What is the purpose of using ping pong balls on top of a Sous Vide Bath? I recently saw a picture of expert Douglas Baldwin with his sous vide equipment in this article.  One of his immersion circulator baths was covered with ping pong balls.



What is the purpose of covering the immersion circulator bath with ping pong balls?
It is to lower the water evaporation from the bath, and keep the temperature of the bath even.

The concept has been used in chemistry labs for years! But normally, the balls are smaller and made of polythene - those are a bit big.