The Fine Details of Epoxy Use

[Matt sachs]

whew......I'm 14 gallons (and a year and a half) into this boat. Sanding, not washing....But when I sand it, it's not just a quik hit with a sander. I remove about half the prior coat with 40 grit and a DA sander. Then I clean it up, wipe with a damp cloth, leave it in the sun for a few minutes and recoat. Somebody tell me I havent wasted a butt load of time and money.

[captain58sailin]

There used to be a product in the grocery store called sudsy ammonia and the recommendation was cut it down and use it with water, like a half a cup to 5 gallons of water. The other proviso was if you put another coat down before the first coat cured you were okay. I tried to put the coats down before the previous one cured, and when I didn't get to it in time, I would wash it before sanding. Mind you this is in Alaska in the out of doors so the cure time was much greater than down south.

[psneeld]

Originally Posted by Matt sachs

whew......I'm 14 gallons (and a year and a half) into this boat. Sanding, not washing....But when I sand it, it's not just a quik hit with a sander. I remove about half the prior coat with 40 grit and a DA sander. Then I clean it up, wipe with a damp cloth, leave it in the sun for a few minutes and recoat. Somebody tell me I havent wasted a butt load of time and money.

You may have....even the most basic research on Epoxy work talks about amine blush and ALWAYS washing prior to sanding as sanding just contaminates all the great scratches you just put in the base layer.

[Matt sachs]

I'm finding out that even if the ambient temp is in the seventies,( as it has been here for a few weeks) if the substrate is in the sun and warm the slow cure works fine. However, if you mix the fast cure when the ambient temp is 90+ you have an interesting problem.......

[Matt sachs]

I'm not arguing, just confused, why wash it then grind the washed surface away?

[minaret]

Originally Posted by Matt sachs

I'm asking to see if I have screwed up to badly....

The chemical film is called blush, and it doesn't always happen, particularly with WEST. Unless you were having a problem with blush, it's not a concern. When you sanded, was there a waxy film on the surface? Did your sand paper gum up? If not, you probably had no blush. WEST is the least prone to blushing of all the epoxies I have used.

[psneeld]

Originally Posted by Matt sachs

I'm not arguing, just confused, why wash it then grind the washed surface away?

When you sand ANY film it takes awhile to get rid of it all..the EASY answer is just wash it away first.

The trouble with GUESSING whether you have a blush is that you are guessing...haw hard can washing the surface be to make sure???

Plus there are epoxies out there that discuss NO amine blus with their product...I would never blindly assume WEST was that way unless I had tons of exerience with it...which I do....

[Matt sachs]

No, the sand paper dosen't gum up. One disc lasts about a half hour.

[HopCar]

The film you folks are speaking of is called "Amine Blush". Older epoxy formulas like WEST have to have it washed off once it has developed. New epoxies like MAS don't develop the amine blush. I have no idea what amine is but I'm sure one of our CF chemists will be along soon to explain it.
The mica chips in the Interlux products force the water to travel around them which makes it as effective at stopping the water as a much thicker coating of epoxy without the mica.

[Matt sachs]

Thanks for the input guys. I will certainly wash it from now on.

[minaret]

Originally Posted by HopCar

The film you folks are speaking of is called "Amine Blush". Older epoxy formulas like WEST have to have it washed off once it has developed. New epoxies like MAS don't develop the amine blush. I have no idea what amine is but I'm sure one of our CF chemists will be along soon to explain it.
The mica chips in the Interlux products force the water to travel around them which makes it as effective at stopping the water as a much thicker coating of epoxy without the mica.

I've used literally thousands of gallons of epoxy in my career and MAS had the most severe blush problems I've ever seen. I wouldn't use it if they gave it to me for free (which they have in the past). WEST is the only way to go for me.

[minaret]

Originally Posted by Matt sachs

No, the sand paper dosen't gum up. One disc lasts about a half hour.

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.

[Matt sachs]

This is the only close up picture I have of the epoxy just prior to sanding....and a stupid little bee. Does it show anything that I need to be aware of? This is 12 hours after I applied it.

[captain58sailin]

Stop letting the bugs crawl around on your fresh epoxy! Man I hate that!

[Boracay]

I've been using epoxy to seal the wood on Boracay. Mostly I thin about 10% and let it penetrate. Then I topcoat with varnish or enamel.

I found, even thouh the epoxy I was using was said to be non blush that I was getting an "orange peel" effect. I now know that this was most likely due to the waxy "blush" repelling the topcat.

Now I scrub down with a kitchen scourer and a little cloudy ammonia and let dry before topcoating. No more orange peel. Easy peasy.

Just sanding seems to smear the waxy stuff all over the place and does not seem to help.

Now, even if using the best non blushing epoxy in the world I'd be tempted to wash with warm water at the very least after the epoxy had fully set.

That finish in the "bee" photo looks a bit waxy to me...