I am trying to duplicate a cowl. I made a mold with PP OK but when I tried to make the product I used paste wax for a parting agent and the polyester resin did not set up where it contacted the wax.
What do you use as a parting agent?
What can I use to clean the mess out of the mold? I tried alcohol but I didn't have much success.

Acetone will clean the resin out, but I am not sure what it will do to the plaster.

Acetone shouldn't hurt plaster... the acetone being organic solvent and the plaster being ionic stuff. You can always try it on an outside surface to be sure.

dirtybird, check out the carbon fiber forum. you will get more information about mold making , parting agents, and gust about any other question you could possibly come up with. Ive litterly spent days reading on the same problems your haveing. Good luck and happy flying.

Did the paste wax have a silicone additive because that will tend to inhibit the curing process of polyester resin and leave it tacky. If you check out the Fibreglast website, they have a mold release paste wax by Partall that is silicone free. They also have what most people use as a release agent...PVA or aka PolyVinyl Alcohol. Usually sprayed on right from the bottle without diluting and at a higher pressure than what you would use to spray paint. Usually about 3 or 4 coats one after the other (it dries quite quickly).

As for the plaster mold, it would have been a good idea to use something as a seal coating on it like perhaps some form of primer coat, like a catalyzed primer. Something to seal the plaster and give you something to sand down to a finer finish. Also, I think the plaster would absorb that PVA and you would need to use the wax first to prevent the PVA from soaking in too much and not working as a parting film.

Check out the Fibreglast website at http://www.fibreglast.com/ to see what is available. Good luck and good flying.

Thanks for the replies. I used Turtle wax I got from the supermarket. I guess it has silicon in it and that was the problem. I will have to start over and use some other wax. Someone suggested I use Pledge. I think I will look for a local fiberglas shop and get the proper ingrediants or order them from the internet.

Dirt.....

Way back when, I did a few model boat hulls using plaster of Paris for the molds. Found right away, I had to sit outside for two weeks, in the summer sun to dry out good. Then painted the inside with some sort of enamel paint. Put four coats in there too.

Used floor (paste) wax of unknown brand. Has Carnuba in it.

Then went through the laying up process.

I used a P-P mold as it would not react with the plastic plug of which I wanted to copy. Anything else got warm and distorted the original.

Wm.