Building a smoke-emitting bomb is a fairly simple exercise in chemistry. The most common variety of smoke bomb uses potassium nitrate (KNO3) and sugar; both are non-toxic, though ingesting KNO3 in large amounts has been linked to cancer. KNO3 is sold at hardware stores as stump remover and can also be obtained as a fertiliser. Smoke bombs are great for fireworks, paintball and war re-enactments.
Combine a mixture of 60 per cent KNO3 and 40 per cent sugar in a cup, add the lid, and shake the two together to form a homogeneous mixture. The mixture should not exceed 100 grams.
Pour the mixture into the saucepan and set the plate to a medium-high temperature; stir the chemicals consistently and scrape any material on the bottom.
Heat the mixture until it has the consistency of peanut butter and remove the pan from the plate.
Scrape the mixture out and fill the cardboard tube. Several batches will be necessary to fill the tube completely. About 3/4 of the way through the tube, set a fuse inside and apply the material around it. The mixture hardens after about five minutes, so be prepared to insert the fuse quickly. Once the tube is filled, the smoke bomb is ready.
You can seal the smoke bomb in wax to waterproof it.
Always wear goggles and gloves when handling combustible materials. Avoid making batches larger than 100 grams at a time.