Do bubbles on a bath insulate the water, or cool it faster?

Question

Will a layer of bubbles on a hot bath keep the water hot longer by insulating it from the cooler air, or do the bubbles cool the water faster by increasing the surface area of the water (since the outside of each bubble is a bit of the bath water)? Or is it a wash? (Sorry for the bad pun, please answer the question anyway.) Maybe it depends on how smooth or irregular the top of the bubble layer is?

Answer 1

It insulates it. While there is a large surface area, there is no mass behind that surface, and so even if these surfaces cooled, they are more or less insulated from the large mass of water below them by the contained air, so that even if they got quite cold, they would not absorb much heat from the bath.

It is really the same principle as any foam insulation: that not much heat can travel in the thin structures OF the bubbles, and not much heat travels though the air BETWEEN the bubbles.

Enjoy your long, warm, bubble baths!