Friday, September 12, 2008

Moldy Things

Many model parts can be reproduced by using resin to make simple items in Room Temperature Vulcanizing Rubber RTV molds. It is not a difficult process and I will explain some of it today. This photo shows a typical product that has two parts A and B that are combined to make a mold, and a little bottle of mold release.

Smooth-on sells resin and rubber by mail and has excellent training information for those who are interested in using their products.

I like to make molds in special mold making plastic boxes. You can also make a mold box out of cardboard or even Lego bricks. These are re-usable and the molds slide out easily. Use rubber cement or white glue to affix your model part to the bottom of the mold box. The glue is just to hold it in place while the RTV hardens, it is not a permanent attachment. The model part should have at least 1/4 inch all the way around from the sides and at least that far from the rim of the top of the model box. Nearly any non-porous material may be cast but items with the fewest undercuts and without holes in them are the easiest.

Mix equal parts of A and B by volume and stir them until the RTV is a uniform color. Each part is a different color so you can easily tell when they are fully mixed up. Once the rubber is mixed up, pour it into the mold box and leave it for as long as the instructions say it takes to set up. Some are as quick as thirty minutes and some take overnight. When done, it will be very hard, like a car tire.

No comments: