thinning epoxy for mould work.

[ChrisFeole]

I was a Toledo and talked to a guy who makes glass fusealages and other items. He said to use a pure Isopropyl alchohol to thin West Systems epoxy. I have used Denatured alcholol but the result was somewhat rubbery or not as hard as I would bave liked. Also should I use a heated curing box. Would this help in making the thinned epoxy harder upon being fully cured? Is there a better epoxy that is easier to work with? My items are still too heavy for my electric projects.

[planeman]

Your question about thinning epoxy is a good one. I have been thinking about this with the hope that I could buy epoxy by the pint at the hardware store and thin it to what I need.
I searched and found this from a manual:

http://www.raka.com/epoxyman.htm

EPOXY THINNING AND CLEAN-UP SOLVENTS : Acetone, lacquer thinner, and denatured alcohol are three common economical solvents that work well with epoxy. Denatured alcohol doesn't cut the epoxy quite as well as acetone, but is much safer if skin contact occurs. Generally it's not recommended to thin your epoxy with evaporating diluents because you may lose strength, waterproofness and have shrinkage. The curing process may also be affected. If you must add a local shop solvent, then denatured alcohol is a good choice (no more than 5%). It evaporates slower out of the cure than other solvents and its ability to mix with water may have some benefit, such as saturating rotten wood. The best way to thin epoxy without losing strength is to moderately heat the unmixed resin and hardener. Warm epoxy generally gives better results and if its possible try to heat the area to which you are applying the epoxy.

Obviously acetone and lacquer thinner are out for those of us working with polystyrene foam. Denatured alcohol is about all that is left.

I'll keep on searching.

Planeman

[SteveS]

Chris,

It should not be necessary to thin the epoxy for molding or wing layup. West, EZ Lam, P.J.'s etc are all pretty thin at room temperature. Although it's not a problem now, sometimes winter temperatures in the work room will drop below 70 degrees F. and you will see a thicker epoxy. If you attempt to work the layup below 70 F. there will be a lot more resin in the layup and the time needed to do the layup will increase a lot. If you feel the need to thin the epoxy mixture then 99% isopropyl alcohol is available at chemical supply houses.

For maximum strength and heat resistance you should definitely use a post cure heat box. Follow the directions for time and temperature, and if you're using carbon fiber cloth protect it from the heat of direct sunlight with white/reflective covering (primarily for CF D-box construction). The epoxy matrix will be harder and less likely to soften after a post cure heat treatment.

If your layups are too heavy then spread the resin farther or use teflon treated fiberglass with paper towels to wick the excess resin out during vacuum bagging. Weigh your cloth and mix the same weight of resin, try not to mix any extra and that will give you slightly less than a 1 : 1 ratio of resin to cloth. Stretch the resin by using a foam roller for application, saturate but no more. It should look dry. Forget all you hear about using a credit card to spread poured resin. You'll never get the excess out that way, and the excess resin does not make the layup stronger.

Good luck,
Steve Smith
Atlanta

[ChrisFeole]

Thanks for the info. I'm going to try to thin whith both and see if the post cure box does the trick. To date, I have not used the post cure box. thanks again.

[davidfee]

What Steve Smith said.

Yes, use a post-cure box... but be careful not to overheat (and warp) your molds.

Are you sure you need to thin the WEST epoxy? I can't imagine that it would be thick enough that it would need thinning. In a wet layup I usually use excess epoxy in the layup and then use lots of toilet paper/paper towels to blot away the excess.

I've never felt the need to thin my epoxy for mold work or bagged wing skins. If you use anything to thin the epoxy, make sure it doesn't also destroy your mold release. Alcohol, acetone, etc. will almost certainly dissolve your wax and PVA (if you use it)... which would make for an ugly scenario.

regards,
David

[ChrisFeole]

Are you saying you soak up the epoxy shortly after laying up your glass? Do you use west systems? It's all I have used so far.

[davidfee]

Are you saying you soak up the epoxy shortly after laying up your glass? Do you use west systems? It's all I have used so far.

Yes, I lay up the glass with extra epoxy and then blot the surface until it's as dry as I want. I do this because it's easier for me than to try to mix/apply the exact amount I want. The surface of the glass should not have a glossy "wet" look. I do the blotting before the epoxy starts to gel.

I don't use west systems, but I use Jeffco, which is about the same viscosity. I also use MGS which is more "watery."

Good luck,
David