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It's easy to make a smoke bomb and actually pretty safe, but I realize when you read about projects online it's hard to tell which ones are safe as in "you probably won't die or poison yourself" and which fall into the category of "I'd let me own kids do this". I would let my teenage sons make smoke bombs with adult supervision. What are some safety considerations of the project? This email covers the important questions:

Dear Anne:

My 13-yr old son wants to make a homemade smoke bomb (with adult supervision). Your instructions seem to be the most detailed and thorough. But before conducting this home chemistry experiment, I want to be sure this can be done safely.

What are the risks/potential dangers associated with this procedure?

Is there any risk of the smoke bomb exploding, or igniting rapidly? Under what circumstances?

What should should we watch out for?

Also, where is the best place to buy a small quantity of potassium nitrate? Is it still available at most garden stores? Some stump removers use other chemicals; and some don’t list ingredients at all.

Any advice most appreciated!

Tom S.
Chevy Chase, MD

Smoke bombs are made by reacting potassium nitrate (saltpeter) with sugar over low burner heat. The project won't harm your cookware, plus the ingredients are safe enough that you can use the dishes you would use for eating, as long as you clean them. The MSDS for potassium nitrate provides handling and safety details, but I'll summarize the relevant points. Though potassium nitrate is found in some foods, you don't want to eat the pure powder. It's reactive, so it will cause itching and/or burning if you inhale any or get it on your skin. Potassium nitrate should be stored away from heat or flame. The chemical isn't flammable, but it's extremely reactive. Heat promotes reactions, which you don't want occurring on a shelf in your garage, for example. Follow the safety instructions on the container. If you get it on your skin, immediately rinse it off with water. If you spill potassium nitrate on the counter while making the smoke bomb, wipe it off with water.

You want good ventilation while heating the ingredients, as from a vented fan. An outdoor stove would be a good option. The big thing to watch for is spilling the mixture on the burner because it will catch on fire and smoke. If that happens, you'll get a lot of smoke and probably set off your smoke alarm. The smoke itself is no more or less dangerous than wood smoke, which means you don't want to take deep breaths of it. Ignite the smoke bomb outdoors. I can't envision a scenario where it would be possible to cause the smoke bomb to explode. How much flame you get depends on the potassium nitrate to sugar ratio. You can go from a smoky blob that will barely burn to a fast-burning fiery smoke bomb. If you set the smoke bomb on a combustible surface (like dried leaves), it could start a fire. If you need to put out the smoke bomb, you can douse it with water.

The hardest part about making a smoke bomb is finding the potassium nitrate. In some places, it may be sold next to epsom salts in the pharmacy section of a store. It is found in some garden supply centers as a fertilizer. It is sold as a food preservative for making salted meats. If you're highly motivated and have some time, you could even prepare it yourself. However, it's probably easiest to buy a small quantity online (e.g., Sargent-Welch). Supposedly some Indian food stores sell it as an ingredient named Kala Nimak. If you're in the UK, there is a forum discussion listing places that offer potassium nitrate. It's harder to find than in the past, not so much because it can be used to make gunpowder as because better products are available for most applications.

Make a Smoke Bomb | Make Green Fire
Photo: Homemade smoke bomb. (Timo Halén)
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January 15, 2008 at 6:59 pm
(1) trr says:

I made a mixture of molten sugar and potassium nitrate on the stovetop when I was a teenager and put it in a container and let it harden. I remember it making more than smoke though. Once I got it lit, it made a flame several feet high and burned a pretty good hole in the grass underneath. It was good clean fun.

January 21, 2008 at 4:50 pm
(2) noname says:

i should try this!

July 26, 2011 at 12:44 am
(3) momo says:

it realy awesme

July 3, 2008 at 11:01 pm
(4) Nick says:

I made a smoke bomb tonight but i used a old tomato sauce can and while i was making it something happended to set the whole thing off, it made my whole kitchen smokey and you couldn’t see a thing it didnt smell and was harmless but i got in so much trouble, i recomend not doing this inside do it on a barbaque or potable stove outside.

March 17, 2009 at 11:35 pm
(5) Anon says:

Lol @ Nick. Kids, this is clean fun but let your parents know before you try anything.

July 26, 2011 at 12:47 am
(6) momo says:

is it safe for a science fair

November 9, 2011 at 7:46 am
(7) First Aider says:

My 17yo neighbour liked to make smoke bombs like this. He made one this afternoon with no problems – then when heating up a 2nd batch – it unexpectedly lit up while still in the pan. He got many BURNS on his legs & arm – that quickly developed into blisters & were VERY PAINFUL. He got some blisters between his toes – so he CAN’T WALK. This is despite correct burns treatment – putting it under cold running water & then to hospital. He vows he NEVER wants to make one again. It is NOT SAFE!!!

