Abstract
The two most prominent types of material cultures in eastern Zagros are Bronze Age black burnished pottery (3rd millennium BC) and grey Iron Age pottery (second and first millennium BC) that were dog out during archaeological expeditions are being investigated and reconstructed. The technique of firing these two types of pottery will be analyzed in the present study. The main objective of this research was to reconstruct the similar conditions and techniques of these two pottery class using experimental archaeological methods and practical reconstruction of traditional kilns. Along this route, the technical similarities and differences are discussed, relying on archaeological data and comparing it with reconstructed samples. In this regard, two samples of each of the Bronze Age and Iron Age potteries were reconstructed and samples were produced and refurbished by traditional kiln that utilize modern laboratory facilities and precise temperature-measuring devices and are heated in the firing process. The results of the try and error tests indicated that baking with chemical reduction and emergence of gray color is the most important common feature of difference of gray pottery with other pottery assemblages. The firing technique and the structure of the kilns are the most important factors in distinguishing the two types of bronze age and iron age pottery assemblages. What is certain is that with the evolution of the furnace structure, the heat generated from about 700 ° C in the gray Yanniq period of the Bronze Age has increased to about 1000 ° C in the Iron Age specimens, resulting in a higher firing quality as well as a complete and complete chemical reduction of the vessels. Practical comparison of the reconstructed samples showed complete conformity of their characteristics with the ancient specimens (Pisa Tepe, Tushmalan Tepe and Ahmadabad Tepe) and also revealed the secret of producing these two species of gray pottery.
Keywords: Eastern Zagros Central Regions, Bronze Age Pottery, Iron Age Gray Pottery, Experimental Archeology, Kiln, Firing and Reduction.

Introduction
In modern archeology, the scientific question is not what we know, but how we know it. This point of view is one of the most important and at the same time the simplest modern archeological approach to past phenomena (Alizadeh, 2004: 91). Therefore, the idea of reconstructing the conditions and the environment in analogy with what was reported in the reports and data was presented. In response to such ambiguities, it can be said that using more modern methods in research such as “experimental archeology” will increase the accuracy of the premises. Early sections of this study have followed up on existing data and library studies of past sources and reports; therefore, in the next section, reconstructing the conditions and environment consistent with the information provided, has been the author’s main goal. In this section, the “kiln making” and the experience of firing the pottery in these kilns were practically achieved, leading to new information on the evolution of the gray pottery production; Proved the assumptions to be true, so that by producing products that were quite similar to ancient data, the key role of the resuscitation process in the firing process and the important role of kiln design and structure in the specific type of firing were demonstrated However, in some sources (Majidzadeh, 1370: 9-7), general references to the reasons for the pottery being grayed out as interfering with elements such as oxygen, iron, and carbon, and in other research, the reduction process was the main reason ( Kambakhshfard, 2010: 296). Finally, it can be added that according to the comparisons and studies of the samples, the firing of the Iron Age gray pottery somehow evolved into conscious firing methods during the first millennium BC. Although in the early Bronze Age achieved to somehow the technique of reduction firing, but only in Iron Age pottery assembladges, the correct pottery reduction firing can be clearly seen.

Discussion 
After the pottery kiln reconstruction operation and the success of the production of the specimens, only by a very simple comparison, the accuracy of the existing probabilities, which were the unknowns of the equation, can be easily ascertained; however, accurate and scientific recordings of the work confirmed these results. Based on these empirical findings for the Bronze Age gray pottery, although previous findings indicate that the potter accessed the firing process may be regenerated, it is due to the amount of carbon accumulated in the samples (carbonization) that is due to its proximity to heavy smoke and firewood. It can be said it was still not possible to control precisely the firing conditions by the potters.
According to existing reports and objective observations of the Bronze Age pottery assemblages, such pottery has much thicker bodies than the gray Iron Age pottery, and empirical indications indicate lower firing temperatures; There are some other features that have been ignored because of their relevance to the subject of this study, that is, firing techniques. As for its firing technique, most of the existing documents refer to the possibility of a ditched type kilns, which is not far-fetched from the evidence.
Reconstruction of the firing conditions of the Bronze Age pottery indicated that the kiln was probably a small-size oven shaped hole that provided a relatively primitive chamber for controlling fire and firing in the vicinity of heavy smoke from firewood and fuel. Reconstructed furnace firing sector were able to provide similar conditions for oven-kilns. In this oven shape kiln, pottery was quite similar to the Bronze Age specimens, especially the Yaniqe or Godin IV pottery, but due to physical limitations and initial quality and reduction facilities, they were never comparable to those found in the Iron Age.
In fact, despite efforts to create optimum conditions, these types of kilns are not capable of achieving a higher quality product such as gray ceramics of the Iron Age, even though due to the excessive energy loss of the maximum heat produced in the oven by about 700 Centigrade did not exceed that production of higher quality pottery in these conditions is almost unlikely.
As the kiln construction techniques expands and evolves, the reconstituted kiln will eventually move closer to the plan of the kilns in the Iron Age, and after a complete overhaul, the result also confirms this claim. In this kiln, reasons such as the separation of the firing chamber, the dominance of proper flame allocation to the vessels, the closure of the pipes and the non-collision of the pipes with the air, made it easier to obtain the appropriate chemical reduction conditions.
In fact, the gray color of the potteries reconstituted with the conditions of the Iron Age kilns are mostly due to the correct reduction and dependence of the carbon chemical interactions and the consumption and replacement of the oxygen present in the composite iron oxide in the ceramic body soil. The technical differences in these two species, which are mainly due to differences in the structure of the kiln structure, are evident in the firing quality of the bodies and the difference in the intensity of carbon accumulation and the color difference between the surface and the body depth.

