A Northern Water Snake (Nerodia s. sipedon) model is located on a fallen log in the Shoreline diorama. Light can be seen between the snake and the log, which immediately destroys any illusion of reality. This has bothered me for many years. I initially thought that the model had been jostled from its position on the log and that I only needed to fiddle with it enough to get it back into its correct orientation. I made several unsuccessful attempts to reposition it and finally realized that the cast had distorted over time making a good fit impossible. I decided the only way to fix this problem was to cast a new snake.
The model was made in the 1940’s from an actual Northern Water Snake. The snake was collected, euthanized, and put in position on the log. This may have been tricky and pins may have been used to keep the lifeless snake hugging the log. A plaster mold was made over the snake and log. When the plaster had set, the snake was removed. The plaster was dried and liquid latex rubber was slushed into the mold and the excess poured out. The rubber was left to dry and another layer was poured in. Layer after layer was added into the mold to make the final rubber cast. The latex cast was removed from the mold and then trimmed and painted with oil paint. Over the intervening 70 or so years the latex became hard and brittle and it distorted enough not to fit on the log.
I inherited several old plaster amphibian and reptile molds saved in my storage area when I took this job. Unfortunately, this particular water snake mold had not been saved. Since I couldn’t find the original plaster mold, I made a new silicone rubber mold of the latex cast. I generally use platinum-cured silicone rubber because it lasts longer in my mold archive than the tin-cured silicone. Platinum silicone is slightly more expensive and is more easily inhibited by other substances with which it may come into contact. This proved to be the case with the latex snake. There was intermittent inhibition of the silicone over the body of the latex snake where uncured rubber was left behind. I’m not sure what caused this, but my guess would be that any contact with any of the old, exposed latex might have inhibited the silicone. The inhibition wasn’t extensive enough to redo the mold and I was able to get a passable cast in polyester resin. I chose polyester resin so I could heat the cast to make it pliable enough while hot to form fit to the log. Before I heated it, I drilled small nail holes over the body so I could nail it into place while it cooled.
After the cast was reformed to the log and cooled (it will now keep its new shape), I removed it from the log, cleaned up the cast, re-sculpting some of the areas marred by the inhibition, and painted the entire cast white to prepare it for final painting in oil paint. Greg Watkins-Colwell, the herpetology collections manager, provide an alcohol specimen from which to refer for painting. When it gets reinstalled, I will nail it onto the log just to be sure there will be no further distortion over time.