Abstract
Glaze is not a new material and human beings have been familiar with it for many years. Glazes contain a wide range of organic and inorganic compounds. This research is about identifying the glazes of Achaemenid glazed bricks in Persepolis. So far, studies have been conducted on these bricks in the field of introduction, but comprehensive technical studies have not been done on identifying the composition of their glazes. The glazes used in Persepolis clay bricks are painted in white, light green, light green, dark brown, gray and fawn yellow. In this study, light green, light green and yellow fawn glazes were investigated. This research, which is of experimental-laboratory type with reference to valid scientific documents, has been carried out with the aim of identifying the constituent elements of glazes in Achaemenid glazed bricks in Persepolis. What are these bricks? In this regard, using XRD, SEM, DTA and TGA methods and more chemical analysis of the body and glazes, it was identified that the body of this type of brick is a siliceous body and very porous. According to the experiments, the results obtained in this study show that iron and magnesium are present in the composition of all glazes, which may have been present in the main composition (base glaze) in addition to color effects as impurities.
Keywords: Takhtejamshid, Glazed Bricks, Chemical Methods, Green Glaze, Yellow Glaze, Lead Glaze.

Introduction
Persepolis is undoubtedly one of the most magnificent monuments of the ancient world. Glazed bricks were found by Schmidt in various parts of the building, some of which are in the Museum of Ancient Iran and some in other museums, including the Persepolis Museum. The examples studied in this study are located in the eastern wall of the Women’s Palace during the reign of Xerxes, which is now used as the administrative building of Marvdasht Cultural Heritage. The glazed bricks discussed in this study include the parts of the eastern wall of the palace where the glazing of the bricks of these parts is siliceous. Are examined and the necessity of conducting this research is the repair and protection of these glazed bricks. In the present research, the following questions have been answered: 1- What are the components and main coloring factors in light green, light green and fawn yellow glazes in these glazed bricks? 2- What are the components of the body in these glazed bricks? There are different methods for identifying materials. In this study, because most of the colors have been identified, more attempts have been made to use the methods used to identify and analyze the composition of materials, because this study aims to identify the constituent elements of glazes in Achaemenid glazed bricks. In Persepolis and is of experimental-laboratory type with reference to valid scientific documents and conducting library studies and visiting the historical site of Persepolis, which in this regard were identified using XRD, SEM, DTA, TGA body and glaze methods and the most important The coloring agents of these glazes were identified.

Introducing Examples
The samples were very small that after sampling were in the form of flakes and to prepare the test in powder form. Tests performed on samples Immersion tests were performed on two small pieces of body: sample volume, bulk density and volume weight. In addition, more chemical analysis was performed on the samples, which in total showed that about 79% of Sio2 (silica) and 16% of Ca2o3 (calcium oxide) in the body. On the body sample, XRD test, DTA test (thermal analysis) and TGA test (weight change) were also performed. 

Green Dye Oxides
 A mixture of copper oxide and lead glaze, compared to the chemical composition of the glaze, can produce a variety of green colors. The sample (bold green) was first subjected to XRD test. Also, light green color was tested by XRD and SEM and the results were obtained. In bright green, it shows the presence of two phases of quartz Sio2 and “hydin bergite” Ca (Fe, Mn) Si2o6 In fact, the main phase of both light green and light green is the same, and the percentage of colorants in the composition is probably different. Green The presence or absence of another element can reduce or increase the color of green. Studies show that copper causes blue in alkaline glazes and green in lead glazes. 

Yellow Glaze Dye Oxides 
In lead-rich acid glazes, the addition of a very small amount of chromium oxide, up to 1% at low temperatures, results in a yellow color. The combination with Cao and Sno2 can also give a pink color. Also, Tio2 titanium oxide makes lead glazes yellow and lead-free glazes white. 
The yellow glaze was subjected to XRD test and also SEM test was performed on the above sample. The results show that the yellow color consists of two phases, one CdPbo3 and one quartz phase with a low crystallization percentage. The presence of Pb (lead) is a clear reason for the yellow lead of the glaze, which is one of the main reasons for the greater transparency of the yellow glaze than other glazes. Titanium oxide makes lead glazes yellow, and here we have a lead glaze containing titanium oxide. Therefore, titanium oxide can be mentioned as a possible yellowing agent in this glaze.

