyptian Materials and Technology, (Cambridge: Cambridge University Press, 2009): 65. 62 H. J. Hueck, The Biodeterioration of Materials as Part of Hylobiology. Mater. Org. 1 (1), (1965) 5-34. 63 A. Z. Miller, et. al.,"Bioreceptivity of Building Stones: A Review." Science of The Total Environment 426 (2012): 3. 64 Th. Warscheid, and J. Braams. "Biodeterioration of Stone: A Review." International Biodeterioration & Biodegradation46, no. 4 (2000): 343. 65 Miller, “Bioreceptivity”, 8. 66 Miller, “Bioreceptivity”, 3, 9.
formations, such as chalk, are very porous, whereas others such as carboniferous limestone are impermeable.67 68 There are various forms of biological growth that can occur on stone. Based on visual inspection of the Abu Roash bowls in conjunction with the research undertaken into biological deterioration on stone, there are three main types that could make up the composition of the black spots. 2.3.1.1 Fungi Fungi are heterotrophic organisms that greatly contribute to the deterioration of stone. There are two main categories of fungi: epilithic, which live on the surface of the stone, and endolithic, which live inside pores and fissures.69 The black spots on these limestone bowls strongly resemble black fungi. Black fungi tend to form small black colonies and often occur alongside lichens.70 They have thick cell walls, making removal difficult, and can cause bio-pitting, which is the formation of lesions of up to 2cm in diameter and depth into the stone,71 as well as cause staining, appearing as dark spots,72 mineral dislocation, and dissolution (Figures 2.5, 2.6).73 67 "The Movement of Water Through Limestone." The Movement of Water Through Limestone | What Is Limestone? | Limestone Landscapes | Geology of Britain | British Geological Survey (BGS). Accessed May 23, 2019. https://www.bgs.ac.uk/discoveringGeology/geologyOfBritain/limestoneLandscapes/whatIsLimesto ne/waterMovement.html. 68 The limestone classification of the bowls from Abu Roash will be touched on lightly but not fully investigated in this paper, as the main focus is the composition and identification of the black spots. 69 Katja Sterflinger, "Fungi: Their Role in Deterioration of Cultural Heritage." Fungal Biology Reviews24, no. 1-2 (2010): 49. 70 Sterflinger, “Fungi”, 51. 71 Ibid. 72 Guilia Caneva, Maria Pia. Nugari, and Ornella Salvadori. Biology in the Conservation of Works of Art. Roma: ICCROM, 1991. pp. 92. 73 Scheerer, Stefanie, et. al. "Chapter 5: Microbial Deterioration of Stone Monuments—An Updated Overview." Advances in Applied Microbiology, (2009), 122. Figure 2.5 and Figure 2.6- Limestone surfaces covered with fungi. Salvadori, “Role of Lichens and Fungi,” 41.
It has been theorized that black meristematic fungi, also called microcolonial fungi, are the most reactive in the deterioration of stone as they can grow on exposed stone with a limited supply of carbon.74 Through their metabolic processes, fungi produce acids such as oxalic, nitric, carbonic, citric, and acetic acid. These can act as chelators, degrading the surface of the stone.75 Despite their potential detrimental effects, citric and oxalic acid may not pose as much of a threat to calcareous stones, as they will react with the stone and create protective layers. Carbonic acid can react and form calcium bicarbonate, a weak alkali buffer, whereas oxalic acid forms calcium oxalateor malonate films, which may have a protective, respectively.76 It should be noted that carbonic acid also has the ability to dissolve insoluble calcium and magnesium carbonates of limestone and other substrates, as it forms calcium and magnesium bicarbonates, which are more soluble.77 2.3.1.2. Lichen Lichens are autotrophic organisms comprising of an interdependence between microscopic alga (such as cyanobacteria), and fungi. Within lichens, the algal cells are interwoven amongst the fungal hyphae and synthesize carbohydrates off which the fungus can thrive, while the fungus contributes to the protection of the more vulnerable algae, secretes minerals for the algae to consume, and absorbs water for further metabolism.78Similarly to fungi, lichens can be either epilithic or endolithic. They can also produce acids such as carbonic and oxalic acid. Oxalic acid production increases with the age of the lichens, and is more active in calcicolous species. The acid, with its aforementioned chelating and acidic trademarks, can cause surface etching, and form pits beneath the thalli (Figure 2.7). 79 Physical deterioration can occur as well due to the expansion and contraction of the thalli upon wetting and drying. This can cause granular loss of stone.80 J.P. McIlroy and Salvadori have suggested that lichens may provide a protective effect on the weathering of limestone, as they can act as a buffer between rainfall, wind, thermal stress, and pollution, which limits particle detachment.81 74 Ornella Salvadori, and Annalaura C. Municchia. "The Role of Fungi and Lichens in the Biodeterioration of Stone Monuments." The Open Conference Proceedings Journal 7, no. Suppl 1: M4 (2016): 41. 75 Salvadori, “Role of Fungi and Lichens,” 40. 76 Sheerer, “Microbial Deterioration,” 111. 77 Caneva, Biology, 31. 78 Caneva, Biology, 169-70, Warscheid, pp. 347- 348. 79 Caneva, Biology, 97. 80 Salvadori, “Role of Fungi and Lichens,” 43-44. 81 J.P. McIlroy de la Rosa, et. al. "The Effects of Lichen Cover upon the Rate of Solutional Weathering of Limestone." Geomorphology220 (2014): 81- 92. pp. 47.
