How Explosives Work

How Explosives Work

Explosives are chemicals and, like all chemicals, should be treated safely and with respect.

Unlike other chemicals, most explosives detonate rather than burn. A detonation is a very rapid chemical reaction using oxygen that is contained in the material rather than in the air. In a detonation, the chemical reaction releases gases that rapidly expand and give off energy as they become hot.

Two Basic Types

Explosives are categorized into two basic types, low explosives and high explosives. Low explosives tend to deflagrate, rather than detonate, which means that they burn at a slower rate and create less pressure than high explosives. Low explosives are often used as propellants to force a bullet out of a gun or send a rocket into space.

Low Explosives

For many years, black powder was the most common low explosive used throughout the world. But black powder, or gun powder as it was commonly called, produced a large amount of smoke and was dangerous to use. Today black powder is still used for pyrotechnics (fireworks), special effects, and other specialized work, but it has been replaced in commercial blasting by safer, more productive explosive materials.

High Explosives

High explosives create more pressure and burn more quickly, detonating almost instantaneously. The proper use of high explosives by today’s explosives engineer, produces minimal ground vibrations and air overpressure.

The first high explosive used in commercial blasting was nitroglycerine, also called "blasting oil." Nitroglycerine was dangerous to use because it is an unstable chemical. But in the late 1800’s, a Swedish chemist, named Alfred Nobel, invented dynamite by mixing nitroglycerine with a special clay, called kieselghur, and packed it into sticks.

Dynamite became the first safe high explosive used. It can be dropped, hit with a hammer or even burned and will not accidentally explode. There are a number of different types of dynamites being used today, all containing nitroglycerine.