On a wall of the Gazi (Kara) Ahmet Paşa Mosque (in the Topkapı district, Istanbul):
a calligraphic inscription on mid-16th century Iznik tiles, in unusual apple green and yellow.
İznik work, named after the town in western Anatolia where it was made, is a decorated ceramic that was produced from the last quarter of the 15th century until the end of the 17th century. İznik town was an established centre for the production of simple earthenware pottery with an underglaze decoration when in the last quarter of the 15th century, craftsmen in the town began to manufacture high quality tiles and pottery with a fritware body (frit being added to clay to reduce its fusion temperature), painted with cobalt blue under a colourless lead glaze. During the 16th century the decoration gradually changed in style, becoming looser and more flowing. Additional colours were introduced. Initially turquoise was combined with the dark shade of cobalt blue and then the pastel shades of sage green and pale purple were added. Finally, in the middle of the 16th century, a very characteristic bole red replaced the purple and a bright emerald green replaced the sage green.
From the last quarter of the 16th century there was a marked deterioration in quality and although production continued during the 17th century the designs became poor, and the city's role as primary ceramics producer was taken up by Kütahya.
Correspondent: J.M.Criel, Antwerpen.
Source: (amongst others) Vikipedia/Wikipedia.