Make sure that the snack size bag in which you put the vinegar is smaller than the bag that you put the baking soda in. Leave a little bit of air inside the snack bag of vinegar, as opposed to pressing it before sealing and letting the air escape. You need to initially separate the vinegar and baking soda because they react almost instantly, which means that if you poured them in together, you wouldn’t have time to seal the bag before the pressure builds. Adding them in separately ensures that the reaction in the bag will be able to build up to an explosion.
If punching the bag doesn’t partially open the seal, use your fingers to try to pinch the sides of the snack bag of vinegar and pull the seal partially open without opening the larger sandwich bag.
The satchel of baking soda doesn’t have to be completely foolproof, but it should be able to sit without the sides folding down and the baking soda pouring out.
Not closing the bag in time can cause a significantly smaller explosion or it can cause the fizzing reaction to happen before the closing of the bag, so that even when you close the bag it won’t explode.
