Why sometime glass vase cracked by itself?
Good question. Sometime, it does. You may have the experience when you light a candle in glass floating bowl, the heat of lighting the candle may crack the opening edge of bowl. This phenomenon is also often occurred when the glass removes from a cooler to room temperature surrounding, or a vase is put in warm water. Glass has expansion too, when the temperature is changed, like most of materials. The problem is, glass is very hard and solid, when the temperature changed outer of glass; it starts to shrink (cooler). However, the inter glass still retains the temperature and not shrink, so the shrink force “tears” the glass outer surface, it is cracked.
