MOLD RELEASE AGENTS

71kidcasper · #1 11-03-2006, 10:52 PM

I have just finished building to molds for the rear seats in my 71 20sf. I built the molds out of MDF, thanks Strick for all of your pictures, filleted all of the corners,apllied two coats of epoxy, sanded between coats and now I think I am ready to start laying up glass. My question is what is the difference between a liquid release like PVA poly vinyl alcohol and your typical paste style mold release? Also which one would be better for a one off mold or should I
use them in conjunction with each other? Like using the paste on the mold first and then spraying on the PVA. Additionally, if I should spray the PVA do I have to use a real spray gun, or is there some other method?

strick · #2 11-03-2006, 11:30 PM

I've never used the PVA so I cant comment on that but if your mold surface is smooth enough then all you need to do is wipe on the wax and buff. Repete this 3-4 times and thats it. I think the pros use PVA on molds that are going to be reused over and over again.

strick

71kidcasper · #3 11-14-2006, 07:44 PM

I waxed the inside of my molds four times buffing each time and allowed the final coat to dry one hour after buffing. Next I layed up all my layers of glass ,everything went pretty smooth. I precut all of the glass so not to be in a rush during layup. Put a heat lamp on the molds over night and hoped for the best for the next day. When I tried to extract the seats form the molds I had several spots that were stuck. They came apart and I will have to do some sanding to remove the pieces that got stuck. Did I somehow screwup what seemed to be a simple process or do some spots ocassionally stick.

strick · #4 11-16-2006, 12:32 PM

I'm not sure what went wrong. maybe you did not let the wax dry long enough? or you may have buffed it too hard? what kind of wax did you use? Partall seems to work good for me. what I do on the small stuff is just wipe it on nice and thick and let it dry then just lay up over the top of it. No Buffing. They pop out really easy. You will have to wipe the part with acetone after you get it out of the mold to get the wax off.

strick

71kidcasper · #5 11-16-2006, 08:19 PM

Hey Stick, If I am just going to wipe on a thick coat of partall, yes that is what I am using, do I need to coat the inside of the MDF mold with epoxy or will it work with just the partall? Sounds like I could save myself a lot of time by not coating and sanding. Thanks again for all of your pictures they have been alot of help.

gigolot · #6 11-17-2006, 12:45 AM

I Used masking tape on my forms, came off incredibly easy. Only problem is it wasn't completely flat because the tape was overlapped. But that is easily fixxed with some sanding.

strick · #7 11-17-2006, 02:31 AM

Quote:

Hey Stick, If I am just going to wipe on a thick coat of partall, yes that is what I am using, do I need to coat the inside of the MDF mold with epoxy or will it work with just the partall? Sounds like I could save myself a lot of time by not coating and sanding. Thanks again for all of your pictures they have been alot of help.

If you look at my thread on the 20sf the gunnel support molds were not coated with epoxy. They were factory primed MDF that is used for making household shelves. As long as the surface is somewhat smooth and you get enough wax on it it should come off OK.

strick

warthog5 · #8 11-17-2006, 12:14 PM

I use mold release wax. [3 coat's] Then I put PVA in a Prelaile sprayer and spray the mold lightly for 2 coat's.

I figure why take a chance. It has worked well for me.

Bigshrimpin · #9 11-17-2006, 04:18 PM

I second the PartAll wax . . . that stuff is great!

71kidcasper · #10 11-18-2006, 08:29 PM

I made a couple of molds for the rear seat hatches out of raw MDF. I used blue masking tape to create all of the inside corners and then wiped on a heavy coat of partall to the tape and the bare MDF. I put a couple of heat lamps on it for a couple of hours. Everything turned out great. What a time saver. The first two molds that I made were coated with two coats of epoxy and buffed four times with partall. They came out great also, but it took a couple of days to get them ready for glass. Thanks to everyone for their input. I will try to get some pictures posted when I figure out how. Strick offered to post them for me, but I just never sent them.