Structure Features, Damage and Treatment of Two Pottery artifacts from Tel El-Shobak, Qalyubia, Egypt: Case Study

The research paper aims to identify structure features, damage and treatment of two pottery artifacts from Tell Al-Shobak in Qalyubia, "one of the archaeological sites dating back to new kingdom". Polarized Microscopy "PLM", Scanning Electron Microscope with Energy dispersive X-ray unit "SEM-EDX", X-Ray Diffraction analysis "XRD", and Differential thermal analysis "DTA" were adopted for investigating and analyzing pottery sherds. The research identied structure features proving that the used clay is Nile clay, the additives are sand, grog and calcite. The formation technique is potter wheel .The surface treatment is slip layer. The ring atmosphere is oxidizing. Firing temperature might be about 726.78°C The rst pottery vessel and 737.80°C for the second pottery plate. Research also proved that pottery pieces suffer from various damage aspects such as soil deposits, stains, cracking, fracture, loss of some parts, lack of durability, weakness, and salt crystallization. The studied pottery pieces treated using mechanical cleaning method and chemical cleaning using a mixture of acetone and toluene at a ratio of 1:2 respectively to remove clay soil deposits. EDTA applied to remove lime deposits. Hydrogen peroxide20 % was used to remove soot. Nano Silica 1% was applied to strengthen archaeological pottery .Assembling the pottery sherds was done by Paralloid B72 50%. Replacement pottery sherds conducted by Microballoon and grog in a ratio of 2:1, respectively. After treatment, the pottery artifacts were ready for museum display.


Introduction
Tell al-Shobak is located near the city of Shebin el-Qanater, northeast of Banha; Qalyubia Governorate, Egypt [1].The governorate includes some archaeological sites such as Tell Atrib, Tell el-yahudiyah and Tell al-Shobak [2], which represents the eighth region of the Lower Egypt provinces [3]. Excavations have revealed many pottery artifacts [4].The excavated pottery pieces suffer from various damage manifestations such as soil sediments, cracking, crystallization of salts, various stains, fractures and loss of some parts [5] which requires examination, analysis, restoration and maintenance based on the results of examinations and analyzes. Restoration and treatment methods depend on damage condition of pottery pieces. Choosing appropriate cleaning method is not an easy and simple process due to multiplicity and diversity of used materials for restoration, treatment, and maintenance. This process has become one of the important topics in the eld of treatment [6].Many different cleaning materials used depending on the damage. Among modern used materials in cleaning process recently are carbogel [7]. EDTA used to remove various lime deposits (Orabi and [8], organic solvents for removal soil sediments [9]. Hydrogen peroxide applied to clean soot [10], di chloro methane give the same result [11]. Nano-micro emulsions cleansers are liquid, stable and transparent O/W micro emulsions [12]. Most of the pottery artifacts have a weak physical structure, which requires strengthening by one of the appropriate consolidants, whether acrylic, silicon, acrylic-silicon, or nano composites. In the past few years, nano composites used to strengthen the pottery objects. Some nano materials were added to acrylic and silicon polymers in order to improve their physicochemical and mechanical properties, where it achieved a signi cant improvement in the ability of those polymers to strengthen the pottery [13] . Pottery or glass pieces are subject to breakage and the loss of some parts due to burial soil [14] , weak internal structure and internal pressures impact [15] , or as a result of pressures and external loads [16] . Such pieces need assembly and completion processes. These processes are complex technical techniques [17] .The adhesive and completion materials have varied based on their physical and chemical nature [18]. The materials used in cleaning, strengthening, assembling and completing have varied according to experimental studies in the eld of treatment. Therefore, this study aims to present strategies of treatment of pottery artifacts extracted from Tell Al-Shobak in Qalyubia according to results of examinations, analyzes and damage manifestations proven by research.

Study materials
Three pottery samples were selected, including (2) pottery samples, as well as one sample of site soil.
Those samples used in examinations and analysis that conducted in the research.

Study Methods: Visual Examination
Visual examination is one of the important methods that show pottery archaeometric features and damage manifestations by using different lenses " 4 X: 6 X" or USB digital microscope [19].

Examination by polarizing microscope
Polarizing microscope used to study petrographic aspects and ring conditions, additives and damage of mineral components of archaeological pottery [20]. Thin section of pottery sherds were prepared for petrographic examination using polarizing microscope "Olympus BX51 TF japan attached with digital camera under magni cation 4X up to 40X". It conducted at faculty of Science, Cairo University.

