Bubbles or 'void spaces' collapse under the high-pressure shock waves of an explosion.
Compression instantly forces up bubble temperature and ignites the surrounding material.
More and more bubbles get converted into these 'hot-spots' as shock waves rush through a detonating explosive. Only bubbles below a certain size produce enough heat to drive an explosion forward, he adds. Explosives are given void spaces by filling them with porous solid bits. Tiny glass balloons, mineral particles and even pieces of corn all put crushable air pockets into the liquid. From the size and number of these additions, manufacturers can calculate how many void spaces, on average, a liquid explosive contains.