With each firing, the enamel shrinks, so the crevice has to be filled with more enamel and fired again until the hole is completely filled.
加溫一次，琺瑯質便收縮一次而致凹凸不平，需要用同樣顏色的琺瑯多次填充。經過多次填燒，直到每一小部分都已充滿而毫無凹坑，加溫的程序才算完成。