Examination by scanning electron microscope with EDX unit
Scanning electron microscope describes surface morphology and damage aspects [21]. The pottery samples examined by JEOL JSM-840 and SEM Quanta 200 FEG, XTE 325/D8395, the operating conditions were "20 kV and 1 × 10 -9 A".This examination carried out by an environmental scanning electron microscope equipped with an EDX unit at Geological Survey Authority in Cairo.
Analysis by X-Ray Diffraction Method X-ray diffraction analysis is one of the important methods that gives mineral composition of pottery, which helps to identify archaeometric features, and damage manifestations [22]. The device is Philips; the diffraction pattern is between "4-70° 2θ". The operating conditions carried out using Cu-K α radiation 40 MA, 45 kV, this analysis conducted at National Research Center in Cairo Thermal Analysis DTA analyses was performed using Shimadzu-simultaneous thermal analysis type DTA-50 to determine the ring temperature of our samples and evaluate thermal materials characterization.it explains how individual minerals change during a gradual increase in temperature after heating the sample in approximately 1000 °C [23].

Visual Examination:
The visual examination of the pottery pieces proved presence of soil sediments, crystallization of salts, soot, fracture, breaking, fragments and loss of some parts ( Fig. 1A -B).
PLM examination for another part shows semi-circular and sharp-angled quartz grains, as well as presence of grog, calcite, plagioclase, pyroxene, lime deposits and internal cracks in matrix rich in iron oxide (Fig. 4).
PLM of the second pottery sample shows semi-circular and acute-angled quartz grains, calcite, biotite and muscovite, polycrystalline quartz grains and iron oxide (Fig. 5). It also shows presence of semicircular and acute-angled quartz grains, as well as polycrystalline quartz grains, limestone powder, plagioclase, some internal cracks, and iron oxide (Fig. 6).
For the same pottery sample shows presence of polycrystalline quartz grains, limestone powder, plagioclase, biotite, muscovite, lime deposit and iron oxide (Fig. 7) Examination and analysis by SEM-EDX Examination by Scanning Electron Microscope SEM Examination of the rst pottery sample shows that the sample suffers from various damage aspects such as phenomenon of cracking, some stains, quartz grains, and peeling off slip layer ( Fig. 8a). SEM Examination also shows phenomenon of cracking, gaps and crystallization of salts (Fig. 8b).
SEM Examination of the second pottery sample shows presence of fractures, cracks, gaps ,exfoliation of slip layer and salt crystallization ( Fig. 9a).
SEM of the same sample also shows phenomenon of crystallization of salts, gaps, cracks and coarse quartz grains (Fig. 9b)

Scanning Electron Microscope Analysis
The results of EDX analysis of three pottery samples from tell Elshobak, Egypt clari ed presence of carbon, oxygen, uorite, nickel sodium, magnesium, aluminum, silica, Molybdenum, sulfur, chlorine, potassium, calcium, titanium, and iron oxides. These EDX analytical results for three pottery sample ( Fig.  10a-d) and (Table 1).

X-Ray Diffraction Analysis
Three samples were analyzed, including two pottery samples and one sample from the soil of the archaeological site, where X-ray diffraction pattern of the rst sample shows the presence of hematite, quartz, albite, calcite and gypsum as in gure (Fig. 11) and (Table 2 ) . X-ray diffraction pattern of the second sample con rmed presence of quartz, albite, calcite and gypsum as in gure ( Fig. 12) and ( Table  2 ). The analysis of the third soil sample of tell al-Shobak in Qalyubia proved presence of quartz, albite and calcite, as in gure ( Fig. 13 ) and (Table 2 ) .It is clear from the results of the X-ray diffraction pattern that the soil is sandy clay rich in salt.  (Fig. 14). Differential thermal analysis "DTA" of the second pottery sample showed minerals changes in ring temperature from 294.72°C to 408.56°C., the minerals changes increased from 479.89°C to 737.80°C, the stability of the mineral changes from 737.80°C to 1000°C. The results of mineral changes indicated that the ring temperature might be about 737.80°C (Fig. 15).

