A few days ago, I was creating a solution which involved boiling water. I had two 4L beakers on identical hot plates. After around 10 minutes, the first one boiled. Waiting another 30 minutes, the second one had still not started boiling, although small bubbles had formed at the bottom. Shortly afterwards, I heard a ping and the second beaker cracked and leaked water.
Is there any possible correlation between the long boiling time and the beaker breakage? Both beakers should have been heat-safe, although they were from different brands. I'm not convinced of the cleanliness of the beakers, so if this could've been caused by a contaminant, that's a definite possibility.