[Easy] Baking Soda \"Grenade\" As known basic salts react with acids. Carbonates release some CO2 during the process. This can be used to cause small harmless "explosions". I experimented with these some years ago. I found out that the best acid to use is citric acid (dosn't smell and is very mild). My "grenades" had about a quarter of the power of a champagne cork. So these did a small bang and cool foam effects. Do this at your own risk. Don't use strong bases or acids (like alkali hydroxides or non-organic acids). This way the speed of gas production isn't too big and the by-products are almost harmless. Also eye gear recommended because this might pop in your hands. Use also small amounts of salt and acid and don't use strong containers that would allow the pressure to build up. Also make sure that there are no materials near that could be stained by the foam and no electric cables or sockets nearby (the foam might cause a short circuit). Recepie for a baking soda "grenade": (the exact amounts aren't so important, but use small amounts in the beginning) Parts: a small sealable plastic capsule(a film can,a surprise egg inner capsule (preferred, but i don't know how widespread are these), etc) Some citric acid (crystal, not solution preferred) Some baking soda Some water 1. Make sure that the capsule is empty (don't ruin your negatives). 2. Add a few millilitres of acid (make a solution if you have crystal) to the bottom of the capsule. 3. Add a drop of water to the baking soda to make a clay-like mass (i also used gelatine to do this, but just water is simple). And attach a small pellet of it to the top part of the capsule. Make sure that it doesn't fall down so easily or the "grenade" pop suddenly. 4. Close the container so that the acid is on the bottom and the baking soda pellet is attached to the top part (so they can't react yet). 5. Experiment with it in safe environment where there are no people nearby. Either throw it or knock it over with a stick. Then the baking soda reacts with the citric acid and in a second or so the capsule pops open with a small bang and with foam flying out of it. The best resuts are achieved by experimenting.