Discussion Of Results
The visual examination of the pottery pieces from tell el-Shobak in Qalyubia, Egypt showed that the pottery samples formed by potter wheel method. It also shows soot, salts, cracking, lost parts and surface sediments as shown in ( Fig. 1a-b). Damage aspects were due to heterogeneity of mineral components [24]. Some researchers attributed the damage to burial in the soil [25] .The exposure environment (post excavation) increases severity of damage [26]. Polarized microscope proved that the used clay is Nile clay due to presence of biotite, muscovite, pyroxene and plagioclase [27] as shown in ( Fig. 2:7). PLM examination con rmed presence of some additives such as sand, lime stone powder and grog, which are common materials in Egyptian pottery [28] as shown in ( Fig. 2:7). PLM examination also proved presence of surface treatment by slip layer. Sometimes, the ancient Egyptian used red wash [29]. The examination also showed presence of some internal cracks due to pressures and strains. Pottery texture was coarse for the rst sample and medium to coarse for the second sample as in Fig. (2:7). The texture is shape and relationship of the granules to each other [30]. The texture varies according to clay, formation technique, surface treatment, and ring [31]. SEM Examination showed presence damage aspects, such as cracks, gaps, fractures, crystallization of salts and stains, as in shown in ( Fig. 8a-b &9a-b.( Cracks in our studied pottery are due to internal pressures and crystallization of salts [32]. SEM-EDX con rmed medium burning of the rst pottery for presence of carbon dioxide with a high percentage 15.17% for the surface area and low percentage 1.95% for the core area. Good burning for the second pottery sample, where the percentage of carbon reached 1.78% for the surface and 0 .66% for the core area. This indicates that the burning atmosphere was oxidizing atmosphere for pottery samples, as shown in (Table 1).SEM-EDX con rmed presence of calcite, chloride, and sulfate salts, where the percentage of chlorine in the rst pottery sample reached 16.19% for the surface and 4.45% for the core. For the second sample, the percentage of chlorine reached 4.46% for the surface as shown in (Table 1). EDX also proved presence of calcium, where the percentage of calcium in the rst pottery sample reached 9.43% for the surface and 8.25% for the core. For the second sample, the percentage of calcium reached 14.77% for the surface and 6.48% for the core as shown in (Table 1). The percentage of sulfur in the rst pottery sample reached 3.13% for the surface, while the percentage of sulfur in the second pottery sample reached 3.43% for the surface, which con rms presence of chloride and sulfate salts as shown in (Table 1). The crystallization of salts is one of the most important manifestations of damage because pottery artifacts is a hygroscopic material that absorbs saline water from the soil [33].XRD proved presence of calcite as one of the temper additives [34]. The analysis also proved presence of gypsum and carbonates due to burial soil [35]. XRD analysis also revealed presence of albite, quartz and calcite in the archaeological site sample, which con rms that the soil is calcareous clay soil as shown in (Table 2). Differential thermal analysis "DTA" of the rst pottery sample showed the ring temperature was 726.78°C for the rst pottery, where the hydroxyl group of mechanical combined water for clay was lost at ring temperature from 31.21. °C to 79.60°C. The minerals changes increased by hydroxyl group loss of chemical combined water of clay, burning and oxidation of organic matter from 109.80°C to 164°C and then the minerals changes were signi cantly increased due to decomposition of carbonate into CaO and Co2, organic residues and chlorides from 388.83 to726.78 (Fig. 14) .for the second pottery, the ring temperature was 737.80°C, where the hydroxyl group of mechanical and chemical combined water of clay, burning and oxidation of organic matter from 294.72°C to 408.56°C and then the minerals changes were signi cantly increased due to decomposition of carbonate into CaO and Co2, organic residues and chlorides from 479.89 737.80°C (Fig. 14) [36] .

Treatment and maintenance
The study of the various examinations and analyzes to our studied pottery artifacts from tell El-Shobak in Qalyubia, Egypt proved presence of soil sediments, as well as chloride, sulfate salts, and soot. Pottery objects suffer from breaking and loss of some parts of body Pottery pieces characterized by weakness and lack of durability. According to damage conditions, results of examinations and analyzes and scienti c studies in this eld. Restoration, treatment and maintenance processes applied on our studied pottery artifacts.

Recording and Documentation
The pottery objects (the vessel and plate) excavated from tell El-Shobak in Qalyubia, Egypt were photographed as shown in (Fig. 16a,b) to determine damage aspects or deterioration state before treatment..

Cleaning
The pottery pieces cleaned of soil deposits mechanically using various brushes. The sediments that were highly adherent to the surface were cleaned using metal scalpels. The cleaning method was carried out from top to bottom not to scratch the pottery body [37]. It has given positive results, as shown ( Fig. 17a-f ).
Chemical cleaning carried out in order to clean the various soil deposits using organic solvents. A mixture of acetone and toluene in a ratio of 1:2 respectively was prepared; chemical cleaning for our studied objects done locally for each piece separately according to [38]. Soot sediments was removed using hydrogen peroxide 20 % [39], the calcareous sediments were cleaned using EDTA, that applied as a poultice [40], cleaning results as shown in gure ( Fig. 18a-f )

Removal of Salts
The salts were removed mechanically using brushes and scalpels .cleaning was done under lenses "6X" not to scratch the pottery according to [41]. Then, this was followed by making poultice of distilled water to remove soluble salts such as halite salts, according to [42]. EDTA poultice applied to remove calcareous deposits of carbonates and sulfates salts [43].

