Previous research by the Bureau of Mines determined the probability of spark ignition versus current in methane-air atmospheres with a high degree of statistical confidence. However, all of these measurements were obtained using tungsten and cadmium electrodes as specified in Underwriters Laboratories Standard UL913, a national intrinsic safety standard. In the realistic mining environments, spark ignitions rarely occur between tungsten and cadmium components. Information defining the spark ignition probability of other more common materials is of far more value. The Bureau's Pittsburgh Research Center is currently engaged in research to estimate the spark ignition probabilities associated with more commonly used materials such as copper, cold-rolled and stainless steel, brass, tin, aluminum, and lead in a standard breakflash apparatus. By comparing the currents which give the same probability of spark ignition, the relative safety factor associated with each material can be more precisely estimated. The work and findings to date are summarized in this paper.