Third coat of expoxy on mahagany still bumpy

[davidpm]

I was hoping it would dry smooth at the third coat but it is not.

Is this normal?

What could I be doing wrong?

[Tom Lathrop]

Not sure what the context is here but if the first coat is bumpy,the second and following coats will be bumpy.  You have to start out with a smooth surface beginning with the wood.  If the first coat raises the grain, you have to make it smooth before proceeding. 

[davidpm]

The first two coats were sanded smooth before the next coat was applied. Is it normal for every coat to have those little bumps?

[PeterP]

David, epoxy is neither paint nor varnish. It is mostly too viscous and lumpy and it does not flow out same way. It is an excellent stuff but you are using it for what it is not meant to be. Do what Tom says and sand between coats. Or, personally, I go over each coat quickly with a cabinet scraper to knock of the big ones. I don't worry about the minor stuff -  then I sand the final epoxy coat slick. Remember it is the final coat of paint /varnish that counts - the intermediate coats underneath do not have to be perfect. PeterP

[Tom Lathrop]

That is what I do also Peter.  I am just finishing up epoxy coating 12 daggerboards and rudders and all the smoothing between coats was done with a scraper.  Sand the final coat with at least 220 grit and preferably 320 or 400 grit with the grain before varnishing.  For a painted surface, the coarser grit will do. 

[davidpm]

OK I got it.

How about 207 hardener vs 205 hardener?

Worth the difference?

[PAR]

West System 207 hardener is intended for clear finishes. Most hardeners will turn the resin slightly yellow, while hardeners formulated for clear coats do this to a lesser degree. Many folks can't see the difference on darker woods.

[wkisting]

David,

Are you, by any chance, working in cooler (sub-70-degrees F) temperatures? The reason I ask is that my Raka epoxy flows noticeably thicker when it isn't very warm out, or when it has been sitting through the night in a comparatively chilly 50- or 60-degree garage. I learned quickly that if I store my epoxy indoors at room temperature, or heat it slightly next to a radiant heater for a few minutes, it will flow thinner and more evenly. Otherwise, it flows in a semi-thick state that causes a wavy surface. Unless, of course, it is 80 degrees out, in which case I set the resin in the sun for a couple of minutes before I use it. (Don't leave it in the sun, as the UV can damage it over the long term.)

If you're getting lots of little hard bumps, it may be that you have dust getting into your coats. I know it sounds strange, but even the minor vibrations from a flourescent light can shake dust out of the light and down onto your surface. That's why folks building furniture-quality boats will sometimes staple drop cloth across the ceiling to cover all lights, etc. Just a thought...

[davidpm]

OK how about after the third coat of epoxy I knock off the bumps with a scraper, sand with 320 so all the shiny is gone and it is smooth.

If their are some small pits left can I go ahead and varnish and expect the varnish to fill and level ok?

[Charlie Jones]

if you put on enough coats of varnish -yep. But it would be simpler to recoat a very thin coat of epoxy and sand it once more if you want a flawless finish.

[davidpm]

if you put on enough coats of varnish -yep. But it would be simpler to recoat a very thin coat of epoxy and sand it once more if you want a flawless finish.

I'll give that a try