Āhak (o Sāruj) bori (Art of engraving limestone)

The engraving of images in relief on the surface of the limestone is called Āhak bori. Among the best known examples of Āhak bori, in Iran, we can mention the decorations of the hammams of Casa Āmeri (Kāshān) and of Khān (Sanandaj).
The Sāruj represents an innovation brought to light by Iranian architects in very ancient times. To produce it, they created a mixture of clay and limestone (with a ratio of six parts to four) and, once this hard mud was obtained, they spent two days working it. Later, they added ash from the kilns and the cattail fiber. At this point, using 10 cm thick wooden rods, the fresh mixture was beaten so as to mix everything well.
In past eras, the Sāruj enjoyed considerable importance and was used to build water basins, bridges, Āb anbar (water cisterns), Turkish baths, buildings and barriers. On the precise origins of the Sāruj, a typical product of Iran and of some of the countries located around the Persian Gulf, one can only formulate hypotheses; however, it is still possible to find artifacts dating back to 700 years ago in different parts of Iran.
In principle, to highlight the drawings in relief, in Sāruj bori the use of natural mineral colors is used: lapis lazuli powder for blue, ocher for yellow and so on. Likewise, minio, white lead and cinnabar are used. Mixing these colors can produce extremely showy results.
Among the typical images and motifs of Sāruj bori we find: flowers and plants, gol or morgh, arabesques, scenes of ancient legends and myths, celestial images of angels, portraits of Imām and so on.
To perform the Sāruj bori, two layers are used. The second of these, colored, serves to create the figures in relief.