How TNT Pop Its Snappers Work

The Chemistry of Pop Its and Bang Snaps

Pop It and Bang Snaps are sold with small fireworks or in novelty stores for pranks.
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TNT Pop Its belong to a class of novelty fireworks collectively called bang snaps. Similar products are called snap-its, poppers, and party snaps. Kids have been using them for pranks and celebrations since the 1950s.

In case you were wondering, Pop Its don't contain TNT. That is simply their brand name. Pop Its are trick noisemaker "rocks", commonly seen around the 4th of July and Chinese New Year, that pop when they are stepped on or thrown against a hard surface. They look like little paper-wrapped rocks, which, in fact, is what they are.

The "rock' is gravel or sand that has been soaked in silver fulminate. The coated grains are twisted into a piece of cigarette paper or tissue paper. When the bang snap is thrown or stepped on, the friction or pressure detonates the silver fulminate. Pop its can also be ignited, although it's not particularly safe to set them off in your hand. The tiny explosion makes a sharp snap that sounds a bit like that of a cap gun.

Chemistry of Pop Its

Silver fulminate (like mercury fulminate, which would be toxic) is explosive. However, the quantity of fulminate in Pop Its is very small (about 0.08 milligrams) so the little exploding rocks are safe. The sand or gravel moderates the shock wave produced by the detonation, so even though the sound is loud, the force of the pressure wave is fairly minor. Snapping one in your hand or stomping it with bare feet can hurt, but is unlikely to break the skin. The sand or gravel isn't propelled very far, so there isn't danger of the particles acting as projectiles. Generally, Pop Its and related products are considered safe for use by children. While poisonous fulminates of other metals would produce a similar effect, they aren't used in commercial products.

Make Pop Its Yourself

Fulminates are easily prepared by reacting metal with concentrated nitric acid. You don't want to go making this in any quantity yourself because the fulminate is shock sensitive and pressure sensitive. However, if you decide to make do-it-yourself Pop Its, the silver fulminate is more stable if flour or starch is added to the crystals during the filtering process. You can coat sand with silver fulminate, wrap it in paper, and use it in the traditional way. Bigger is not better — be safe.

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Helmenstine, Anne Marie, Ph.D. "How TNT Pop Its Snappers Work." ThoughtCo, Sep. 3, 2021, Helmenstine, Anne Marie, Ph.D. (2021, September 3). How TNT Pop Its Snappers Work. Retrieved from Helmenstine, Anne Marie, Ph.D. "How TNT Pop Its Snappers Work." ThoughtCo. (accessed December 8, 2022).