November 26, 2011 at 10:57 pm
(8) timsta says:

yo neighbors a moron. Let me also guess that you weren’t there and have NO IDEA WHAT HAPPENED!!! He might have used a different recipe or spilled it a little on a gas or fire stove. It doesn’t take much to ignite and how did he get burned? this isn’t f- ing gunpowder it doesn’t burn that fast or have the flames tall enough to burn you, his face would have to be in the pan to get bad enough burns to go to the hospital. Don’t ruin everyones fun pu55y.

July 5, 2012 at 9:16 am
(9) Lethal babe says:

This thing is safe until you make large batches, just tried making one yesterday and kitchen caught on fire with tons of marks on flooring, ceiling, and countertop. Overall, just be safe and don’t spill this stuff on the stove or you will definently have the fire department coming and a ruined kitchen for like ever. But this stuff is pretty cool, i made three other batches before and one of them made a soup heat up to a sizzling red color, so just be safe and smart.

July 28, 2012 at 1:59 pm
(10) i tried it says:

i made a smoke bomb , pottasium + sugar on low heat and a spoon of baking soda as shown here http://www.youtube.com/watch?v=Zdo2m0-o7Oo
after i done, i filled it into a paper tube , waited a hour and tried to light it . the mixture was very hard was very difficult to light it up , then my brother lighted it some how and it started to fire like rocket fuel fortunately its only burned my brother hand a bit . please reply why it happened because i made the same before that and all worked good

January 24, 2013 at 8:27 pm
(11) Jack Eagan says:

This is safe however I would not use a gas burner. Get a cheap electric burner for $20 at target. This way there is no open flame and precise heat control far below the flashpoint of the sugar saltpetre mix. Also do this outside in an area with nothing less then 5ft above it. And remember to make small batches.
Stay Safe

March 17, 2013 at 10:11 pm
(12) Lara lalemi says:

Quick question do you have to use a pan and stove? I want to do this at school in a lab. Can I use a beaker and Bunsen burner instead?

April 9, 2013 at 8:48 pm
(13) Connor says:

I wouldn’t ever recommend doing this at school. If the smallest bit reacts then you’re in big trouble. Fire alarms will go off and your school is going to be smokey for awhile. I’m not a lawyer or anything but there may be a possibility of the school suing. Don’t try it at school. There are many other places to show your friends but school is not one.

May 15, 2013 at 12:26 am
(14) Tracerhead says:

There I a mixture that doesn’t require any cooking.60 grams spectacide stump remover(100% potassium nitrate found in Wal-Mart gardening section) 40 grams sugar mixed together and then mixed into 30 grams of melted paraffin wax(in canning supply or with the jello in Wal-Mart). Should be the consistency of a slushy. Put in container and let dry for anywhere from 2hrs to 9 hrs. Fuse is helpful in lighting it. Just cannibalize some old fireworks and add that powder into it for easier light. Produces some flame. Have fun. Lots of smoke. Light somewhere without grass or flammables or have a shovel and water handy.

August 20, 2013 at 3:13 am
(15) tristan foyle says:

Smoke bombs aren’t as safe as they appear. Some sites call for baking soda to be added, but this can cause combustion while being cooked. I had this happen and it destroyed the kitchen.
Also when extinguishing smoke bombs be at a safe distance if you put them out. Water can cause them to explode.
And always wear protective goggles. I’m not an overly safe person but this is a must.

August 20, 2013 at 9:33 am
(16) Easy says:

You said that it is sometimes sold as fertilizer which I think might be incorrect. I know it’s sold as stump remover so I’m not sure if it could be used as a fertilizer. But I could be wrong.

October 5, 2013 at 4:54 pm
(17) Tong says:

I made some when I was younger, and when they say a low flame, they mean a LOW flame, even on a gas cooker the lowest setting triggered ignition and potassium nitrate burns at a high temperature, it went through the pan and the enamel on the cooker, let alone filling the house with thick white smoke. I recommend heating the sugar alone first, and removing from the heat before mixing in the potash and pouring into container.

Potassium nitrate is sold as a fertilizer, potassium is used by plants to harden the roots and open wounds from pruning to protect them from winter frosts.

February 25, 2014 at 11:17 am
(18) David says:

Lets be fair anything that melts glass cant be considerd safe. However teaching children to take the correct precausions is more important that preventing them from learning about science.

I have done KN03 experiments with my 7 year old daughter. We tested KN03 sugar mixtures to find which burned the fastest.

We then made a rocket out the fastest mixture by compressing the mixture with a hammer into a pipe and capping the two ends with clay then drilled a hole through the bottom up the centre of the compressed mixture. made fins and a pointy nose which we painted.

made fuses by mixing hot water with the mixture untill it was a paste and soaking absorbant string with it then left them to dry.

we made the smoke bombs (outside with a camping stove) for around the lanch site. we found that if we kept the mixture contained by using cuts of scafolding poles capped again with clay at one end the mixture had a slower burn. we also added baking soda and tried one with green packed tightly at the top.

we tried adding littlle bits of copper to see if we could get a green flame but it never worked.

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