Polyester resins for Plaster Subjects

[allen381b]

This is my first posting as a new member. I am writing about a problem before I formally make an introduction but expect to do that as soon as I have a moment to present myself. May I ask the question though? Most of my work is in various exotic woods. After having prepared negative moulds from several pieces in wood in order to produce a number of positive wax forms for bronzing, I am wanting to do some larger subjects in plaster but they need to be very strong when cured. I read about polypropylene resin as a strengthening bond for plaster but could not find it and especially in larger quantities (10-20 lbs).. As a derivative of polyester resin, I believe, would this latter--polyester--do the job? I know where to get the polyester.Thank you for any of your ideas. Allen

[Merlion]

Do you mean you'd like to have plaster casts that would not break easily? I've never heard of adding polyester resin to plaster to strengthen it, unless you mean fiberglass which is glass. We do add fiberglass to plaster for this purpose.

[Arrow]

Acrylic additive. Never used it so I can't vouch for it.
http://www.fxsupply.com/materials/padd.html

FMG uses some kind of acrylic mix.
http://www.ball-consulting-ltd.com/fortonmg.asp


WEP might work as a additive too. Since it is already formulated to mix with water in the first place.

WEP: Water Extended Polyester. Page 74
http://www.iasco-tesco.com/cat55/index.htm

[Landseer]

Acrylic additive. Never used it so I can't vouch for it.
http://www.fxsupply.com/materials/padd.html
It says you can use this in PLACE OF water, it's $40 a gallon + shipping so that could get mighty expensive doing THAT!
Many of my casts in hydrocal take around 5-6 quarts of water, if I substituted this for the water it would be way too expensive.

It doesn't say how much to use to get some kind of effect.

[halfbad]

I think the reference to polypropylene was made as a fibrous material that would be used as a reinforcement in the plaster-much like fiberglass in polyester resin or steel in cement. You can incorporate the fibers into the plaster and increase the flexural strength, which plaster does not have much of. But you may be better off just going to a stronger type of gypsum like Hydrocal or even FGR-95 along with either the poly fibers or fiberglass for maximum effect.

[Lunarburn]

Here is a product that i have used in the past.

http://www.pinkhouse.com/Forton.html

It is a latex additive to plaster, so alot less toxic then polyester resins. You apply a few face coats then back it up with several layers of fiberglass/forton.

I been able to cast life size figures with amazing detail that only weigh 50lbs or so.

[justme]

Hi,
I've worked with polyester resins with some difficulty. Have you heard of Forton? It is a gypsum/plaster composite that is very strong and delightfully easy to work with. It also takes paint beautifully.
j

[fused]

Forton MG (http://www.pinkhouse.com/Forton.html) sounds like a good choice (http://www.artmolds.com/gateway/technique/forton_1.htm) and there are a lot of sources (http://www.google.com/search?hl=en&lr=&q=Forton+MG&btnG=Search).