> I've found this thread very interesting.I think I'll try a very simple
> approach to molding a custom seat.It seems to me that instead of using
> mortar mix,one could simply use wet sand, plaster and a few strips of
> burlap to produce a positive butt mold.This "butt track" is much
> (in most cases) smaller than some of the dinosaur tracks etc that have
> been cast with plaster and burlap.At least failure in this realm won't
> break the bank.Wish me luck.I'll report on my progress.

> darren

A bag of playground sand, and a bag of sand mix concrete are about the same cost -- usually about $3, but it could range anywhere from $2 to $5 at the local hardware home center. You would pay about $2.50 for 5 pounds of plaster.

Using both plaster and sand would be a bit more expensive, but probably not a wallet breaker.

But why bother with the plaster? If you are careful you can go down to the beach and just use a few buckets full of slightly damp sand, and sit in it carefully, get out of it carefully, and work from this. Sculpt the resulting creation, much as you might do with a sand castle.

You can carefully layup a layer of fiberglass and resin right on this. The underside will have some trapped sand, but so what? If you want to cut down on the trapped sand you might use a can of spray lacquer or cheap spray paint and put two or three coats of paint/lacquer on the pile of sand, as a weak barrier, before you put on the glass and resin.

Or, if you want a male mold, fill the sand pile with your plaster, or use a quick setting, expandable foam.

I think using loose sand is probably more trouble than it is worth. For the few bucks, get sand mix, which is basically sand and portland cement. Add water, stir, cover with a plastic bag and sit down. The weight is not a major issue.

When you are done with it, put it in the garden as a bird bath, or install a gnomon in the center, and use it as a sundial by painting hours around the edges of the depression. You need never tell the neighbors why it has that strangely familiar shape.

Hope this helps

Paul G. Jacobson