How to Make a Smoke Bomb the Failsafe Way—We Thought!

How to Make a Smoke Bomb the Failsafe Way—We Thought!

Written by Harry Gilliam

Topics: How to Make Fireworks

Sometimes, learning how to make a smoke bomb using colored smoke can be tricky. Even if you already know how!

Because even if you really do already know how to make a smoke bomb, you can still have problems getting your colored smoke to work…problems you may not expect.

How to Make a Smoke Bomb the Failsafe Way—We Thought!

Skylighter has been offering organic powdered dye pre-mixed with the other necessary colored smoke chemicals for years. These premixed colored smoke components make it a lot faster and easier to make smoke grenades and make smoke bombs. We even got Ned Gorski to write an excellent and detailed project article on How to Make Smoke Bombs, complete with color photos, and even videos.

Skylighter sells that pre-mix as “colored smoke mix.” You buy a pound of the colored smoke mix, combine it with a pre-measured amount of just one other chemical, potassium chlorate, load it into a capped tube, and voila. You have a homemade smoke bomb, ready to light.

Usually.

Except, now people were having problems getting their colored smoke to light.

When this problem started to show up repeatedly, I finally decided to roll up my sleeves and look into it. What I found, though anything but earthshaking, is a good little lesson in simple pyrotechnic detective work.

And it is exactly the same kind of problem diagnosis and solution, which anyone who makes fireworks will eventually run into.

So, ride along with me a ways. It won’t take long, and there are a couple of good tips and tidbits that anyone can use.

What we try to do with our colored smoke bomb kits is make it really simple, fast, and idiot-proof to make a smoke bomb. But in trying to make it too simple, we may have overlooked the obvious.

Here was the problem: Customers were mixing the correct weights of the two-part colored smoke components (smoke mix and potassium chlorate) correctly—according to the instructions Skylighter provided. But when they tried to light the stuff it wouldn’t burn. Or it would light, and then go out.

Now when you light colored smoke it is supposed to smolder, not catch on fire.

The key is having exactly the right ratio of the potassium chlorate oxidizer to the smoke mix fuel. Screw the ratio up one way and your mix will burn too fast.

This is very important. If your mix actually burns, you won’t get the colored smoke you want. Just black, brown, or some other characteristic dark color of burning material.

Screw the ratio up the other way, and your colored smoke mix will not ignite at all.

Colored Smoke Detective Work

When we first heard about the problem with a single colored smoke color, we simply took some of our smoke mix here, mixed it properly with the potassium chlorate, and burned some outside.

Hmmm… there is some kind of problem. Perhaps the company, which formulates our colored smoke mixes, changed the brew in some way. They said not, but chemicals can be different, from batch to batch, or year to year. And unless you do time consuming and expensive testing of each batch you get, you might never know. So, we all tend to rely on good suppliers, brands, and model/spec numbers instead.

Making our smoke mixes does involve carefully weighing and blending at least 3 different chemicals.

It did visually appear that the blending/mixing was not as thorough.

But hundreds of pounds of these colored smoke mixes were already out on the street in customers’ hands. What to do?

We found that if we increased the amount of chlorate added to the smoke mix, that we could get it to burn. So that’s what we recommended to people who were having problems. We even sent out additional potassium chlorate at no charge, and replacement smoke bomb kits.

The problem reports continued nonetheless. Some people were not able to add additional chlorate and solve the problem. And then other colors started to have the same problem.

Hmmm… what else could be wrong?

A little background will help here. Because colored smoke dyes are “dirty” to work with, we recommended that folks use “bag mixing” to mix the chlorate and smoke mix.

Basically, this involves dumping the two parts into a big zip-lock, sealing it, and then mushing the contents around for a while until there’s a homogeneously colored powder inside with no lumps.

The theorem I developed was that for reasons unknown, either or both of the two-part smoke mixture had either increased in particle size and/or gotten “clumpy”—a scientific term describing what happens when a chemical gets a little bit of moisture in it.

Well, for sure the chlorate had. You could look at it and tell.

I ran some of our blue smoke through a 30-mesh kitchen strainer and found the same thing. More clumps. Maybe even larger particles.

So, here’s a lesson in pyro 101.

When we first started offering two-part colored smoke kits, it’s a fact that both the colored smoke fuel and the potassium chlorate were very fine (particle size), free flowing powders, something you almost always want in your fireworks chemicals.

And we had no reports of problems igniting the smokes.

Now, with lumpy, clumpy material, what has happened? Well think about it. It’s simple. The particle size of both parts has increased. When particle sizes are larger, surface area is decreased.

Since the pyrotechnic burn we want depends on many little particles of fuel and oxidizer being in close contact with each other AND since we know we had that balance exactly right when the two powders used to be fine powders that were free flowing, then the surface area is no longer adequate for the ratios we were using.

And that’s exactly why adding a little more potassium chlorate had solved the problem for some people. The large surface area problem meant that if we changed the ratio of oxidizer to smoke fuel, we could indeed get the smoke to light again.

