Coloured Glazed Tiles
The most original examples of enamelled wall tiles, to be found in buildings in Bursa, are the coloured glazed (Cuerda Seca) tiles. Tiles of this type are encountered most frequently in buildings dating from the 15th century to the middle of the 16th century in Anatolia, and apart from Bursa and Kütahya, in Istanbul and Edirne as well. We find the finest early specimens in Bursa. The sophistication of the designs and richness of the colours of the tiles used in the Green Mosque, tomb and madrasa (1421-22) as well as in the Murat II Mosque and Madrasa (1425) are extremely striking. In these buildings, all the surfaces, from the borders at the tops of the walls, the details of the doors and windows, the door and window frames, to the altar niches and sarcophagi have been most skilfully covered with these coloured glazed tiles. The altar niches of the Green Mosque and the Tomb and the sarcophagus of Çelebi Mehmet I in particular, feature some of the most exquisite enamelled tiles. Together with colours that had been used ever since the Seljukid era, such as light blue, turquoise, ultra rine and black, colours such as white, yellow pistachio green and gold leaf are also used. The contours between the designs are in black or red. Sometimes sections resembling hard putty in matt red are to be seen between the glazed surfaces. Together with the tiles mentioned in the preceding paragraphs, enamelled tile mosaic was also used in a number of historic buildings in Bursa.
The pattern was applied to these tiles, which were of red clay, by pressing it into the clay or engraving it. Relief designs could also be achieved on tiles according to the mould employed. After the tile has been fired, it is painted with coloured glazes without the use of an undercoat and the tile is again fired. In order to prevent these designs from running into one another, a mixture of beeswax or vegetable oil and manganese is applied. When the beeswax melts the contours that become visible are red, the same colour as the tile clay. Vegetable oil and manganese leave black contour marks. A second method used in Spain is the marking out of the contour lines with thread, which is burnt and destroyed in the firing process. This is why the Spaniards refer to this technique as “Cuerda Seca”, which means “dry thread”. In tiles, to which coloured glaze was applied, dense and complex compositions of plant motifs, flowers such as peonies and calligraphy in the neshi and sülüs styles were frequently made due to the facility afforded by the technique. In plant designs of the Seljukid period, more realistic flowers and leaves, particularly peonies and ivy motifs were used. Calligraphy in the Kufic style became less frequent, giving way to the sulus style. Inscriptions in the latter style were usually relief on a yellow or ultramarine and white background. Intertwining designs create the impression of being multi-layered in places and the forms in relief and openwork ornamentation add further richness to the decoration scheme.
The history of the colored glaze technique goes back to the 14th century Tebriz. This type of tiles were used in the magnificent buildings of the 14th and the 15th century Tebriz, Samarkand and Bukhara. The signatures of master craftsmen from Tebriz are legible in the altar niche of the Green Mosque and are an anonymous “certificate” for the makers of these tiles.
We finally learned the name of one of them from a signature on one of the tiles in the royal pew: Muhammed el-Mejnun. It is generally accepted that the colored glaze technique was used in that area by master craftsmen who migrated from Tebriz to Samarkand and Bukhara in the mid-15th century. The stone inscription on the royal pew of the Green Mosque states that all these decorations were carried out under the supervision Ali İbn İlyas Ali, from Bursa. The latter had joined Timur's army in 1402 and reached Samarkand, where he learnt the technique. Upon his return to Bursa with the craftsmen from Tebriz, he began to work on enameled tiles. Flowers such as peony and lotus are seen on tiles where colored glaze have been used and a more realistic style, even more than the Seljukid style, reflects the influence of the Far Eastern art, which reached Anatolia with Timur’s army and the master craftsmen. No definite conclusions have been drawn about the places where these tiles were produced, which were made with a technique that had been brought to Anatolia from Iran. Only a few pieces of colored glaze tiles have been revealed by excavations at İznik. It is highly probable that the examples found in Bursa, Edirne and İstanbul were produced in temporary workshops in all these three cities at the same time. The tiles used in these three centers differ as far as design and quality are concerned. However excavations have so far failed to reveal any trace of tile workshops.