Conservation and Restoration of a Sample of Human Skeletons Belonging to the Iron Age Museum of Tabriz

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Esmailnezhad Jalil; Majidi Fariba; Yazdani Gholamreza; Razani Mehdi

Title

Conservation and Restoration of a Sample of Human Skeletons Belonging to the Iron Age Museum of Tabriz

Author(s)

Esmailnezhad Jalil | Majidi Fariba | Yazdani Gholamreza | Razani Mehdi | Issue Writer Certificate

Keywords

Keywords: Iron Age MuseumQ4

TabrizQ4

RestorationQ4

BonesQ4

Human SkeletonsQ4

Nano HydroxyapatiteQ4

Abstract

Abstract Bones and human skeletal remains are among the most important materials found in many archeological excavations. Bones are composite materials consisting of organic and inorganic parts. Minerals constitute 70% of the dry weight of Bones and organic substances the rest. This valuable material is degraded by environmental factors and microorganisms and its physical and mechanical properties are lost. Therefore, it is necessary to preserve Bones. The Iron Age Cemetery of Tabriz with its buried human remains and the items found inside the tombs in the natural environment has been converted into a museum site. This paper describes the preservation and reconstruction of a sample of human skeleton belonging to this museum site taking into account the available pictures related to the excavation and removal of the factors damaging the skeletons. The results of the tests on soil EC, type of soil granulation and pH, the qualitative identification of the dissolved salts (anions), and the determination of the moisture content in the burial site indicated that the soil had a high moisture content, strong saline salts, and a loamy texture. The soil and skeleton had neutral (weakly alkaline) pH values. After carrying out the necessary studies, the skeleton was transferred to the workshop to be preserved and reconstructed and the soil in the bottom of the tomb was removed and desalinated with distilled water. Nano Hydroxyapatite was used to improve the strength of the Bones and Moldano and Simacryl R83 to reconstruct the lost parts of the skeleton. Plexiglas was employed as the insulator in the bottom of the tombs to cope with the rising moisture content. Samples and MethodsSamples:The skeleton under study was obtained from the excavations in 2003 at the Iron Age cemetery (Blue Mosque Site) under the supervision of Alireza Hojabri Nobari. Currently, it is on display at the Iron Age Museum. This skeleton, identified as number 82/51, was discovered during the fifth season, in Workshop 3 and Trench A.Laboratory Methods:To identify the compounds present in the burial environment and the soluble salts within the Bones, sampling was conducted on the bone and the surrounding soil. Initially, the collected samples were air-dried to remove the free water present in the soil tissue and then divided into two portions. The first portion was used for particle size analysis. The second portion was utilized for qualitative identification of the soluble salts (anions), pH measurement, and determination of water content and organic matter. Additionally, the identification of soluble salts and pH measurements were performed on the bone samples.Soil Particle Size Analysis:Particle size analysis plays a crucial role in determining the water-holding capacity of soil and is also one of the conventional methods for identifying soil types. To this end, the soil particle size identification method using the hydrometer method based on ASTM D422-63 standard, available at Kimia Gostaran Novin Azmaye Tabriz Soil Laboratory, was employed. The results of this analysis indicated that the burial soil is classified as loam clay soil.Soil Organic Matter (SOM) Test:To measure the amount of water and organic matter present in a soil sample, the tested sample measured the percentage of water and organic matter. The water content in the burial soil is 10.5%, and the organic matter content in the soil is 3.9%.Moisture Measurement:To measure the moisture inside the burial and environmental moisture, a digital moisture meter TFA 44.1004 was used, which was available at the Iron Age Museum. The average moisture inside the burial and environmental moisture in July 2019 was 87% and 25%, respectively.Temperature Measurement:The temperature inside the burial was measured using a mercury thermometer with minimum and maximum temperature readings in degrees Celsius. The average maximum and minimum temperatures in July 2019 were 21°C and 10°C, respectively.pH Measurement:To measure the pH of the soil and bone samples, the Metrohm pH 827 pH meter model from Switzerland and litmus paper at the Islamic Art University of Tabriz were used, following the ASTM D4972-01 standard.Soil pH is influenced by various factors such as the presence of soluble salts and their type and composition, and it plays an important role in soil processes and chemical reactions. Soil pH indicates the physicochemical environment of the soil in an area. According to the conducted experiment, the pH of the soil was determined to be 5.7 using litmus paper and 7.7 using the pH meter, while the pH of the bone was determined to be 5.7 using litmus paper and 3.7 using the pH meter. Based on the test results, the pH of the soil and burial bone samples can be classified as weakly alkaline with a value of 8.2.Soil Electrical Conductivity (EC):Soil electrical conductivity can indicate the level of salinity and soil fertility and can determine the presence of soluble salts. The result of soil electrical conductivity for the burial indicates 12.17 ds/m. The obtained result indicates that the soil sample had a high electrical conductivity, indicating the salinity of the soil.Qualitative Identification of Soluble Salts:To identify soluble salts in the soil and bone, 5 gr of each sample was taken, powdered, and dissolved in 20 ml of distilled water and heated. The solution containing the sample was placed in a centrifuge to separate the sediment from the solution. The sediment was tested for the presence of carbonate ions (CO32-), and the solution was used to identify chloride ions (Cl-), nitrate ions (NO3-), phosphate ions (PO43-), and sulfate ions (SO42-).Conservation and Preservation Measures:The following conservation and preservation measures were carried out for the implementation of this archaeological and conservation research article:1. Documentation and extraction of the human skeleton from the burial site and its transfer to the conservation and preservation workshop at the Iron Age Museum in Tabriz.2. Soil desalination at the burial location.3. Consolidation of the grave walls.4. Cleaning the Bones of the human skeleton.5. Desalination of the Bones.6. Consolidation of the Bones of the human skeleton.7. Fragmentation and reassembly of the Bones.8. Restoration and color matching according to conservation theoretical principles and foundations.9. Design and implementation of a moisture barrier using Plexiglas and its placement inside the burial site.10. Reburial of the remains and arrangement according to the archaeological excavation images. Conclusion:According to the conducted experiments, it has been established that high relative humidity and the presence of salts are detrimental factors for human skeletal remains. The high humidity causes salts to enter the pores and cavities of the Bones, leading to the dissolution of mineral components and an increase in bone porosity. Consequently, when the humidity decreases and the Bones dry out, the salts crystallize and exert mechanical pressure, resulting in surface cracks. To address this issue, a desalination process was performed on both the Bones and the soil in the grave. Additionally, a moisture barrier made of Plexiglas was utilized to prevent moisture-related damage. Nano-hydroxyapatite, a substance consisting of calcium and phosphate compounds that closely resemble the inorganic part of bone, was employed to enhance the structural integrity of the Bones. This substance forms a chemical and structural bond with the inorganic components of the bone, facilitating desirable adhesion.

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Scientific Information Database

ISSN: 2588-4824

Journal Paper

Conservation and Restoration of a Sample of Human Skeletons Belonging to the Iron Age Museum of Tabriz