But over time as BOTH fuel AND oxidizer got clumpier and clumpier, even that solution didn’t work.

Why? Because the mix was simply too coarse to take fire using the bag mix with the two chemical components we were providing.

The Tests

Experiments proved this out. Armed with the info above and my theorem that it was merely a particle size problem, I set out to solve the problem AND try to do it in a way that would involve the least hassle and expense for both Skylighter and our customers.

It took about two hours. Like most of my testing, I try to work with very small batches. This speeds up the process by reducing weighing, milling, and mixing. And reduces the cost of materials, a lot of which is often wasted doing the testing.

I was pressed for time; so I had the guys in the warehouse, first pre-measure a lot of little baggies of potassium chlorate and colored smoke mixes.

I took the box of this stuff home, realizing only later that the little white powder bags could have brought big smoke down on me, had I been stopped with them. (“No, no, no, ossifer. Those little white powder baggies aren’t what you think at all. Actually, if I mix the white stuff in with this colored stuff, and light it, you will get purple colored smoke! Wait, ossifer, I am not trying to burn the evidence. No, wait. Stop. Those things are too tight on my wrists. I wanna call my mama, ahhh lawyer!”)

First problem was finding someplace that wasn’t windy. I don’t do this stuff indoors in my shop any more, and smoke dyes are easily blown around by even stray puffs of wind.

I found a corner against a shed, out of the wind, and set up my scale, two coffee grinders, some mixing cups, a small kitchen strainer screen, and my trusty pyro notebook.

I aimed for a ratio of 14.2 grams of smoke mix to 5.2 grams of potassium chlorate. That’s the ratio we devised early on that would work with all of our smoke mixes, regardless of color. And we knew from history it used to work.

My test burn container for all experiments was a 9/16” ID x 1-1/2” long tube (called an M80 tube in some circles) with a cardboard plug in one end, the other end open.

FYI, colored smokes do not have to be confined to do their thing. I left one end of each test-tube open for the tests.

Experiment 1: I added the two chemicals together in a zip lock and sqwooshed ‘em together for ten minutes. The now infamous, bag mix method. Filled a test tube, inserted a piece of Visco and lit it. Failed to light. This mix would not even light when directly blasted with a blowtorch.

Experiment 2: I repeated the process in Experiment 1, but with an additional 10% potassium chlorate. Lit the fuse, and it too failed to ignite. Blowtorching the loose mix caused it to light, but it could not sustain the burn, and went out.

Experiment 3: Repeated #2 again adding +10% chlorate, but instead of bag mixing, screened the mix 3 times. Lit the fuse, and the smoke mix ignited, the burn was sustained, but with a “sputtering” burn, and an okay, but not rich blue smoke.

Experiment 4: Since the potassium chlorate was the lumpier of the two components, I used a coffee and spice grinder to grind the chlorate to a fine, fluffy powder, with about 20 seconds of pulse milling. Weighed the two components in the original 14.2/5.2 grams ratio. Screened the two components together 3 times. The mix burned correctly.

Experiment 5: Repeated #4, but I also blade milled the smoke mix for 20-30 seconds as well, before screen mixing together 3 times. The mix burned even better. Full rich blue smoke. The volume of smoke was the greatest of all the test burns.

Conclusion

The particle sizes of both components need to be as small as possible. If there is a problem getting the smoke mix to burn, then milling both components separately to a finer particle size, as well as using a better mixing method will likely solve the problem.

This will not solve all fireworks mix problems. But if you think particle size or clumping may be your problem, the method described above is a quick and simple test to find out.

Cost: Cost to solve the problem at Walmart–$34: 2 coffee mills, $14 each; one small wire strainer, $6. And everything is reusable later on in my fireworks shop.

More on cheap chemical milling using a coffee (blade) mill.

Tell Me What You Think: Was this Article Helpful to You or Not?

Just leave a comment below. Thanks.

- Harry

105 Comments For This Post I'd Love to Hear Yours!

  1. Bruce says:

    I’m confused (often happens). You write the following: “Experiment 5: Repeated #4, but I also blade milled the smoke mix for 20-30 seconds as well, before screen mixing together 3 times. The mix burned even better. Full rich blue smoke. The volume of smoke was the greatest of all the test burns.”

    but in your link you say not to blade mill oxidizers with fuels. Help out an old timer.

  2. Eric says:

    Powered dye works great for adding color. Also, I hear you can use baking powder to make the smoke pour out more steadily, but have never actually tried it myself.

  3. andré says:

    So to catch fire in potassium chloride it has to be finely ground to stay and then it is mixed with the powder dye color, and have to grind the powder color dye to be able to mix with the potassium chloride and need to mix sodium bicarbonate to delay combustion, and burn more slowly?

  4. Reggie says:

    How touchy is the potassium chlorate? Could you ball mill the smoke mix after combining with the chlorate?

  5. Chike says:

    I’m glad I read the above article. When it didn’t light, I added more chlorate, which sputtered. I thought about particle size, but wrongly thought that a smaller size, would cause it to burn to fast and detonate. Thanks for the tip.

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