Dry ice to keep cooler cold

[Nimrod3388]

I was thinking of using a small cube of dry ice instead of frozen 2 liter bottles in my cooler (5 gal carboy). I know the ice will need to be insulated and not in contact with the glass for it probably will crack. I figure if I can determine the best size it should keep the brew cool. Has anyone done this before or is this a big risk?

 

[PseudoChef]

It's going to melt rather quickly. Plus, water can only get so cold. I'd stick to ice.

 

[DeathBrewer]

do you get the dry ice free? if not, that could get expensive.

 

[Philip1993]

If you keep it trapped underwater, it will develop a layer of ice on the outside that will slow the sublimation a whole lot.