A Comparative Study of the Implementation Technique of the Koshtehbori Stucco Decorations of Ali Qapu Palace and Pirnia House in Nayin

Introduction: During the Safavid period, innovations were introduced in stucco decoration. The Koshtehbori stucco decoration is one of the most attractive and unique architectural decorations of the Safavid period, which was implemented with various motifs in some of the buildings of that period, and represents a special creativity and innovation that is different from the implementation of other types of stucco decoration. Knowing the methods and implementation steps of stucco decoration in restoration projects and studying them is considered one of the essential elements and an inseparable part of the protection of historical stucco decorations. The Safavid-era Koshtehbori stucco decoration, with different techniques and Khatai, arabesque, animal, human, or inscription motifs, was prepared and made on a fine coat of plaster mortar, and based on the remains, the most frequently used stucco decoration belongs to this era. The Koshtehbori stucco decoration with different execution techniques from other traditional plastering methods, in which the design or some motifs were executed with an angle of 90 degrees and with an average depth of less than one millimeter, was carved and polished with a plastering tool, and then the remaining flat surfaces were painted in the manner of murals, but in some buildings, such as the Pirnia House, small sections of the surfaces were painted. Most of the decorations of Ali Qapu Palace include stucco decorations known as Koshtehbori. Koshtehbori stucco decorations in Ali Qapu Palace are in the form of paintings of flowers and plants, foliage and shapes of birds and animals, which are located in various parts of the palace, such as rooms, ceilings, corridors and stairs. The stucco decoration known as Koshtehbori is located in the house of Pirnia in the three spaces of Sofeh (south Iwan), the chair room and the upper room.
Purposes & Questions: The purpose of this research is to identify the similarities and differences, the diversity of the method, and the implementation of stucco decorations of the Ali Qapu Palace of Isfahan and the Pirnia House in Nayin. The questions of this research are: 1.What is the technique of implementing the stucco decoration of Koshtehbori based on the designs in Ali Qapu Palace and Pirnia House? 2.What are the similarities and differences between the execution of the Koshtehbori stucco decorations of the Ali Qapu Palace in Isfahan and the Pirnia House in Nayin?
Methods: The research method is descriptive-analytical and comparative, and the findings were collected through Koshtehbori studies and field observations.
Findings & Results: The results of the studies showed that the execution technique of Koshtehbori is divided into seven types based on the type of designs in both historical buildings. Stucco decoration in both buildings, including the implementation of brick support, clay straw lining, a layer of plaster with a smooth and polished surface, a layer of preparatory canvas, transfer and line design, and in most of the Koshtehbori stucco decorations on the elevation, the motifs are similar to the carved background of less than one millimeter. This stucco decoration in Ali Qapu is used for painting the motifs with penciling or Labshor around the details of the motifs, as well as in some designs around the frames without carving in the form of painting and combining Layechini and Koshtehbori, using a single Layechini frame, or painting the carved background in some frames such as medallions. It is different from the Pirnia House. Contrary to the Ali Qapu Palace, in the Pirnia House, the majority of the surfaces of designs and motifs are unpainted, and only a few parts of the motifs are painted. This coloring can be seen in a few parts of the surfaces of the motifs, using green, dark brown, light and red colors, applied to the back edges of the lining of the domes, some animals and plants in a scattered form and some lines around frames and borders. In the Pirnia House, the absence of color in most of the motifs and the initial outlining of the details of the motifs – reminiscent of pen drawing – as well as carving the centers of round flowers and the mirrors of Shah Abbasi flowers, or carving inside the details of Shah Abbasi flowers and motifs, and arabesque bands with a depth of five mm, are different from those in Ali Qapu Palace. The Koshtehbori stucco decorations of both buildings are similar in the use of Khatai and arabesque motifs, trees, animals, and birds. However, in Pirnia House, human motifs are used in some of the frames, and inscriptions in Nastaliq script appear on the walls beneath the motifs in the Sofeh Iwan, the house's seat room, and the upper room.