Abstract

This study was concerned with the effects of grit tempering upon the plasticity, texture, shrinkage and color of native southern Manitoba clay. Tempering material was obtained from friable granite collected from local archaeological sites. Clay tiles were formed with increasing amounts of temper (10% to 40%) and fired at a range of temperatures (500-900 degrees C). An inverse relationship was observed between the amont of tempering used and the plasticity, malleability, and possible surface finishes. It was noted that the dried and fired clays showed little difference in shrinkage between tempered and untempered clay. Tempering materials are usually added to reduce shrinkage but too much tempering weakens the clay. Prehistoric pottery of this region is often heavily grit tempered and the percentage of tempering used is higher than necessary for the clay used. Thus grit tempered pottery may reflect a cultural trait rather than a functional trait.