6 pcs 20mm porcelain seaweed nigra Its a difficult glaze to

Its a difficult glaze to picture

These are about 15mm and sold in different sets

These are 24-25mm buttons sold in sets of 5

These are 24-25 mm buttons sold in 4x sets

6 pcs 20mm porcelain seaweed nigra Its a difficult glaze toPorcelain buttons seaweed . These are about 20mm and sold in a set of 6. The buttons were fired two times. First firing is the so called bisque firing where temperature goes as high as 1000C degrees. After that our buttons are ready to be glazed. We put 2 layers of glaze manually and when they've dried, buttons are fired for the second time at about 1230C degrees. The backside of the buttons stays unglazed. Its like a stone to the touch. Can you wash