Abstract
Among the architectural arrays of Imamzadeh Hossein in Qazvin that can provide valuable information to researchers, are the remaining parts of the murals. Considering that Qazvin was the capital during the second period of Safavid rule, the study of Safavid and Qajar period buildings in this city can be of great importance. Compared to the existing historical monuments, few studies have been done on the technical knowledge of the layers of historical murals.In the present study, the identification and recognition of pigments related to the remaining murals of this monument and gilded layers has been considered. Also, in order to complete the technical information of the murals, the mortar of the fine coat (finishing plaster) and scratch coat (levelling coat) under the paint has been studied in terms of structure and chemical composition. To identify the pigments used in the murals as well as the materials used in the mortar of the underlying layers of the mural and the floor mortar, the hydraulic properties and the mineral and chemical composition of the mortar from X-ray diffraction, scanning electron microscopy coupled with energy dispersive spectroscopy and digital microscope have been used. As a result of the studies, it was found that the Pastiglia in the murals is made of a mixture of gypsum and Bole (Armenian Bole, Hormoz Bole). Apply a white Primary layer on the pastiglia on which the gold leaf is applied with low copper impurity. In this murals, three types of gold sheets have been executed. Green: A mixture of arsenic pigment with azure blue and Prussian blue; Green-blue: a mixture of green earth pigment (Celadonite) with white lithopone; Blue: a mixture of azure and Prussian blue pigments with White lead; Red: A mixture of ocher red and orange arsenic; Primary layer filler: a mixture of Huntite and White lead; black: It is a mixture of cobalt black and iron black. The structure and composition of mortars were also identified.
Keywords: Mural, Pigment, Gilding, Structural Study, Mortar, Qazvin.

Introduction
The technical diversity of murals in the Safavid and Qajar periods is one of the important issues of knowing historical murals. To technical understanding historical mural, its different layers are subjected to careful scientific study. The main layer is the color layer which consists of two parts: dye and binder. It should be noted that the array of gilding in the mural and the borders of the mural is also considered as a mural. Imamzadeh Hossein is one of the prominent buildings of Qazvin city. Most of the murals of this building belong to the Qajar period. Evidence shows that traces of the Safavid periodare also left in this building in the lower layers.
The aim of the current research is to obtain technical information about the layers of murals of this historical building. Identifying and recognizing the pigments in historical murals from archeology point of view helps completing the technical information about the use of pigments by artists. Some pigments have a specific starting date, which helps clarify the date of making the murals.
In archeology, studies have been conducted regarding the technical knowledge of different layers of historical murals in Iran, but very few studies have been done considering the volume of murals in Iran in different periods. Therefore, it is necessary to more complete these studies over time which its result is to complete the database in this field. In the upcoming research, in order to know more about the murals, technological studies were done on it. After field studies, the pigments used in the murals were sampled and identified. To complete the information, the lining layers and the substrate and a sample of the floor mortar were also studied. In this regard, the main questions of the current research are: What pigments are used in the murals of Imamzadeh Hossein in Qazvin? What method was used for gilding in these murals? What are the physical and structural characteristics of the lining layers and substrate of the studied murals?

Discussion in the Results and Findings
a. Scanning Electron Microscope: In the sample (2021.Q.IH.1) there is a large accumulation of gypsum crystals and intertwining has been created between them. The empty space between the crystals is little and also the crystals are irregularly placed together at different angles. In 2021.Q.IH.10 sample, needle- shaped gypsum crystals that are intertwined can be seen in many parts. In 2021.Q.IH.11 sample, gypsum crystals in different sizes are placed at different angles. In this sample, there is no long needle crystal and instead, the crystals have grown a lot in the width direction. In 2021.Q.IH.12 sample, the gypsum crystals are slightly different in terms of shape from the samples of the floor and lining layer.
b. Energy-dispersive X-ray spectroscopy (EDX): In 2021.Q.IH.1 sample, there is a small amount of silicon, aluminum and magnesium, which is related to soil. In 2021.Q.IH.2 sample, the amount of sulfur is about 13% which some part of it is related to yellow pigment and some part is related to blue pigment. In 2021.Q.IH.3 sample, elements of potassium, aluminum, iron, magnesium and silicon can be seen next to oxygen. These elements are related to Verona green or green earth pigment. In 2021.Q.IH.5 sample, a high percentage of gold and a relatively low percentage of copper were detected in the sample. In 2021.Q.IH.6 sample, two coloring elements, iron and arsenic, along with sulfur have been detected. In 2021.Q.IH.7 sample, the main filling material is huntite or chalk. On the other hand, a small amount of lead has been detected in this sample. Gold, copper and iron have been detected in 2021.Q.IH.8 sample. In 2021.Q.IH.9 sample, two elements, cobalt and iron, along with sulfur, are significant and influential elements in making black color. In 2021.Q.IH.10 sample, the highest percentage of elements is related to calcium and sulfur. In 2021.Q.IH.11 sample, except the main elements of gypsum, a very small amount of elements of silicon, aluminum and magnesium have also been detected.
c. X-ray diffraction spectroscopy: As a result of the phase analysis of 2021.Q.IH.1 sample which is related to the lay-up under the gold sheet, quartz has been detected. The quartz detected in the lay-up is related to the red flower (Armenian flower) that was added to the plaster during the mortar processing. The next identified phase is gypsum. As a result of the phase analysis of 2021.Q.IH.10 sample which is related to the floor coating mortar, quartz has been detected. The next identified phase is gypsum. As a result of the phase analysis of 2021.Q.IH.11 sample, which is related to the floor coating mortar, anhydrite phase has been detected in the studied sample. The amount of anhydrite in the lining layer is higher than gypsum. As a result of phase analysis of 2021.Q.IH.12 sample, which is related to the substrate layer in the studied mural, quartz has been detected. The granularity of the quartz phase in the substrate was much finer than the previous samples. The next identified phase is gypsum.

Conclusion
The lay-up used in the murals of this building is made of a mixture of plaster and red flower (Armenian flower, Hormoz flower). Green color is a mixture of arsenic pigment with lapis lazuli and Prussian blue. Blue-green color is a mixture of green earth pigment with lithopone white. The blue color is a mixture of lapis lazuli and Prussian blue pigment along with white lead. The golden color of embossing is gold sheet with a small amount of copper impurity. The layer that is applied on the lay-up is also a gold sheet with a small impurity of copper. In line with the studies on the shiny brown sample, it was concluded that this layer is a gold sheet with copper and iron impurities, which its surface has corroded and darkened over time. In fact, three types of gold sheets have been used in the studied murals that two of them are similar and seem to belong to the same period. A layer that is different in terms of the composition of elements and impurities belongs to later periods. The red color in these murals is a mixture of red ocher and orange arsenic. The white color filling the preparatory layer is a mixture of huntite and white lead. Black color of embossing is a mixture of cobalt black and iron black. Contrary to imagination, the floor mortar is a gypsum mortar with two phases of gypsum and anhydrite to which some sand and soil have been added. Due to proper processing, this mortar has adequate strength, although humidity has caused damage to the work over time. The lining layer and the substrate in the studied murals are made of plaster mortar. There is a difference that the thickness of the lining layer is greater than that of the substrate and it has coarser graining and more impurity. On the other hand, the looser mortar of the substrate is due to the way of processing, and the arrangement of gypsum crystals is different from that of the lining layer.