Mold release

I just made a new fin mold. I used TR high temp mold release wax. I put 6 or 7 coats of wax on the plug as per the instructions and laid up the mold using 1 lay of .75 oz cloth and 5 lays of 1.5 oz matt. It stuck like sh*t to a blanket! I’ve done the same procedure using Oscar’s wax with no problems. Any ideas what I did wrong?

Hi Don, I’ve got that tee-shirt buddy and now I use wax as “blocking” agent and PVA as “release” agent as I’ve have found sometimes there appears to be chemical reactivity between the mould surface and the resin which wax was unable to block and PVA was the answer.

Really don’t know what the cause is ? but I believe warming wax-up so that it semi flows on has helped and only buff it once each coated has dried (approx. 30 mins) Have heard different paints and primers under the wax have had reactions to wax, but nothing conclusive. The few times I have not used PVA it has either worked only after laminating 24hrs after final wax coat, any time earlier and it has been a problem for me.

Found this article on the web, may help provide answers

Cheers Alan

Thanks for that link Alan
I think that explains it in a way that I can accept. I have recently stopped using PVA in most stuff but I always chickened out and used it on the first pull. This is the first time I didn’t use it on the first pull. I didn’t realize that until I read that article and then the light went on. I’m wondering now if just coating the plug with PVA for a couple of days would accomplish the same as a test pull. The article was about polyester and that’s what I was using. I use poly for molds. Epoxy for boats. I use un-waxed resin and I’m always impatient. I’m thinking that popping the part off early would leave all those grabby polyester molecules just waiting. Putting a coat of PVA on would seal it up and allow them to cure in an airtight spot.
Proceeding with extra, extra caution

Know that impatient feeling …I get burnt every time :slight_smile:

Here something interesting … Hairspray !!! but I won’t be the test dummy on this one :smgreen:

Note: Test first:- Keep in mind that PVA is normally applied over waxed surfaces and is not particularly effective as a mold release on its own.

I was wondering about these new hydrophobic coatings. Has anyone tried them?

I have fooled with the hydrophobic coating a bit, but not as a mold release.

Check the composite forums at
for some great info on mold releases, both for plugs and molds.

For a fin mold, if the plug is exactly the shape and thickness you want, using a spray coat of PVA will alter that…slightly. Of course if you use PVA to make the mold, AND PVA to make each pull, I think you are back to the original plug size, assuming you can get the two mold halves to bolt together on their faces.

I don’t do much mold making anymore, but have used the Freecote products with good success. Also, most people recommend painting your plug with 2K paint as a final step before moldmaking. Some other paints can react even with wax and even PVA.

Hi Hew565,

Ive had issues even with 2 pack paint. The only way I’m assured of no sticking is to finish the mold/plug with plain/coloured epoxy and wax that. I have a mate who swears by Dubbin polish as a mold release.


Just for info:
It happen to read the technical notices of several waxes.
Often the manufacturers mentioned that their waxes are uncompatible with polyurethane painted surfaces.
A french manufacture has developed a specific wax that it is compatible with polyurethane paint product.

Carnauba mold release wax works excellent.
5 coats wiped on lightly polished after allowing each coat to dry for 30 minutes.
Polish lightly not to cause too much friction heat or you’ll ruin your wax job.

I waxed bare alumin. as a fixture and laminated several layers of cloth with epoxy. To make a quick mounting bracket.
The brackets came away easily.

If you are at all serious and want to make molds for your hulls, keels and decks, may I suggest you visit the WEST Systems page and subscribe to their newsletter. The most recent one (with war canoe on cover) has an excellent article on the tests they have done for various release methods (including hair spray). For a few minutes of your time, it is a free, multi-page, multi-color booklet that provides hints and tips. If you haven’t subscribed, I would recommend you do it, and maybe ask if you can get the most current issue. I will see if they will allow me to scan and post with copyright credits to Gougeon and WEST Systems.


Thanks for the info Dick. Anyone can view the webpage or download the pdf. file Going to give the wax, hair spray a try.

You should have used PVA over the wax!!!

Just saw this:

i have been using partall #2 and pva… but to be honest after 4 parts have been pulled i only use 1 coat of wax. seems you can build up a layer of wax every time you pull a part…
so 6 coats of partall buff out and 2 coats or pva… and nothing will stick