I am attempting to make a fiberglass mold for a school project and have been having a difficult time. I made a plug from the original metal part and applied several layers of rustoleum spray paint. After the paint was dry I color sanded and buffed the part until it was polished like a mirror. I then applied 7 coats of partall release wax. I ran into a problem when I started applying the tooling gelcoat. I decided to test the gelcoat on a small section of the mold first (ruined my last plug by just applying it to the whole thing) and within a minute of applying the gelcoat started to notice alligatoring (alligator skin?). I had this same problem before but assumed it was because it was too cold when I applied the gelcoat. This time it was around 70 degrees. It seems like the gelcoat eats right through the wax and begins reacting with the paint underneath. Do you think the problems are coming from the spray paint? I have seen others on here use spray paint to make plugs, but maybe I am using the wrong kind. Does anyone have any suggestions on what I can do?
The resin is reacting with the paint. Wax cannot block this no matter how coats you apply. The only way to remedy the problem with this paint and resin combination is to use a barrier coat of PVA on top of the wax.
I use a black catalyzed (2K) auto paint. My favorite is PPG Deltron DBC base coat with Deltron DC3000 clear-coat. I can’t confirm wether this works with just wax though. I does work with Frekote 770-nc semi-permanent system.
Another option is something like Duratec surfacing primer.
It’s always best to test everything on a sample before committing to the actual plug and mold.
Since you mentioned using this process on plugs, can you continue on with the process after applying the semi-perm? I’d like to know more about applying epoxy surface coat over semi-perm, and any tips or tricks pertaining to that. Also, I’m interested in what steps you take after the surface coat. Do you use cotton flocks and let it cure, then infuse similar to the process I’ve read on there, or some other process.
P.S. - As you mentioned on here in another thread, I switched from wax to semi-perm on my mold for making parts. The results are amazing. The part pulled so easy I almost laughed out loud. Previously I was using ~10 wedges and a lot of force. Now with the 770NC I used one wedge and barely pushed it under and the part pulled right out. Thanks for the tip!
I build all my molds using the Frekote FMS Sealer and the Frekote 770-nc release. I prep the plug with PPG Deltron DC3000 over the DBC base coat for color. I’ll polish this to mirror finish. I never polish molds. Polishing a plug is easier and faster.
I make my own surface coat using my chosen laminating/tooling epoxy resin and a fast hardener. I mix in 27% West System 404 High Density filler and 12% graphite powder by weight. I brush this first coat on rather thinly (dimensional), wait 10 minutes, and then zap it with a torch. The torch super heats the air bubbles and causes them to pop. I let this first coat tack up (tacky to touch but doesn’t transfer to finger). This I use the same resin and wet-out lengths of carbon tow. I work the tow into any tight corners with the tip of a small acid brush where fabric bridging can be an issue. I usually use 3 pieces of 12K in the corners. Then immediately I’ll brush on another application of the surface coat, wait 10 minutes, and zap it with a torch. I’ll then sprinkle this with cotton flock and blow off the excess. If the cotton flock seems to disappear I’ll sprinkle it again. I do this by putting some flock on a piece of screen. Then I just tap the screen to dispense the flock. At this point you can either stop and let it cure or continue with the reinforcement once the second application of surface coat has gone tacky. The flock will make for good secondary bonding if you decide to take a break. Depending on the part depth I’ll continue the process in the following ways.
If the part depth is rather thin then I’ll brush the surface coat with resin and then I’ll just mix Adtech EL-302-PC low shrinkage laminating epoxy and oven dried playground sand into a pourable slurry. I’ll pour this slurry over right over the plug so everything is nicely covered leaving a flat surface. The sand will sink and the excess resin will rise to the surface. There will also be a lot of bubbles that will rise to the surface. These can be simply popped with the torch. If you mold is small you can be done at this stage. If the mold is larger or requires more strength then I’ll use the excess resin to wet out around 30 ounces of glass. This goes really fast since the surface is now flat. Then I’ll mix up some sand and epoxy to a very stiff consistency and pack about 3/4" on top of the glass, then add 30 more ounces of glass. The glass weight and orientation should mirror the first layer of glass. The advantage is that this system poses no risk of fabric print-thru to the mold surface and the laminating is super easy since it’s performed on a flat surface. The downside is that these molds can be rather heavy and it requires a forming damn around the perimeter.
