Black snakes, sometimes called glow worms, are small tablets that you light, using a punk or a lighter, that burn to produce long black 'snakes' of ash. They produce some smoke (which had a characteristic, probably toxic odor), but no fire or explosion. The original fireworks used to contain salts of a heavy metal (such as mercury), so while they were marketed for kids to play with, they really weren't that much safer than conventional fireworks, just dangerous in a different way.

However, there is a safe way to make black snakes. You can heat baking soda (sodium bicarbonate) with sugar (sucrose) to produce carbon dioxide gas that puffs up black carbon ash (see a video).

Soda & Sugar Black Snake Materials

• sand
• alcohol or fuel oil (I didn't have any high-proof alcohol on hand, so I used lighter fluid left over from the handheld fireballs project)
• baking soda
• sugar (I used powdered sugar, but you can grind table sugar in a coffee grinder)

Make Snakes

• Mix 4 parts powdered sugar with 1 part baking soda. (I used 4 tsp sugar and 1 tsp baking soda.)
• Make a mound with the sand. Push a depression into the middle of the sand.
• Pour the alcohol or other fuel into the sand to wet it.
• Pour the sugar and soda mixture into the depression.
• Ignite the mound, using a lighter or match.

At first, you'll get a flame and some small scattered blackened balls. Once the reaction gets going, the carbon dioxide will puff up the carbonate into the continuously extruded 'snake'. Actually, you don't even need the sand.

I tried this project using baking soda and sugar in a metal mixing bowl, added the fuel, and lit the mixture. It worked fine. The old firework snakes had a distinct smell. These have a smell too... burnt marshmallows! If you use pure ethanol, sugar, and baking soda, then there is nothing toxic about this project. One caution: Don't add fuel to the burning snake, since you risk igniting the alcohol stream.

How Black Snakes Work

The sugar and baking soda snake proceeds according to the following chemical reactions, where sodium bicarbonate breaks down into sodium carbonate, water vapor, and carbon dioxide gas while burning the sugar in oxygen produces water vapor and carbon dioxide gas. The snake is carbonate with black carbon particles:

 

2 NaHCO₃ ? Na₂CO₃ + H₂O + CO₂

C₂H₅OH + 3 O₂ ? 2 CO₂ + 3 H₂O

These instructions were adapted from a tutorial given on Boing Boing which in turn came from a defunct Russian site. The Russian site suggested two additional ways to make chemical snakes:

Ammonium Nitrate Black Snake

This works the same way as the sugar and baking soda snake, except you use ammonium nitrate (niter) instead of sugar. Mix one part ammonium nitrate and one part baking soda. This recipe is more like what you would see in commercial black snake fireworks, which are supposedly composed of soda with nitrated naphthalenes and linseed oil. It's another very safe demonstration, though not safe enough to eat, like sugar and baking soda.

Ammonium Dichromate Green Snake

The green snake is a variation on the ammonium dichromate volcano. The volcano is a cool chemistry demonstration (orange sparks, green ash, smoke), but it's a chemistry-lab-only demonstration (not safe for kids at all) because the chromium compound is toxic. The green soda snakes are made from:

• two parts of ammonium nitrate
• one part of powdered sugar
• one part of ammonium dichromate

Mix the ingredients, add a small amount of water, and roll the result into a snake shape (gloves please!). Allow the snake to dry (the tutorial suggests using a hairdryer to speed the process). Light one end of the snake. In this case, an orange snake burns to green ash. It's worth knowing how to do this demonstration if you have ammonium dichromate and ammonium nitrate on hand, otherwise let the Russian photos suffice and play with the sugar and baking soda snakes instead. Another (spectacular) form of black carbon snake results from reacting sugar and sulfuric acid.