[sixsixstang351]

Hey, first post, interesting forum.  Trying to run a few experiments, which may or may not be to concept test some ultra-secret new product idea I'm pondering *sneaky*  Or it could just be a nerdy and unnecessarily elaborate office prank. 

Long story short, I'm looking for suggestions on substances to use that, when mixed, product a manage-able expansion / pressurization of a small pressure vessel.  The amount of expansion / pressurization I'd like to see is roughly on the order of a standard latex/rubber balloon, going from empty to full. 

I'm sure there are a million potential solutions/chemical reactions that would meet this basic goal, so to help narrow it down it'd be good for the reactants/reagents (i'm a mechanical engineer, apologize to all the chemistry savants who I am offending with my terminology lol):
* non-toxic / won't hurt people if the balloon pops
* readily available
* inexpensive is good here (as usual)
* easily shipped / stored / stable
* some heat can be released during expansion, though it can't be so much that it melts the balloon (or affects dyes/coloring on the balloon, or harms a user... so like... maybe 60C for a brief period is okay, or 5-10C above room temperature for a while, but no 110C burning balloons)
* ideally the expansion would be over 30s-a few minutes (don't want it to take a fraction of a second or 2 hours)

In this experiment.... within the balloon, a small break-able bladder will be sitting there, and when the bladder is broken (through some input from a human or other), it mixes with whatever else is in the balloon, and then you get expansion. 

SO yeah... any guidance on some reactions to look into would be great!  If you need more info from me let me know. 

[imnotkemist]

dry ice and water works. just use a small amount.. really small