After lighting the small tablet, the Novelty firework starts smoking and approx. a 2-foot snake of ash is expelled. They stay on the ground and do not emit sparks, flares, any form of projectiles, or any sound. They do emit a yellowish smoke. Black snakes are impressive and very safe, providing they are lit away from flammable material, thus making them especially suitable for young children. Their low price also makes them popular.
Sodium bicarbonate which produces carbon dioxide gas and sugar forming carbon containing ash, are common chemicals used for this kind of firework. Other sources report the contents as "a nitrated mixture of linseed oil and naphthalenes. "The traditional mercury salts are no longer used because of the toxicity.