Guest Post by Charles A. Speer
We have been working on a method to create replicas of artifacts that we can perform experiments on; such as reducing a stone tool preform into its final shape, be it a projectile point, knife, scraper, etc.. In order to accomplish this we have developed a proof of concept method that we hope to expand into many areas of research in the future for the Department of Anthropology at Texas State, the Center for Archaeological Studies (CAS), and the Prehistory Research Project (PRP).
In order to create replicas that we can treat like real stone artifacts we have to use several instruments. First, we use a FARO Edge 3D laser scanner that can capture details as fine as 25 microns (about 0.001 inch) of the artifact we want to replicate. We then print out a 3D model using the information recovered from the 3D scan. We print out the 3D model in a photopolymer using a Stratasys Objet 500 Connex3 3D printer. We print out the model at around 117% larger size than the original artifact. We do this because the porcelain clay we use to cast the final replica in, shrinks as it dries and is fired in a kiln. To get to that stage, we take the 3D printed model and make a mold out of it in plaster. The plaster captures even the finest details of the 3D printed model. After the plaster mold has fully cured, we then fill the plaster mold with porcelain slip (liquid clay) and let the cast dry. After the casts are completely dry, we fire them in a kiln and they are then ready to study and carry out experiments on.
The reason we use porcelain as the casting material is because it has all of the same properties of stone used in the production of stone tools, also known as knapping. The porcelain replicas allow us to see insight into the skill level of individuals as well as the morphology of flakes created by certain techniques in stone tool production. We can create as many replicas as we need for each experiment. We can also stop an experiment at a certain stage and make replicas of that point in time to try different methods or techniques in knapping. We can then analyze all of the debris, or debitage, from knapping and make correlations with the debitage we see in the archaeological record. We hope that this method we’ve created can answer many questions in stone tool production.
Charles A. Speer is a post-doctoral research associate at the Prehistory Research Project (PRP) at Texas State University.