Decoration Techniques Used in Ottoman Tiles
Plain glazed vessels, sometimes with overlays, feature prominently in Ottoman works of earthenware where red ceramics body was quite common. With these, the color is usually green, with light turquoise or yellow-brown also used. This was also the case with tiles. Glazed bricks, a kind of Seljuk tradition, were successfully implemented in the minaret of İznik Green Mosque, while hexagonal tiles, some green and others turquoise, were found in the excavations of Orhan Imaret.
It was common practice to glaze thick tile slabs with red ceramics body in one color. This method was also used in glazing glazed bricks, which are a kind of tile. Ornaments made of glazed brick slabs in the palaces of Ramesses II and III in ancient Egypt, in Ur and Susa in Mesopotamia, in the 12th century BC Assur and Babylonia maintained their artistic value well into the Achaemenid era continuing until the Parthian period. This type of glazed wall covering, which seems to have disappeared during the Sassanid era, could only reappear in early Islamic art in Samarra and with wall tiles made with different techniques in Egypt and North Africa. In the period called the Great Seljuk Age, architectural decorations, especially in regions surrounding Iran, were also based on plain glazed bricks, applied together with bricks.
Putting earthenware to side, the colored glaze technique used for tiles mostly in the early Ottoman period was interpreted by applying the mosaic tile technique, originating with the Seljuks and successful examples of which were also seen in the early Ottoman period, on a single slab. In fact, in some applications of the mosaic technique in Bursa, where white contours are widely visible on the plaster floor, attempts were made to use the pieces side by side in such a way that the plaster floor disappeared. Applying on a single slab non-flowing colored glazes with clear contour lines to suggest the curves of thinly folded leaf motifs allowed for a very vibrant and colorful interior. The Green Mosque and Tomb in Bursa can be considered the most successful examples of this technique. At times, sections separated by scratching, or covered with glazes of different colors, are separated by depressions or raised contours, depending on the method used. While the contours applied with yarn or sugary materials are baked in the oven, contours are formed and the mixing of colors is prevented. This technique, which involves the using of threads in Spain, is called “cuerda seca”.
The usual decoration of Ottoman wall tiles after the early period was carried out using the underglaze technique. The crucial difference of İznik made tiles is the ceramics body, which is made of 80-82% quartz fritte and 18-20% binding clay. The fine and harmonious lining and the expansion coefficient covering the decoration along with vivid patterns represented the typical underglaze technique of the era. Tiles coming out of Kütahya and the Tekfur Palace show that there were differences in the composition of tiles manufactured locally, far from the center and İznik.
Although it is a very simple process to remove the ceramics body from its natural environment and prepare it when making works of pottery, it requires a long effort with earthenware and tiles. With the fritted ceramics body, which is the defining feature of Ottoman earthenware and tiles, the clay is only binding to a small extent while the expansion harmony of the glaze covering it with a mixture of free quartz and silica, creating a hard and solid infrastructure, reinforces the quality of the tile (‘Anadolu Toprağının Hazinesi Çini’ (Tiles, Treasure of the Anatolian Lands), Belgin Demirsar Arlı and Ara Altun, pp.15-16).