Part 4 - Take the rubber off the original.  Be careful!  It will be inside-out.  Now you can sprinkle a little talc on it and turn it inside-in.  Put it into the fiberglass case you made, bolt or clamp the case closed, invert the case so that it is sitting on that big base we where talking about.  Mix your concrete and fill the mold.  Let it sit to cure for a couple of days.  This is the test run for this mold and case so you want the concrete extra hard when you do your first de-mold.

Part 5 - Unbolt the case and take out your casting.  Carefully take the rubber mold off the casting.  If you are a skilled mold maker it should be right the first time!!  If not you need to look at any problem areas and decide what you can do to correct them.

Now you can see why the rubber or latex molds cost so much and why they take a couple of weeks or more to make.  There is a lot more information on this at The Hypertufa News if you are interested.  They are a great source that I reccomend to everyone.  You can also try Hypertufa Projects.

The building time can be shortened by using fast drying silicone based rubber, it is a little more expensive but....  Plaster can be used instead of fiberglass if the mold is not going to be used a lot.  This is cheaper but not nearly as good as fiberglass.

My thought is that for a person to start into the casting business the best way is to start with a few plastic molds - no fiberglass backing needed - do a few pours and see if you want to keep at it. If you decide you do, then as your skills increase, start to think about investing in a simple latex mold.  You may be able to find a used one in good shape.  Try it and see if you want to do that type of casting.

The results are great once you have mastered the process but it is not a cheap or easy thing to do as a novice.

SEER