The objective of this study was to determine compositional variables that result in early reaction of aluminum in detonations of pressed high explosive compositions, defined as reaction by 7 volume expansions as measured by 2.54cm diameter copper cylinder expansion tests. In order to accomplish this in an economical fashion, statistical mixture design of experiments (DOE) was used in conjunction with anaerobic detonation calorimetry. The effect of binder type (e.g. energetic vs. inert), binder content, HMX content, aluminum content, and aluminum particle size was investigated. It was determined an energetic binder must be used to obtain significant aluminum reaction at volume expansions less than 7V/V-0. Aluminum particle size was only a minor factor. Furthermore, the compositional oxygen balance only provides a general indication of which compositions exhibit more aluminum reaction than others.