The Fine Details of Epoxy Use

[psneeld]

Originally Posted by minaret

If your paper doesn't gum at all, you probably have no blush. Scrape a fingernail on it after it cures and see if anything waxy comes up under your nail. It's easy to spot. I can tell just by looking usually, blush spots are glossier. In my experience long cure times and low overnight temps contribute to blush. Also ambient humidity.
Obviously you would want to skip the washing because you are trying to chemical bond another coat and dont want to wait for drying time because you'd lose the window. On a final coat you might as well wash it before sanding, but I always finish with a coat of 407 for sanding anyway and then blush isn't a problem.

If you are building layers before final cure of the last coat... OF COURSE you don't have to worry about the blush (or sanding for that matter)..

[Matt sachs]

Dangnabit.....I have another question.
Each screw (thru plywood) was counter sunk, and the hole wetted with west, once the epoxy became tacky, I filled with thickened west and sanded flat. Then sanded and coated three times with west. These screws are completly invisible. I used low angle lighting and you can't see them.......until I painted it. The morning dew shows every dang one. Once the dew is gone they disappear again. I painted with PPG 450H 2 pot urathane. Will this go away when I apply 2 more coats or do I need to use something different for the final coat?

[barnakiel]

I would work fast and not wait for layers to set. Apply one coat and just when it is tack free follow with another one (and another, if you wish). It is an area work so there will be no issues with overheating, etc.. Chose the hardener that will allow you to work to a reasonable time-scheme.

IMHO the premixed barriers of International are better than pure epoxy if osmosis protection is the target.

PS Add some dye to your epoxy - different each coat - makes the work easier.

b.

[Honey Ryder]

as far as i understand the washing off process is only necessary if you want the blush to disappear, but it is only a cosmetic consideration. if you overcoat then it doesn't matter. as with other epoxies, it is important to apply the second coat of epoxy over the first one while the first coat is still tacky. this ensures a chemical bond between the two coats. if you let too much time elapse before the second coat goes on then it will be a mechanical, not chemical, bond, so you need to key the original coat so the second coat can get a good grip. the chemical bond is much better than a mechanical bond.

[psneeld]

Originally Posted by Honey Ryder

as far as i understand the washing off process is only necessary if you want the blush to disappear, but it is only a cosmetic consideration. if you overcoat then it doesn't matter. as with other epoxies, it is important to apply the second coat of epoxy over the first one while the first coat is still tacky. this ensures a chemical bond between the two coats. if you let too much time elapse before the second coat goes on then it will be a mechanical, not chemical, bond, so you need to key the original coat so the second coat can get a good grip. the chemical bond is much better than a mechanical bond.

Nope...better read up some more...