Creme Brulee, Kilner jars and Sous Vide - heat up fast or slow?

Question

I normally use bags for my Sous Vide recipes but I have invested in some genuine Kilner jars to make Creme Brulee.

America's Test Kitchen places the custard in sealed jars in the hot 180F (83C) bath. Other online chefs recommend placing the jars in a cold bath and bringing the water up to temperature to prevent the jars shattering.

While I trust ATK, the thought of shattered glass and egg mixture getting into my circulator doesn't inspire me. Would the more cautious approach be better, assuming there is no food safety risk as the temperature will come up fairly quickly? Or are genuine Kilner jars more robust than many equivalents?

https://youtu.be/HlMUp2AhnBY?si=QirGSJtS8QHb049l

Answer 1

According to the Kilner website, genuine Kilner jars are made from borosilicate glass which is freezer, oven and microwave safe.

So yes, these can be placed in a Sous Vide bath without concerns. Other varieties may not be made of the same quality glass, hence the gentle warm up time.