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Bottom Job

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MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Apr 06, 2024

Posts: 7088
Posted: Apr 23, 2020 - 12:36 PM

Headhunter why is it critical to wash the amine blush? One would assume you're just sanding off that layer

Jon, wash that blush off!

https://www.youtube.com/watch?v=I3E-ppNtfaU
dcwhite

Rank: Lubber

Registered: Nov 23, 2019

Last visit: Jul 13, 2022

Posts: 34
Posted: Apr 23, 2020 - 01:06 PM

Amine blush is like an oily surface from the epoxy cure (caused by humidity and atmospheric conditions during cure). You need to clean away the oily surface. Cleaning with water or solvent only may leave some amine blush in the nooks and crannys. Light sanding is the best way to remove all of the amine blush. You are not sanding all of the fiberglass and epoxy away, only slightly sanding into the surface for bond preparation so the next layer will stick. If you gel-coat over amine blush or fiberglass over amine blush you will get delamination down the road. Amine blush can also be prevented by putting peel ply over the fiberglass and epoxy before it cures and removing it after cure. This is what many production shops do, but this costs more in consumables.

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David
Inter 20
Southern Maine
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charlescarlis

Rank: Mate

Registered: Jun 30, 2018

Last visit: Mar 20, 2024

Posts: 583
Posted: Apr 23, 2020 - 01:53 PM

DEFINITELY wash out and wipe down the amine BEFORE sanding. Had a real bad experience doing it in the reverse and only embedded the amine, causing fish eyes.

You can get a fine polyester scrim-type cloth from Wally World that works pretty darned good for peel ply, BTW. And, cheap.

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Chuck C.
H21SE 408
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MN3

Rank: Master Chief

Registered: Jun 20, 2006

Last visit: Apr 06, 2024

Posts: 7088
Posted: Apr 24, 2020 - 08:25 AM

QuoteHad a real bad experience doing it in the reverse and only embedded the amine, causing fish eyes.