Assembling
The initial assembly process for broken pottery started to nd out the places of fracture of pottery sherds according to (Elghareb, 2007) [46].

Filling Gaps
After the assembly process, it was noticed that the pottery artifacts were missing some parts. Replacement was applied using a mixture of microballoon and Pottery powder in a ratio of 2: 1. First, alumina paper applied under the missing part to match the lost part. Second, completion material was prepared, which is a mixture of microballoon and Pottery powder in a ratio of 2: 1. Third, the completion material applied according to (Saleh et al. 2020) [48]. After an hour, it was shaped and polished using various molding tools. Thus, the pottery pieces restored the artistic and archaeological form that it was before burial in the soil. Results shown in (Fig. 20a, c).
After replacement of our studied objects, the pottery artifacts were strengthened, protected and isolated using Paralloid B 82 (3%) by brushing. Pottery artifacts were ready to museum display (Fig. 21a, b).

Conclusion
The research has reached a set of results of great importance in identifying the archaeometric features at tell El-Shobak in Qalyubia. Clay was Nile clay. The additives were sand, grog, and limestone powder. Shape technique used in manufacture of pottery pieces is potter-forming technique. Surface treatment is of slip layer. Burning atmosphere was an oxidizing atmosphere. Research paper also proved that most of the pottery monuments from tell el-Shobak in Qalyubia suffer from damage aspects such as soil deposits, stains, fracture and loss of some parts, Salts crystallization " chlorides, sulfates, carbonates", and weakness and lack of durability of pottery pieces. The research found using of a mixture of acetone and toluene at a ratio of 2:1, respectively to remove clay soil deposits. Using of hydrogen peroxide 20% to remove soot. EDTA used to clean lime deposits. Nano-silica at a concentration of 1% in strengthening archaeological pottery by spraying method. Using a mixture of microballoon and pottery powder at a ratio of 2:1, respectively, to complete the pottery objects. It is preferable to display the pottery artifacts in the museum at a temperature of 20°C and a relative humidity of 55:60percentage.

Declarations
Acknowledgment I would like to extend my sincere thanks and appreciation to Dr. Sameh Al-Tayer, Faculty of Science, Cairo University for his efforts in examination and analysis of our pottery samples. I also extend my thanks and gratitude to the restoration specialists and antiquities inspectors in Qalyubia, my special thanks and gratitude to Mr. Mohamed Hussein, conservator in grand Egyptian museum for his efforts and help.
Declaration of Competing Interest: I disclose that I have no any nancial and personal relationships with other people or organizations that could inappropriately in uence my work reported in this paper, No con ict of interest exits in the submission of this manuscript. Figure 1 represents the pottery objects, Tell Al-Shobak, Qalyubia, A: pottery vessel, B: plate SEM photomicrograph of the rst pottery sample, a: cracking, quartz grains, peeling, salts, and fracture, b : cracking, gaps and crystallization of salts, accidently quartz grains represents XRD pattern of the rst pottery sample tell Al-Shobak, Egypt Figure 12 represents XRD pattern of the second pottery sample, tell Al-Shobak Figure 13 represents XRD pattern of soil sample, tell Al-Shobak, Egypt

Figures
Page 24/28 Figure 14 DTA pattern of the rst pottery sample, tell elshobk, Egypt Figure 15 DTA pattern of the second pottery sample, tell elshobak, Egypt Figure 16 represents pottery artifacts "Case Studies" a: the rst object, b: the second object Figure 17 represents cleaning of pottery artifacts, a: before cleaning, b: during cleaning, c: after mechanical cleaning of the rst object, d: the second object before cleaning, e: during cleaning, f: after mechanical cleaning Figure 18 represents cleaning of pottery artifacts a: before cleaning, b: during cleaning, c: after chemical cleaning of the rst object, d: the second object before cleaning, e: during cleaning, f: after chemical cleaning Figure 19 represents the rst pottery object, a: before assembly, b: during assembly, c: after assembly Figure 20 represents the completion of pottery plate, a : Before completion, b: After applying the reinforcing material (aluminum paper), c: After completing the second pottery object