DISCLAIMER: Neither I, nor anyone associated with "The Real Gun Guys" accept any responsibility for what you choose to do with the information presented below.
In other words, you're on your own.
That said, the procedures presented are perfectly safe and have worked just fine for me in the past. While there are other methods, this is the one that I use and it works just fine for me.
Smoke Bombs have many uses, concealment, pranks, diversions, celebrating the birth of our nation, signaling for help, or just plain fun. The term "Smoke Bomb" is a misnomer, as this device doesn't explode, it merely burns fast and hot. However, I wouldn't confine one. That's never a good idea.
Don't let the following procedure intimidate you. If you can make caramels, you can make smoke bombs.
The recipe for a simple smoke bomb is as follows:
6 parts potassium nitrate (fine white granules)
4 parts sugar (granulated)
1 cleaned and dried standard sized soup can.
6" length of cannon fuse
Potassium nitrate (Salt Peter) can be found at Wal-Mart as Spectracide Stump Remover for $5 a pound. Don't get the Green Light Stump Remover, it's not potassium nitrate. Sugar is of course available almost anywhere for next to nothing.
Usually formula ingredients are measured by weight (Black Powder is for example), but I measure my ingredients for this formula by volume and have had good results. Today, we're going to make a soup can sized smoke bomb.
Take 9 oz by volume of potassium nitrate and 6 oz of granulated table sugar and mix them together completely. At this point you could just stick in a fuse and light it, and it'd work just fine, but you will get better results if you keep going.
Take a small stainless steel kettle and put it on the stove. Set the burner to medium and put in your potassium nitrate and sugar mixture. Stir occasionally with a spoon and be patient, do not turn up the heat to try and hurry it up. After a while the mixture will begin to stick to the bottom of the pan. Keep stirring every three of four minutes until the mixture melts and looks like runny peanut butter. That's the sugar caramelizing. You can go a little further if you want, but there's little need. At this point you could mix in powdered dyes to change the color of the smoke, but we're not going to do this. This formula produces white smoke.
BE CAREFUL - THIS MIXTURE IS EXTREMELY HOT!
Take you're cleaned and de-labeled soup can and pour your melted mixture into it. Use potholders as the can will be very hot! Set the can someplace out of the way where it can sit undisturbed. The mixture may bubble up a bit and foam over, as it is still cooking in the middle. When it has cooled, but still pliable, insert your fuse (if you have it) in the middle and secure it with the cooled mixture. Let sit more until it has fully cooled and then store if an airtight container (I use Ziplock plastic bags) as the cooled mixture is very hygroscopic.
This formula ignites easily and all that is really required is a match or lighter, but a fuse makes it more convenient. Place the smoke bomb in an area away from any combustibles and light the fuse. Get back at least ten feet. If lighting without a fuse, do so very carefully.
The smoke bomb will burn fast and hot, while hissing loudly the whole time. It also produces a prodigious amount of smoke. I suggest you not light off a smoke bomb this big in a residential area unless you want the fire department to show up. A smaller, golf ball sized smoke bomb made from the same formulation will be more than adequate. All you would have to do then is pour out the melted mixture onto a greased flat baking pan and when it cools sufficiently, form it into little balls. You could also put the fuses in them at the same time.
How it works:
I'm no chemist (and if you are one, you're probably going to cringe at my explanation. Feel free to write me at the address on the left and I'll correct anything I got wrong.), but basically it works like this. The potassium nitrate is an oxidizer and provides the oxygen, and the sugar is the fuel. When mixed in the proper proportions, the sugar burns completely leaving little ash. Sugar will burn just fine on it's own, but it's slow and dirty. Mixed in a dry mixture with the potassium nitrate, it burns better, but still leaves a lot of hot, sooty ash. When cooked together the potassium nitrate is more completely and closely bonded with the sugar and thus it burns significantly better. A golf ball sized smoke bomb will only leave a round scorched mark on the pavement.
In closing, have fun and be safe. Feel free to leave me feedback or questions about this post at the address on the left.