- jello takes a while to set, generally overnight. If the jello had additional endothermic ingredients, it would set faster. Cool!
Use that stuff that heats your gloves up when skiing - great things! - for other uses also:
- an exothermic tea bag (great for camping trips)
- self baking beans: open can and the material reacts with the air to head up
(obv. making the assumption here that the material isn't toxic!)