Bonding the Alginate to the Mother Mold

 The next casting was devised to attempt a solution to the problem of keeping the mother mold and the alginate together after they are removed from the model.  For this project we used my knee as a model.

John and I figured that we needed this to be worked out for a couple of reasons.  For one, we did not want the rigid shell to deform the alginate mold.  This happened a bit in our previous casting, when we were unable to get the alginate and the mother mold to fit back together perfectly.  We also struggled with alginate flopping over as it climbed the side walls of the mold shell.  We tried to pin them up while casting, but felt it would be better if the sidewalls were completely bonded.  To lock the alginate and the plaster shell together we used strips of burlap.  While the alginate was not yet set, we placed the burlap halfway into the mold material's surface.  Once set it was really locked into the alginate, and the plaster shell would reliably bond to the other side of the burlap.  It worked.  We had a nice mother mold that was well bonded to the alginate.  There are applications where being able to remove the mold from the mother mold would be desired, but for now our experiment was a success.  We did have a hiccup in that the alginate was very thin, and its surface was disturbed by the warp and weft of the burlap.  The final cast had some very nice skin detail, but there was a visible pattern from the burlap as well.  Next time we will have to make sure that the alginate is very thick, so that the print side of the alginate mold (the part that is formed against the body) will not be disturbed.

We tried casting with Hydrocal FGR again.  Still works much thinner than Plaster of Paris, but we are getting better.  This time we decided on a very thin layer, followed by a thin layer of burlap, and then one more thin layer of plaster.  We ended up with a very light and strong shell for the casting.  Really promising if we are going to scale this up.