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Old 12-10-2017, 02:03 AM   #1
Simoncbrr1

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Default Need help making mold. Ideas?

I am attempting to make a mold using epoxy resin. The parts Iíll be made from carbon/vacuum infusion. Usually when Iím making a mold I paint the part with cleat and buff. I use Freekote 770- NC and this seems to work fairly well. The problem is the painting is time consuming. Should I just use PVA? Or can I maybe just apply 770-NC directly to the parts since itís plastic? Looking for a faster way to build my molds. Iím worried that I wonít get the ďperfect partĒ that Iím used to if I use pva. Iíve attacjed photos of the 2 parts I am attempting to make.
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Old 12-12-2017, 10:32 AM   #2
idk

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I would use PVA. The original parts look like they're textured so PVA won't have much effect on the finish anyway. PVA is perfect for this application. It will form a chemical barrier to prevent the resin from reacting with the plastic. It will guarantee a safe release and the original part will still be in perfect condition. If you haven't used PVA or have had trouble spraying PVA, see a post I made regarding that in Tricks of the Trade, page 4. I recently made molds of parts similar to yours and if I knew then what I know now, I would have used PVA and they would have turned out better and the original parts would still look like new.

Last edited by idk; 12-12-2017 at 10:40 AM.
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Old 12-13-2017, 02:32 AM   #3
Simoncbrr1

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Thanks I will try this. Can I use a brush to apply?
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Old 12-13-2017, 03:14 AM   #4
Hanaldo

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Quote:
Originally Posted by Simoncbrr1 View Post
Thanks I will try this. Can I use a brush to apply?
You can, but it is far better to spray. I'd suggest looking for a Preval sprayer if you don't have spray equipment.
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Old 12-14-2017, 04:21 AM   #5
Simoncbrr1

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Ok going to try and order one. Thereís probably a thread somewhere here that explains how to mix it?
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Old 12-14-2017, 04:39 AM   #6
Hanaldo

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No need to mix, can spray it as it is straight out of the bottle.
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Old 12-15-2017, 05:59 AM   #7
Simoncbrr1

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So donít thin the pva at all?
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Old 12-15-2017, 02:07 PM   #8
Hanaldo

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No, there's no need.

If the ambient temperature is very hot, you may find the PVA dries in the air and lands on your part as lumps rather than a film. If that happens then you can add 5% water to the PVA. But otherwise, spray it as is.
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Old 12-26-2017, 10:21 PM   #9
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If, on the other hand the ambient temperature is cool, or the humidity is high, and the PVA still needs thinning, you can add up to 25% Methylated Spirits.
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Old 01-07-2018, 07:39 AM   #10
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Methylated spirit goes under the name of de-natured alcohol in USA. Isopropyl alcohol can also be used to thin the pva.
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