The missing porcelain around the lid rim is usually caused by the lid being dropped or banged against things. It is commonly referred to as rim rash. The small round spots of missing porcelain on the bowl usually occurs where the grate straps are welded to the inside of the bowl. They are commonly referred to as porcelain pops. It is very common with colored kettles, but for some reason does not happen anywhere near as frequent with black kettles. As to the cause, I have seen it discussed on the Forum that it is due to uneven heating and cooling of the porcelain because of the extra metal where the grate straps are welded.
From Wikipedia - Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C (1,380 and 1,560 °F).
Topic: Porcelain pitting! (Read 720 times)
