The classic smoke bomb is a great project for the home or lab, producing lots of safe smoke, with purple flames. If you get dye and consider the shape of your creation, you can make a smoke bomb that billows clouds of brightly-colored smoke. Adult supervision is required.

Colored Smoke Bomb Materials

60 g (3 tablespoons) potassium nitrate (sold as saltpeter in garden supply shops)

40 g (2 tablespoons) sugar

1 teaspoon baking soda

60 g (3 tablespoons) powdered organic dye (such as synthetic indigo or an aniline-based dye, found in some craft & hobby shops; not common water-based dye)

Cardboard tube (best is an iced push-pop tube (eat the treat first), or you could use a toilet paper roll or section of paper towel tube, or even a rolled/taped paper tube)

Duct tape

Pen or pencil

Firework fuse (hardware, rocketry, construction, or hobby shops, or scavenge it from a firework)

Cotton balls

Saucepan

Make the Colored Smoke Bomb Mixture

Mix 60 g potassium nitrate with 40 g sugar in a saucepan over low heat. It's a 3:2 ratio, so if you don't have grams, use three large spoonfuls of potassium nitrate and two large spoonfuls of sugar (3 tablespoons and 2 tablespoons, if you feel the need to be precise). The sugar will carmelize and brown. Stir the mixture continuously until it resembles smooth peanut butter. Remove the mixture from heat. Stir in a spoonful of baking soda (a rounded teaspoon is fine). The baking soda is added to slow down the combustion when the smoke bomb is ignited. Add three large spoonfuls (3 tablespoons) of powdered organic dye. Blue dye and orange dye are said to produce better results than the other colors. Stir to mix well. Construct the smoke bomb while the mixture is still hot and pliable.

Assemble the Smoke Bomb

Fill a cardboard tube with the warm smoke bomb mixture. Push a pen or pencil down into the center of the mix (doesn't have to be all the way to the bottom but should be enough that the pen stands in the mixture). You could use a different shape, but the cylinder works really well. Let the mixture harden (about an hour). Remove the pen. Insert a firework fuse. Push pieces of cotton balls into the hole to tamp the fuse securely inside the smoke bomb. Be sure there is fuse left outside of the tube so that you will be able to light your smoke bomb. Wrap the smoke bomb with duct tape. Cover the top and bottom of the tube, too, but leave the hole area with the cotton and fuse uncovered. Go outside and light your smoke bomb!

Tips for Success

The key to producing vibrant colored smoke is using an appropriate dye. The color is produced by vaporizing a dye from the heat of the smoke bomb, not from burning a pigment, which always produces normal smoke.

Getting a good display also depends on the geometry of the smoke bomb. When the dye is vaporized, the pressure from combustion forces it out to produce the smoke. There needs to be enough pressure inside the smoke bomb to push the smoke out, but not too much pressure or else it will burst. This is why cardboard and tape are used. You can control the opening for the smoke. The materials are strong enough to contain a certain level of force but will rupture rather than explode if the pressure is too great.