Question About Tooling Gel and Paint,,,,

General Composites Discussions Composites Talk
#1

hey i can’t seem to find the right answer. Aparently the molds i made turned out fine except for the size is off. Tried sanding but i’m about fed up when i sand just a little too much.
Right now I tried my best to form the shape, but it isn’t working. if I use the actual piece which is painted in white and i wax with mold release at least 6 coats, will the tooling gel still be able to take the clear or the paint of the piece? Or will it be safe from the tooling gel?

I want to be able to save the actual piece in paint if everything goes to hell

#2

Welcome moobie, by the looks of your photos on that other site, here’s some tips:

Gel coat should be sprayed, instead of brushed. But if you can only brush it, brush many thin layers and let each one “B” stage first. Also, brush in a cross method, 0 degree first, let it “B” Stage and then brush in a 90 degree direction.

Also, if you don’t get the right % of cataylst to resin, it will hyper exotherm (extreme heat) and then it will bake thru the wax & crosslink to the paint surface.

Use less Cataylst to get less heat, longer work time and less chance of cracks or shrinkage too.

Also, 1x layer of CF will never be enough to prevent gaps or holes.

PS: Most times the cloth will not take a sharp 90 degree where it comes out of the mold so the best way is to trim it to around a 1/2" and letit be straight up out of the mold until it is in the late “B” stage and then green trim it with a metal hooked box knife. It cuts like cheese then…

#3

PVA might help, it would provide a barrier that would protect your paint and help the release.

#4

I dont know how much this helps you but I hate PVA. The work to get the mold smooth and shiney after you use PVA sucks.

I polyester prime everything I do so I dont know about the paint thing. I buff on between 6 and 10 coats of wax to make sure nothing sticks. I have yet to have a problem with gelcoat taking the primer with it.

I brushed on all my gelcoat because I didnt like my gelcoat gun. I am trying to get used to it but it bugs me still. I brush on on really thin coat and then let it tack up to where your finger feels the stickyness but it doesnt leave any on your finger tip and then brush on a heavy coat (dont get crazy) and wait for it to tack up and then one more coat.

When it tacks up like the original description I brush on a layer of resin and then start putting the matt down.

#5

A trick somebody here or elsewhere lead on to after spraying the PVA is to also spray a thin coat (when cleaning the gun out?) of water on to the PVA and it will flow the PVA out better.

My ROP class is getting ready to see the mold building process and I might try it then…

#6

PVA became a ‘magic bullet’ of sorts for our parts. We are making pump casings, very complex geometries with almost no draft in some areas, varying crossections. We were having trouble releasing from the mold until we tried a wax & pva release system together. Two coats wax (three if concerned) then several thin coats of sprayed on pva, spray from all directions to get uniform coverage. When sprayed, the pva layer is very thin and quite smooth, let dry in moving air until dry between coats. Nothing fancy on the spray gun for us either, spent under $20 for it. I would think spraying water on the pva would be pretty tricky, any water exposure I’ve run into after the pva is applied usually winds up in a do over.

#7

Seems you either love it or hate it- I was using carnauba and PVA and just found that while everything was releasing, it seemed like I should be able to get parts to pop like a fried egg on a teflon pan- and while PVA was definitely keep the resin form crosslinking, the slight texture of the pva was almost like a binding agent.

I recently used partall #2 paste-wax all on its own and it works beautiful and parts have a better finish. You simply CAN NOT miss any spots though or it’ll pull the gel/primer up. I’d wax 4-5 times by waxing, letting it set up a bit, wipe the excess off/buff a little, reapply etc, then let the solvents dry out for a few hours, then buff, mechanically if possible.

A decent variable-speed rotary buffer with a 5" wheel (7" if it’s big and flat) saves me a ton of elbowgrease.

#8

With a classroom of Newbies (and some so call experts that turn out to be newbies in wolf’s clothing…), we go ahead and semi pernament coat every mold made. That is after losing a couple of molds the hard way!

But with Semi Pernament mold release, it needs to be heat cycled cured with hot lay up parts with the use of mold release wax and sometimes PVA too.

After that, you don’t need any mold release wax or anything at all!

#9

So by that are you talking about Safelease or similar? Been interested to try that as 5 coats of partall does take a while on big parts. BTW sorry for the threadjack.

To the original poster:
A huge part is what sort of paint is it? If it’s single stage enamel (like from a spraybomb) I would be VERY careful and definitely use PVA.
The one thing pva is good for is as a literal barrier against crosslink. However as you seperate the part, try to get as much water into the “split” as possible to dissolve the pva as you pull the part- the bond between the pva and the part and the mold could still try to lift enamel.

If it’s catalyzed urethane, epoxy, or polyester based then you’re cool.

#10

I always use pva for protection. I’ve had gelcoat mess up too many parts. I can usually lay pva almost paint like. When I do get dry spray with PVA, I use the water mist trick. It works well as long as you don’t spray too much water. When you lay the PVA correctly, there is very little orange peel to take off the mold. I prefer sanding the mold versus replacing a plug due the factory paint finish being stripped off.

#11

Weksberg: When I try an additional heat cure, I get a warped mold or plate. Latest was a ‘flat’ plate that I was going to mount a part onto to build a mold. When I placed the flat plate (1/2" thick, VE resin, 3-4 layers glass matt) into an old electric kitchen oven (170-200 degrees F) for 2 hours, it came out warped! I don’t think the heat is excessive. Can you comment?

#12

Does this mold have any reinforcements like wood, cardboard (poor man’s honeycomb) or anything else for bracing? It should…

But you don’t need to post oven cure a mold if you are using the semi pernament mold releases, but just a few Hot batched made parts with using wax in between each part for maybe 3x parts total.

You should contact your VER supplier to find out the resins temperature range is and if any post oven curing is even needed. If they don’tknow, then you need to find another supplier.