If the part is rather deep I brush the surface coat with fresh resin and start with some light 1 ounce glass on bias, then 2 ounce glass, then 3 ounce glass, then 6 ounce glass. I’ll often run a bead of resin/talc around any tight corners to prevent fabric bridging before applying the fabric. I want to vary the orientations of the layers between 0/90 and +/-45. I put down about 30 ounces of glass. Then I pack on 1/4" to 1" of dry epoxy/sand, Adtech EL-323 tooling compound if I want it lighter, or resin/Poraver if you want it lighter yet. Then I mirror the front layup onto the back of the tooling compound/sand/Poraver.
If the mold is really large you can infuse it with fabric and some layers of Soric to bulk the thickness.
i think you’ll find your problems are that the paint your moulding off is not cured enough… (i say that because its triping up within a minute)
or your gelcoat is not going off quick enough and therefore eating into the paint and making it tripe. (something else to watch out for, less likely)
pretty common problem.
solutions
you can get a really good release from primer gelcoat and usually mould off within 24 hours, but not much gloss.
2k paint is great for gloss to mould off but you really should let it cure in nice warm temp for 3 days. keep in mind if your leaving your part in cold whether it wont be curing at all.
can also ring manufacture and find out what there recommendations are re guarding the paint your using (often they dont have much idea thou ive found so its trial and error)
its really nice on a warm day if you can use 1.5 - 2% catylist and put it out in the sun straight after youve gelcoated.
if its not a good day i use a home made oven with a heater which gets the area up to 25 - 28 degrees celcius.
you can get a really good release from primer gelcoat and usually within 24 hours, but not much gloss.
2k paint is great for gloss to mould off but you really should let it cure in nice warm temp for 2 - 3 days. keep in mind if your leaving your part in cold whether it wont be curing at all.
I agree that partially cured paints on plugs can be problem but there are many paints that will react with resins even if they have cured for a month. I’m not trying to be argumentative, but it is a reality. Fully cured rattle can paints and resins (epoxy & polyester) often react with one another. I can attest to the fact that many epoxy surface coats will stick to lacquers that have cured for several years when just a release wax is used.
Single component paints also don’t work very well with semi-permanents.
On the 2K front, I use PPG Deltron DC3000, allow to cure at room temp for 2 hours, polish, and immediately make the mold with fantastic results…although I use a semi-permanent. Maybe just wax would be a problem.
Again, I’m not trying to argue. I’ve just received too many PM and emails of people over the years who have had sticking problems due to reactivity…which wax is unable to block. In most of these cases they read that PVA was unnecessary on the internet. Some combinations REQUIRE PVA and there is no way around it. If you don’t want to use PVA and you like working with wax then it’s important to test the combination beforehand. Some paint/resin combinations work just fine with only wax and some do not. I just hate seeing peoples hard work end up in heartache. TEST. TEST. TEST. If the plug is vital use PVA as an extra safe guard.
Many laquers and enamels are totally unsuitable. I would not trust any 1K paint for producing moulds, especially with polyester.
The only success I have is with 2K PU paint (not acrylic) which has cured for 7 days minimum. This can be given a good polish, then sealed with semi-perm sealer (Ferrokote FS10), then a wax applied. Seems overkill, but especially at large projects you do not want to run into problems.
Many laquers and enamels are totally unsuitable.
actually i agree with this 100% now brings back memories i have moulded off enamel the paint was 10+ years old and still fryed up on me.
ill modify my post not to confuse anyone.
On the 2K front, I use PPG Deltron DC3000, allow to cure at room temp for 2 hours, polish, and immediately make the mold with fantastic results…although I use a semi-permanent. Maybe just wax would be a problem.
wow thats impressive… must be fantastic paint and release system
It is a fantastic system. PPG Deltron DC3000 High Velocity over the DBC black basecoat, Frekote FMS Sealer, and the Frekote 770-nc release. Add some heat to the process you can speeds things up even faster.
I will say that not all resins will release from the Frekote system though. I also strictly use epoxy surface coats that are brushed on. Sprayed on Gel-coats may experience some beading issues…though I’ve never tried it. Again, it’s very important to test for compatibility first.
BTW, many lacquers and enamels will work just fine if PVA is used on top of the wax.