Conclusion 
After examining the documentation available in the time and location of interested research subject, it can be said that the gray pottery has two major variations, both of which have significant differences in terms of time of occurrence, originating culture, and specific production and reduction techniques. In terms of firing technique characteristics, it can be said that the only similarity between these two cultural products is the presence of a “different gray color” in the body of both types of pottery, which has brought them closer together because of the differences in the characteristics of the other species.
The characteristics of the Early Bronze Age gray pottery that distinguishes it from the Iron Age gray pottery lie in the presence of two main factors, namely the type of kilns and the pottery body features. According to the comparison and examination of samples, firing gray pottery assembladges of the Iron Age somehow evolves conscious firing methods and only in the examples of the Iron Age pottery can a complete and correct chemical reduction of a pottery be clearly seen.
In fact, both of these types of potteries are common in creating an atmosphere of chemical reduction in firing, both of which are interesting in their quality and type of performance, which can be attributed to the progressive evolution of the kiln structure and the facilities and knowledge necessary for its construction and observance for centuries.

Abstract
Gray pottery is one of the most significant and important cultural artifacts discovered from the Bronze Age sites in the southeast of the Iranian plateau. This style of pottery has been obtained in a very large amount from the Chagardak Asr-e-Faraghi site of Chah Hashem Plain in Baluchistan, which has so far been far from the views and studies of archeology, archeology and artistic history of the southeast of the Iranian plateau. The main question of this research is about how to make and decorate these pottery. It seems that pottery making was developed in this area and they had different construction methods. The present research has been done by analytical-experimental method and based on laboratory studies. The studied objects belong to the Museum of Southeastern Iran. Measures such as documenting the condition of objects as well as sampling necessary for laboratory tests have been performed at the restoration workshop of the Museum of Southeastern Regions of Zahedan. Then, using thin section petrographic studies (OM) and instrumental analyzes with SEM-EDX and XRD methods, the data are analyzed in order to achieve the research objectives. In this study, 11 samples of gray pottery related to Chegardak area, which were obtained from emergency excavations in 2018, were performed. All pottery was wheeled and gray in dark to light and with different thicknesses but in the range of thin pottery. Archaeological studies on pottery suggest a similar composition, but show that different production methods were used. The pottery in question was pottery produced in high heat furnaces and advanced methods such that precision in construction, elegance and strength were considered by the potters. The results show that pottery in this area has been a very advanced industry that has used iron and manganese-based minerals to decorate the pottery.
Keywords:  Archeology, Petrography, Bronze Age pottery, Chegardak, SEM-EDX, XRD.