2.3.1.3. Cyanobacteria Cyanobacteria (Figure 2.9) are surrounded by a thick, gelatinous sheath, which is able to absorb and retain water for extended periods of time. This allows them to survive under extreme conditions.82They can form biofilms and crusts onto stone surfaces, which can vary in colour depending on the environment they are found in, and as they are phototrophs, they do not require organic material to grow.83 Cyanobacteria may be the most influential with the weathering of exposed stone as they cause both physical and chemical damage from the excretion of acids and chelating agents.84 82 Caveva, Biology, 94. 83 Sheerer, “Microbial Deterioration,” 112. 84 Sheerer, “Microbial Deterioration,” 117. Figure 2.7- Lichen colonization on limestone causing pitting underneath. ICOMOS Illutsrated Glossary of Stone Deterioration Patterns, 41. Figure 2.8- Lichen on pink limestone in Edzna, Campeche, Mexico. Gaylarde et. al, "Lichen-like Colonies of Pure Trentepohlia on Limestone Monuments." International Biodeterioration & Biodegradation58, no. 3-4 (2006): 120. Figure 2.9- Example of cyanobacteria on stone. Popović, et. al., "Diversity of Terrestrial Cyanobacteria Colonizing Selected Stone Monuments in Serbia." Studies in Conservation63, no. 5 (2018): 294.
2.3.2. Manganese Dendrites Consultation with Dr. Michaela Schmull, Lichenologist and director of collections at the Harvard University Herbaria and Libraries, brought to light the possibility of these spots not being of organic origin. Although the shape appears to be an imprint of a lichen thallus, the thallus would have decayed in the ground over time and would not have left a residue like these spots. Also, given that the objects were buried underground for an extended period of time, lichens should be excluded as they are a symbiosis between fungi, algae and/or cyanobacteria and the latter two require sunlight to survive when associated in lichens.85 With the identification of the spots as organic growth in question, further experts were contacted. Upon consultation with Dr. Liam McNamara, the Lisa and Bernard Selz Curator for Ancient Sudan and Egypt at the Ashmolean Museum in the United Kingdom, and James A. Harrell, professor emeritus of Geology at the University of Toledo, it was suggested that these black spots were not of biological origin, but rather manganese dendrites.86 The Ashmolean museum has two objects, which also contain spots of this nature which have been classified as dendrites: the mace head of a scorpion king (AN1896.1908.E.3632) dating from c. 3100-3000 BCE (Figure 2.11 and 2.12),87 and the carved limestone statue of King Kasekhem (AN1896-1908 E.517) dating from the Second Dynasty (c. 2775- c. 2650 BCE) (Figure 2.10).88 In keeping with this suggestion, as well as taking the doubts of Dr. Schmull into account, manganese dendrites were researched further as a possible identification for the spots. 85 Personal communication, Dr. Mihaela Schmull, Harvard University. 23 April, 2019. 86 Personal communication, Dr. Liam McNamara, and Dr. James A. Harrell, 23 April, 2019. 87 "Mace Head of a Scorpion King." Ashmolean Museum. Accessed April 23, 2019.
https://www.ashmoleanprints.com/image/803569/mace-head-of-a-scorpion-king.
88 "Carved Limestone Statue of King Khasekhem." Ashmolean Museum. Accessed April 23, 2019. https://www.ashmoleanprints.com/image/453746/carved-limestone-statue-of-king-khasekhem.
Figure 2.10- (left), statue of King Kasekhem. Ashmolean Museum, University of Oxford. Figure 2.11- (right), Mace head of a Scorpion King. Ashmolean Museum, University of Oxford. 2.3.2.1 Composition A dendrite is defined as “a surficial deposit of an oxide… that has crystallized in a branching pattern”.89 Manganese dendrites are black or red-brown mineral deposits of manganese oxide and other accessory minerals, often found on limestone and other sedimentary rocks.90 Manganese (Mn) is the third most abundant metal and
89 Julia A. Jackson, Robert Latimer. Bates, and Margaret Glossary of Geology. Gary. Glossary of Geology. Falls Church, VA: American Geological Institute, (1980): 165-166.
90 B. Chopard,, H. J. Herrmann, and T. Vicsek. "Structure and Growth Mechanism of Mineral Dendrites." Nature353, no. 6343 (1991): 409. doi:10.1038/353409a0.
Figure 2.12- Detail of Mace head of a Scorpion King. Ashmolean Museum, University of Oxford.