Conclusion 
The body of the glazed bricks in Persepolis, which has been studied in this study, looks very porous and is milky in color and shiny like flint. The results of the samples are analyzed and the following points can be stated: XRD test on these bricks confirmed that the body was siliceous, and according to the TGA test, it can be said that calcium carbonate was converted to calcium oxide, and weight loss was also the result of this conversion. The green and yellow glazes were lead. The reason for the gloss of these glazes compared to other glazes is that they are lead, and their transparency is still clear. All glazes contained iron and magnesium, which may have been impurities in the main composition of the base glaze, apart from its color effects. XRD test on green glazes shows the presence of two phases Sio2 and Ca (Fe, Mn) Si2o6. The coloring agent in this glaze is Cu, which is almost more noticeable than other elements (except Si and Ca). Therefore, due to the lead content of the glaze, the presence of copper in this lead glaze causes a green color. The presence of Ca in green glazes causes the color of the glaze to become opaque, and it can be said that one of the reasons for being bright or light is the difference in the percentage of Cao. SEM test of yellow glaze detected the presence of Pb elements from Pbo, K from Kcl, Cr from Cr2o3, Ca from Cao Fe from Fe2o3, Al from Al2o3 and Ti from Tio2. The presence of Pb is one of the main reasons why this glaze is more transparent and lead-free than other glazes, and in lead-rich acid glazes, adding a very small amount of Cr2o3 up to one percent at low temperatures, turns yellow. Titanium oxide also makes lead glazes yellow, so titanium oxide can be mentioned as a possible yellowing agent in this glaze, and the presence of iron has made this color tend to be fawn.

Abstract
Wall paintings drawn in the past depict valuable aspects of history and culture of the time of their creation. The goal of this paper is to explore the concept and readability in the wall paintings of Chehel Sotoun Palace in Isfahan. To what extent the approaches of traditional artists and conservators have been based upon Iranian cultural and artistic heritage. how can the meaning behind Chehel Sotoun’s paintings’ readability be evaluated? The research method used in this paper is descriptive-analytical. The goal is to examine the thoughts and theories of conservation and preservation scholars in regards to the influence of Iranian-Islamic cultural background on traditional conservation and preservation approaches in these works. It also explores the perception and significance of the main readability element during the mentioned conservation period. The analyses conducted indicate that approaches of traditional conservators and artists were based on attention to the history and art of the Iranian culture and artistic styles of their own time. Relying on emulation and reinterpretation of paintings and emphasizing on passing on the content and inner meaning of the work through the preservation of the narrative form of mural paintings in Chehel Sotoun, they have provided greater readability of these works for the audience.
Keywords: Protection, Conservation, Readability, Mural, Chehel Sotoun.

Introduction
Establishing a proper connection between the audience and artworks will not be possible unless we understand and grasp the inner meaning. The principle of readability is always based on the relationship between the creator, the art, and the audience. Mural painting have been a symbol of human enthusiasm for creating artworks. Starting from simple forms that symbolize celebration and hunting, Mural Paintings have transformed into concepts that represent the culture and national symbols of a nation or a group of people. The passage of time leads to physical damages to an artwork. When it comes to wall paintings, the conservator must make sure to adhere to scientific principles and important conservation considerations such as aesthetics, authenticity, integrity, and readability. To respect the integrity of an artwork is an essential part of artistic authenticity and will contribute to the readability of the artwork (Great, 2006, p. 6, Pollsson).
In Iran, we still observe that the restoration of historical artefacts are done based on personal views. Salvador Muñoz Viñas argues that classical conservation seeks the objective truth of an artwork and the purpose of conservation is to reinforce its structural and cognitive integrity in order to preserve its true nature. Artworks contain a wealth of information, messages, and meanings. The role of the conservator should be performed properly to enhance the readability of the artwork.
Readability has a hierarchical structure that ensures the preservation of the authenticity and cultural values of an artistic work. Understanding the various dimensions of communication between the creator of the work and the contemporary and future observer and audience has received considerable attention from conservation scholars. The audience, depending on different political, social, and cultural and personal views, can have different perceptions of the work. Conservation and preservation operations also have a significant impact on the readability of artistic works in order to understand and interpret the inner truth of the work.
Objective: 1- This study aims to explore the approaches and methods of traditional preservation and conservation in the wall paintings of Chehel Sotoun Palace in Isfahan, Iran. It aims to analyse the cultural and artistic history of Iran reflected in these paintings and to elucidate the concept and significance of readability in these artworks during the conservation process.
Question: The question is to what extent Iranian cultural and artistic history has been considered by the traditional artists and conservators. With regard to the wall paintings, the question asks how the concept of readability could be evaluated.
Hypothesis: Readability, as a principle in the preservation and conservation of historical-cultural artifacts, especially wall paintings, can depend on the theoretical and practical conservation approaches of its historical period.
Method: Following research is conducted using a descriptive-analytical method with a qualitative and interpretive approach. Data is collected through document studies, library research, observations, and fieldwork to analyze the relevant topics regarding the significance of readability in the approaches of preservation and conservation of the said wall paintings.

