Stemming is best described as which of the following?

• A. Incombustible material used to confine explosives
• B. A color of the label
• C. A type of explosive
• D. A device used to ignite a fuse

Answer: (A)

Stemming is the inert, noncombustible material placed in a blast hole above the explosive charge to confine the detonation. This material seals the hole and traps the explosion’s gases, directing most of the energy into the surrounding rock, which improves fragmentation and helps prevent gases from escaping up the borehole or causing flyrock. Because stemming is defined by being incombustible and used to confine explosives, it matches the description of incombustible material used to confine explosives. It is not a color, not a type of explosive, and not a device used to ignite a fuse.