What kind of craft does "no Jin Gangzuan, no porcelain worker" come from?

What kind of craft does "no Jin Gangzuan, no porcelain worker" come from?

1. Dental porcelain

2. porcelain

Correct answer: baked porcelain

"Without Jin Gangzuan, don't take porcelain work." It is the traditional craft-enamel. Porcelain is hard and wear-resistant, but it is also fragile. Unfortunately, porcelain is useless, so it is discarded after being broken. As a result, craftsmen invented Jin Gangzuan and shovel nails, resulting in the industry of shovel porcelain.

"Curved porcelain" is a technique to repair broken porcelain with a metal shovel like a staple.