Discussion
This research examines the significance of readability in the preservation and restoration of the wall paintings in the Chehel Sotoun Palace in Isfahan, Iran. The findings reveal that the techniques employed by past artists and restorers are deeply intertwined with Iran’s cultural and artistic heritage, prompting critical questions about how these methods affect the artworks’ overall readability.
The study indicates that aesthetic considerations often take precedence over traditional restoration practices, resulting in a neglect of the intrinsic value and historical context that enhance a work’s readability. This emphasis on aesthetics can lead to misunderstandings regarding the artists’ intentions and the cultural narratives embedded in the wall paintings. While restorers aim to preserve the quality and visual appeal of the artworks, their methods may inadvertently result in a loss of originality and meaning, thereby undermining the effectiveness of the narratives intended for modern audiences.
Moreover, the paper identifies a significant gap in existing research concerning the evaluation of readability after restoration. Although many studies focus on the technical aspects of restoration, few address how these interventions impact the viewer’s ability to understand, interpret, and engage with the artworks. This gap highlights the necessity for a paradigm shift in restoration practices, prioritizing readability rather than treating it as an afterthought. It is important to acknowledge the limitations of this study; the findings are specific to the wall paintings examined and may not generalize to all restoration practices. The cultural nuances and historical significance of artworks vary greatly across different regions and periods. Additionally, the subjective nature of readability complicates the creation of a standardized framework for assessing the effectiveness of restoration methods.
Based on these findings, future research should focus on developing a comprehensive methodology for evaluating readability in restored artworks. This could involve interdisciplinary collaborations among restorers, conservators, art historians, and audience researchers to better understand the impact of restoration practices on viewer experiences. Incorporating audience feedback into the restoration process could enhance readability and engagement, preserving both the aesthetic and narrative dimensions of the artworks for future audiences.
Ultimately, this research emphasizes the importance of integrating cultural heritage, artistic intent, and audience engagement in restoration methods. By doing so, it fosters a deeper appreciation of the historical narratives within artworks and the artists’ visions, ensuring their continued relevance and readability for contemporary and future audiences. This approach honors the original creators while illuminating the cultural roots of our shared heritage.

Conclusion
Previous artists and conservators made interventions in their preservation and conservation approaches to the wall paintings of Chehel Sotoun Palace in Isfahan, taking the Iranian cultural and artistic history as well as methods and techniques of their predecessors into account. These interventions are considered significant due to their consideration of the historical period, cultural-artistic perspective, style, and techniques of that era. This phenomenon also existed in European countries, where skilled painters would perform conservation work on their own or on the works of others, thereby leaving their artistic presence on the intended artwork. They aimed to keep the inner content of the work alive as well as reinterpret and transfer that content to their own era, providing a platform for the audience to receive the narrative and inner content of the work. The longevity of the narrative in the mind and memory of the audience leads to the readability of the work. This kind of understanding is what makes the art readable.
If the traditional approaches to the protection and conservation of wall paintings in their own era and time are evaluated, not only the perspective and method that is considered as part of their valuable traditional heritage and historical-cultural values will not be condemned, but it will be contemplated and protected more than ever. Looking at traditional conservation will not only face criticism but will also have the potential and value to envision a better future for the preservation and conservation of historical-cultural works in Iran.