Given the elaborate nature of the decoration on many of the Islamic bowls, dishes, ewers and other forms of utilitarian pottery it made sense for artisans to create moulds from which many copies could be easily and efficiently made for commercial production.
In fact there were even master moulds made from which “negatives” (a series of moulds for dissemination among commercial potters) were produced. The master mould would show all the decoration as it would appear on the final item. The “Negative would show the decoration in mirror image and reversed so that relief decoration would show as incised and decoration that would show as incised on the final object would show in relief on the negative mould.
In categorizing moulds we might say that there were moulds made to shape each of the top and the bottom of vessels as well as the inside and the outside of vessels.
The master mould would be formed in clay and hard fired in the shape of and with the design looking like the final item would. It would then be used to generate the negative moulds. Soft clay would be pressed around the master and then separated by splitting the negative mould either horizontally or vertically. These negatives would in turn be used to create impressions in two or more parts that would be attached together, often creating visible seams on the final item.
The making and supplying of moulds became a distinct trade, with skilled designers able to supply numerous workshops, enabling them to make wares of a quality they would not manage on their own.
Ceramic moulds have to be made of an absorbent material that dries the surface of the clay pushed into it, causing it to shrink slightly and detach from the mould walls. The moulded piece can then be removed from the mould without sticking or spoiling. The mould would then have to be dried before being used again. This would be a relatively slow process even in a hot climate.
This Master would have been used to create other moulds of the upper half of a vessel such as a jug or pitcher. The top of the soft clay impression would have been cut away and have a neck or spout attached to it. The bottom would have been attached to a complementary bowl-like molded piece. The sharpness of the incised calligraphy around the entire body of this master mould and scrolling foliage make this an elegant and lively example.