Propagation of a burning front over a condensed material from a focus

Measured propagation speeds are given for the combustion front in a blind gap in a condensed substance, which are related to gap height and mean pressure. The front may propagate monotonically, which is characteristic of relatively high pressures and wide gaps, or as a result of additional burning foci arising at a certain distance from the main front. At low pressures and particularly with small gap heights, the front propagates in an unstable fashion over the surface.