I screenshot 0:16. Won't the heat damage, shatter or explode the glass bowl? I'm not affiliated with that YouTube channel "missevabakes".
I don't think there's enough clarity in the video to answer definitively. So, a couple of critical points:
- The glass bowl should be floating in the water. Otherwise, it could contact a much higher temperature at the bottom of the pan than whatever temperature the water is at.
- The water should be heated with the glass bowl in it already. If the water is already very hot and an ice-cold bowl were dropped in it, the glass could crack or break.
Of course, different types of glass have different resistance to thermal shock. But regardless of the type of glass, treat it gently and with respect. Just because it's designed to withstand abuse, doesn't mean there's any good reason to subject it to abuse, and plenty of good reason to use reasonable precautions. :)
Unless you have a very cheap or extremely cold (think -30 c) glass container, there's absolutely no problem. Even with an extremely cold container, I doubt you'd manage to get it to shatter.
The water will heat progressively and so will the glass container. I melted chocolate this way in various container including glass, never had a problem.