finishing over Epoxy questions

Re: finishing over Epoxy questions

Dick Coers

It's my guess the epoxy will craze with a lacquer finish. You might get by with it if you really dust on the first few coats, but I've never applied lacquer over epoxy. Testing will be mandatory!

Re: finishing over Epoxy questions

Jesper, Denmark

There should be no specific reason why laquer wold not stick to epoxy. There can be a so-called amine blush on top of the cured epoxy. This is water soluble, so a wipe with a wet rag dissolves the amine blush, and you should be good.

I have not specifically used lacquer, but just about any other finish over epoxy: Polyester resin, varnish, solvent borne paint etc.. I do not like waterborne finishes, so have not used those.

Re: finishing over Epoxy questions

Doug Wolf

Barry, Here is a picture of the side of a 11" walnut bowl I filled with 30 minute epoxy mixed with gold Pearl-Ex powder. I put Dark Walnut Watco Danish Oil on it and after it dried for 3 days I used Deft brushing Lacquer for the finish. I brushed 3 coats on and smoothed with a green Scotchbrite pad between coats. It's a year old and holding up well.

Re: finishing over epoxy

Mark Mandell - Gone Round In New Jersey

Test is the rule but a tie coat of shellac will solve any issue.

Attached is epoxy finished with Waterlox red can, then 2 coats of 1lb dewaxed shellac topped with 3 wet coats of GF Enduro gloss WB Poly

The U-Tuber is likely thinking that lacquer thinner will clean/thin uncurred epoxy and acetone, a component of lacquer thinner, will dissolve cured epoxy. Thing is the lacquer solvents flash off so fast it's unlikely they'll have much, if any, effect. Shellac will prevent the interaction and also give your finish more visual depth so what's not to like?

Re: finishing over epoxy

Barry Irby

Thanks,

I was thinking about shellac. I think I will try that.

I tried straight lacquer on the back. I had taped it off to prevent leaks and it turns out the spots are much bigger on the back so it was a good test. Even with the shop cool it worked well. No apparent damage.

Re: finishing over epoxy

William Duffield

The only potential problem with a shellac barrier between the epoxy and the lacquer is that the lacquer solvent also dissolves shellac. To keep it from running, make sure your first coats of lacquer (preferably sprayed, not brushed) are very thin so they don't move the shellac around.

Re: finishing over Epoxy questions

TM Stock

Lacquer over epoxy is a very common finishing system for guitar builders - pretty much one of the standard pore-filler/finish combinations in luthiery, where finish is always a make/break on a sale. I also see a fair number of builders using epoxy/waterborne finishes, and I've been trialing EnduroVar over both West 105/209 and System 3 SilverTip epoxies.

Things to watch out for/be aware of:

- Biggest issue is removal of amine blush if the epoxy is not a blush-free formulation...detergent and water, followed by final sanding and toothing should be a reliable means to remove any blush. Check with the manufacturer of the epoxy to confirm that the epoxy will/will not blush. My current favorite is System 3 SilverTip, which lacks the slightly amber color of West 105/205 or Z-Poxy finishing resin. I have stopped using Z-Poxy due to some concerns with continued shrinkage in some batches and excessive blush, but it is still a commonly used filler under lacquer.

- Shellac may be used as a tie coat with epoxy, along with the specific vinyl sealer called for by the lacquer manufacturer. For waterborne urethanes such as EnduroVar, no tie coat is used.

- If using the epoxy to pop the grain on woods that do not require pore filling, leave a very thin coat of epoxy on the wood - sand throughs to raw wood will be very visible on some woods (as a color and reflectivity/chatoyance change).

- Because epoxy penetration varies by product, species, and wood density, luthiers that use epoxy either do a full sand-back to wood or a final, very thin coat to ensure a uniform surface.

- Keep the applied epoxy coat thin - an Etore window-washing squeegee is the best thing I've found for applying and removing the excess epoxy. MyYouTube videos on epoxy pore filling cover prep and the mechanical aspect of application and removal...search on 'Epoxy Pore Filling Part 1"...focused on guitar bodies, but generally applicable.

- Both lacquer and epoxy can be vile stuff; wear gloves, respirator, and eye protection, if you are not yet sensitized to the nastier stuff in epoxy, the stuff seems fairly benign, but the solvents used for epoxy clean-up (denatured alcohol and acetone/lacquer thinner) are dangerous in and of themselves. Avoid the issue - use good medical-grade nitrile gloves and change them frequently if exposed to raw solvents (most of the nitrile disposables will take a good hit of acetone, but thicker gloves are needed to withstand repeated exposure).

Wow! Thanks, very detailed

Re: finishing over Epoxy questions

John K Jordan

>>>Lacquer over epoxy is a very common finishing system for...

Thanks for writing this. This one goes in my files. I want to buy your book when you write it.

JKJ

Re: finishing over Epoxy questions

Don Stephan

One of the best "how I do it" videos I have seen. Didn't notice any missing details, clear explanations, and no wasted time.

Re: Pore Filling Videos

TM Stock

...also a very reliable, non-habit-forming sleep aid

Re: finishing over Epoxy questions

AZ in Colorado Springs

I've patched small voids with epoxy and finished with iul based polyurethane. Bulletproof.