Rubber mold basics

In order to give you some idea of the process involved in making a rubber or latex mold, here is a quick rundown.

Part 1 - The easy part, decide what it is you want to copy or make your mold of and get one.

Part 2 - This is the long part. It could take 5 or 6 days if you are only able to paint a couple of times a day.  You cover your original - lets say it is a frog - with release agent.  You may not always have to do this.  Some plastics and resins do not need it.
Now paint the frog with the rubber paint.  Let it sit untill it is almost dry - you can put your finger on it and no paint sticks to your finger.  Paint it again and again. Do this until you have built up a thickness of about 3/16" or so.  You can judge this by painting a piece of wood or something every time you apply a coat to the frog.  Look at the wood to see how thick your test paint is.

Part 3 - After the paint has dried for 2 or 3 days you can start to make the support for the rubber mold.  If you can picture the mold as a rubber glove, when you fill the glove with water it will stretch.  You have to stop the stretch.  Most of the time this is done with a fiberglass case or backing that you will make to go over the mold.  You may have to make this case in 2-3-4-5 or more pieces that will bolt together.  This is so you can take the case off easily.  If there are a lot of undercuts in your frog then chances are your case will be several pieces.
You can avoid having a lot of pieces by filling undercuts on the outside of your frog before you start to make the case.  This means more time painting on the rubber paint.  This is a good thing because the fewer pieces in the case the easier it is to use.
When you make your case it has to have a good big base, it will be holding the rubber mold upright when you fill it with concrete.  You don't want it to fall over just when you get to the top! 

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