Introduction
Southeastern Iran is one of the most important and prominent regions in terms of human evolution in the Bronze Age. Evidence of this is the dispersion and existence of numerous ancient sites and hills related to the third millennium BC in this area. Significant sites such as Burnt City (Tosi, 1976; Biscione et al., 1977; Piperno & Tosi, 1975; Tosi, 1968) ¬, Bumpur (DeCardi, 1968; Mortazavi, 2004; 2006) 2018), Speedge (Heidary et al., 2019), Khorab (Stein, 1937) and Domain (Tosi, 1970) as well as Chegardak area (Heydari et al, 2015) are prominent and prominent examples in Sistan and Balochistan, all of which have been studied and various archaeological studies to date Chagardak Archaeological Site (27 ° 5’14 ‘’ N; 59 ° 7’8 ‘’ E) is located in Delgan city and Dasht-e Chah Hashem village, 10 km northeast of Chagardak village (200 km west of Iranshahr city). This area takes its name from the nearby village, namely Chagardak. This area is located in a flat and low plain. The ancient site of Chagardak in the plain of Chah Hashem Jazmourian includes a hill and two cemeteries related to the Bronze Age of Balochistan. This area has been in turmoil and damaged in 2005 due to extensive destruction and looting by traders. During the salvage excavations carried out in 1397, the Archaeological Department of the General Directorate of Cultural Heritage of Sistan and Baluchestan Province discovered a variety of artifacts, including pottery painted in pea, gray and red. Gray pottery is one of the most important finds from the lesser-known Chagardak site in Balochistan. Therefore, these findings have been analyzed and studied in this pilot study using petrographic, SEM-EDX and XRD methods. In the first stage, petrographic analysis was performed on all pottery. In the study of pottery petrography, a very important issue is the materials added to the pottery paste. All the pottery is wheeled and gray in the range of dark to light and with different thicknesses, but within the fine pottery of this region. Samples were named based on the first letter of the name of the Chagardak site in Latin (CH) and the sample number from 1 to 11. Among these specimens, numbers 1 to 8 are broken and small pieces of pottery obtained in the excavations of this area, and numbers 9 to 11 are pottery that is much more complete and with Ability to perform restoration operations (Table 1). Gray painted pottery is one of the types of pottery that has been obtained in many areas of southeastern Iran. Their designs are taken from the ecology of the region and the culture of the people of that period. Scanning electron microscopy analysis equipped with X-ray fluorescence analysis (SEM-EDX): for microscopic examination of the pottery matrix, identification of minerals as well as melting and vitrification stages of the pottery, as well as identification of the chemical composition of the matrix and minerals. SEM-EDX method was used. The SEM device used is the MIRA3 model made by Tescan, an American product. Also, to identify the composition of pigments used in painting ceramics, the EDX elemental method and the VEGA / TESCAN-XMU model made in the United States, which was coupled to the above SEM machine, have been used. The resolution was 1.5 mm at 15 kV and 4.5 nm at KV1 with BSE detector. Also, the method used in this research is point analysis. The mentioned experiment was performed in Razi Metallurgy Laboratory of Tehran. X-ray diffraction (XRD): X-ray diffraction method has been used to identify crystalline phases and mineralogical studies in the desired pottery. The model of the device used is X’spert Prompd Panytical made in the Netherlands, which has been done in Razi Metallurgical Laboratory of Tehran. The samples were analyzed at 30 Ma current and 40 Kv voltage. Information on the identification of crystal phases based on PDF2 database was reviewed and obtained by Xpert High Score Plus software version 2010. Therefore, how the art of making and recognizing the pottery industry in this region can be one of the most important questions and goals. Therefore, in this research, we have tried to answer some questions such as the following questions by using some common methods of analysis in the archeology of ancient pottery. A) What kind of mineralogical composition does the pottery discovered from Chegardak have? B) Structural and archaeometric studies of ceramics show what kind of process shows in the way of making and baking pottery?

Conclusion
These experiments showed that the pottery has a very dense, hard and non-porous texture, which shows that the prehistoric potters of the Chagardak area five thousand years ago were very precise and skilled in the type of drilling and processing method. So that no emptiness or signs of improper weaving can be found in the pottery. This point should be considered as one of the most important features of gray pottery in this region, especially in the southeast of Iran. On the other hand, the resulting studies show that the soil used in the manufacture and production of pottery paste is very desirable, washed and free of any additives. As their strength is so high after firing that they can not be easily broken, this can be seen well in the type of sintered and semi-glass texture of pottery. Also in XRD phase analysis, the presence of high heat phases was detected. It is very likely that high heat furnaces using regenerative conditions were used in the construction of the pottery. On the other hand, in the archeological excavations and emergency excavations carried out by the archeological group of the area under the supervision of Mohammad Heydari, the architectural remains of a pottery kiln, molten pottery and kiln were discovered, which shows this. This industry has been an art and native production of the people of this area. The last stage of producing a pottery was the methods of polishing and decorating it to produce a magnificent work of art. Elemental studies showed that the prehistoric painter and craftsman of Chagardak used iron-based minerals such as hematite and red recently to record red colors, and a combination of iron-oxide and manganese-based materials to produce black and dark colors.