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Mold release removal

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Old 09-02-2012, 01:05 PM
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BullardRM
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Default Mold release removal

I used alcohol to clean the mold release from a fiberglass cowl. After a fairly short time the paint (PPG) seems to be be popping off way too easily. I wondered if all of the mold release came off when I cleaned it. Should I have used something else like acetone or water? Yes, the surface was primed with PPG primer before painting. Thanks in advance.
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Old 09-02-2012, 01:16 PM
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Default RE: Mold release removal

Most mold releases are soap and water clean up items. That is how we cleaned up the 17-9' boat hulls when we pulled them from the molds, it was PVA.
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Old 09-02-2012, 02:08 PM
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Default RE: Mold release removal

soap and water
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Old 09-02-2012, 03:37 PM
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Default RE: Mold release removal

Soap and water but a dose of 91% alcohol won't hurt either. I would NOT use MEK, Toluene, lacquer thinner, or acetone.
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Old 09-02-2012, 03:50 PM
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Default RE: Mold release removal


Quote:
ORIGINAL: BullardRM

I used alcohol to clean the mold release from a fiberglass cowl. After a fairly short time the paint (PPG) seems to be be popping off way too easily. I wondered if all of the mold release came off when I cleaned it. Should I have used something else like acetone or water? Yes, the surface was primed with PPG primer before painting. Thanks in advance.
I will usually use a Scotch Brite pad and dish soap/water. You didn't say if you sanded the clean surface to break the gloss or not or if it were epoxy glass or polyester.

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Old 09-02-2012, 03:59 PM
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Default RE: Mold release removal

same ? as above,, speed is speedy
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Old 09-02-2012, 04:04 PM
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Default RE: Mold release removal

You usually want to keep the gloss and sanding or scotchbrite will dull it. Just soap and water should be sufficient. Don't over think it.
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Old 09-02-2012, 04:17 PM
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Soap and water work's best for me. While I'm at it I use 400 grit to wet sand. If there's a gloss left it's too smooth for paint to adhere to. All manufacturer's recommend sanding before painting over any type of resin.

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Old 09-02-2012, 04:25 PM
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Quote:
ORIGINAL: Chip_Mull

You usually want to keep the gloss and sanding or scotchbrite will dull it. Just soap and water should be sufficient. Don't over think it.

When painting you need a correctly preped surface. The bond between the paint and fiberglass is a mechanical bond which requires scuffing.

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Old 09-02-2012, 04:43 PM
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I always sand too, ya gotta knock the shine off in my book
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Old 09-02-2012, 05:07 PM
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Default RE: Mold release removal

When you know you are going to paint a molded part stop your sanding it at 180 grit. I gives you somewhat of a paint holding surface for the upper coat. It can not be to rough or your have trouble pulling the part. If you can use a gel coat of the color wanted in the end, then you can go for the perfect shine on the plug. I have spent days in a 19' female runabout mold getting a shine on it.
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Old 09-03-2012, 05:58 AM
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Default RE: Mold release removal

Water.
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Old 09-03-2012, 07:19 AM
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Default RE: Mold release removal

You use water to clean the part.
You must sand a new fiberglass part, 220 grit is best to ruff up the surface.
You must also use theproper primer.
If you can scratch the primer off with your fingernail it is not the right one for fiberglass.
A clean scuffed surface and the correct primer are essential for a successful paint job.
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Old 09-06-2012, 08:11 AM
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Default RE: Mold release removal

Always clean off mold release with soap and water FIRST. Never sand or scuff up the fiberglass until it's been cleaned. Otherwise, you can scrub the PVA down into the glass and cause adhesion problems.
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