I am doing a volcano cake next weekend, and I am going to do the actual volcano out of rice krispie treats and put a baby food jar (the larger size) in the top for dry ice smoke effects... My question is this: How much dry ice do I use? How much do I buy to have smoke for a couple hours? I can have it in a cooler (although not sealed, I do know not to seal it completely) and "refill" it as necessary, but I have no idea how fast it submlimates, etc. Anyone ever do this? Thanks in advance!

I did a similar cake with a volcano on top - molded the rice kripsie treats around a small glass. Chopped up some dry ice and then kept spritzing with water. I had practiced before the wedding but couldn't come up with a good method to keep it smoking. What I found when I poured too much water over the dry ice during practice - it just became a solid block of ice. Ideally you need a pump to keep pouring water over the dry ice. I kept the dry ice wrapped in newspaper and towels in a cooler. Took along a good ice/chocolate chipper. Also, make sure to take along heavy gloves to handle the dry ice.