Thursday, May 13, 2010

Smoke Bombs (United Nuclear)

Light a tiny piece of this solid mixture (about the size of your thumb), and it makes a giant cloud of smoke in seconds!

By far, the most common smoke formula is the Potassium Nitrate/Sugar formula. It produces a white-gray smoke and is both easy, inexpensive & fun to make. The percentage of Potassium Nitrate and Sugar in this composition vary somewhat depending on who you ask, but the 60/40 mix listed below is pretty common.

A lump of this stuff the size of your thumb produced the
smoke cloud on the right in under 2 seconds.

Potassium Nitrate 
60 %
40 %

  • Although the two ingredients can just be finely powdered and mixed together, in recent side-by-side tests, we found that melting the two together does in fact make a superior Smoke Bomb.
  • To melt the mixture together, you'll need small metal saucepan or other heat resistant container, and an electric hot plate. An electric hot plate is preferred to an open flame heat source because it's a tad safer, and easier to prevent overheating of the mixture.
  • The mixture must be heated slowly, and over a low heat until it just starts to melt.
  • Heating it too quickly, or at too high a  temperature will cause it to turn black, burn & ignite making a giant mess, not to mention a fire hazard. In any case, this should all be done outside just in case you overheat it does happen to ignite. As the mixture begins to melt, it will turn brown and look exactly like Carmel Candy... see image above After all, you are melting Sugar (and no, you can't eat it).

A Note About Potassium Nitrate
Unfortunately, sales to the public of most oxidizers (such as Potassium Nitrate) are being limited by various Federal agencies. Several readers tell us that there is a Tree Stump Remover product available at lawn care & plant/nursery stores that is close to pure Potassium Nitrate. Although may people have reported good results using this as an easy to obtain replacement for Potassium Nitrate, we have never tested it, nor can we comment on how well it might work.

A step-by-step procedure is outlined below....


Start by making a small size batch (50 grams total). Measure out 30 grams of Potassium Nitrate and 20 grams of Sugar into a small cup. For those of you who cut math class, 30 grams of Potassium Nitrate and 20 grams of Sugar is still a 60% / 40% mixture. If you make a batch larger than 50 grams, it will be very difficult to mix and heat evenly. You can always make more, so don't mix up a giant batch.

Snap a lid on the container and shake to mix the two chemicals together. Pour the mixture into a heat resistant container and set it on your hot plate.

Set the hot plate temperature to medium-high, and about every 30 seconds or so, stir the mixture well, being sure to scrape the material that may start sticking to the bottom.

Over the next several minutes, the mixture will begin to darken and clump. It will soon begin to look like brown sugar, and when it finally mixes smoothly and looks like peanut butter, it is done. If you mixture is turning BLACK, you're heating it a too high of a temperature.

Remove the container from the heat, and scoop out a lump of the sticky mass. You can either just plop some on the concrete, or if you're picky about the way your smoke bombs look, you can make small cardboard molds and press the gooey mass into them. Personally, we just lay it on the concrete.

Before the little blob cools, insert a small piece of Visco Safety Fuse.

Do this to the remainder of the material and allow them to cool and harden.

In about 5 minutes, the material will be cool and become rock hard (beware that it will stick to the surface while cooling, but is easily removed with a little knock from a hammer). Set your Smoke Bomb away from any flammable materials, light the fuse and stand back.
These smoke bombs burn fast and sometimes will jump around a bit. They do produce a little flame when burning, so be careful not to ignite them in or near dry grass, papers, etc.

The smoke from this mixture is essentially non-toxic, but that doesn't mean you should stand in a cloud of it and breathe it all day long.
Like any smoke from burning material, people may be allergic to it, or is my cause eye irritation in some more sensitive folks.

Colored Smoke

Unfortunately, colored smoke mixes are a totally different animal. The nitrate/sugar mix cannot be colored. Colored smoke mixes use an entirely different cool burning mixture and vaporize special low-temperature Aniline dyes to produce colored smoke. These Aniline dyes are difficult to come across and very expensive. We've never found a reliable source for them.

- United Nuclear

1 comment:

  1. Nuck

    Sorry about being a little late to the party.

    I find that it is easier to mix a double batch of the candy at once. Basically, it's the same amount of toil and trouble to do twice as much at a time.

    The stump remover is the "Spectracide" brand. And , yes, it is pure potassium nitrate and works great as rocket fuel, but I've never tried to create copious amounts of smoke with it.

    I am not familiar with any ban or controls on saltpeter. You might try a farm supply as it is sold as a "nutrient" and fertilizer. I just picked up 5 lbs of potassium nitrate and sulfur from the same supply with no questions about where I was located or what the intent was. There are a few substances that contain both of those chemicals, but black powder is the end result for some of it and the rest is the candy.

    You're correct about the slow heat. I'm going to go with a double boiler on the next batch to see if it helps to homogenize the mix.

    As for your deal, you can use an old coffee grinder and do both those chemicals together, and your end product will be noticeably superior to what you're getting currently. It might not seem like grinding it up just a bit smaller would effect it all that much but you'd be surprised.

    Have you tried substituting charcoal for 10% of the potassium nitrate? Or either dextrin, which is baked cornstarch, or karo for some of the sugar?

    I would think that your smoke would certainly be smokier with the charcoal. Especially.

    There is also sawdust, soft wood finely ground to almost a powder and going with ≥5% of that in the mix.

    You can grind all of them with the mix except the charcoal, but that's because of potential impurities, in the charcoal. One tiny speck of ferris metal can get you a nice spark and if it hits the moving blade.

    A couple drops of water and not a bit more will actually help it emulsify much quicker, it's easy to go overboard and with a 200 gram batch, I use Hess then a 1/2 teaspoon, total.

    Now, about that smoke. It is absolutely toxic, there is carbon monoxide in there and can quickly give a individual that's sensitive to potassium an allergic asthma Ike anaphylaxis that can make it their last smoke bomb, so be careful.