OK, I’m at the end of a project with many firsts for me, and I’m having problems with my shellac finish. Everything has turned out pretty nice, including the dye stain (water base, wiped on) and the light coat of oil before the shellac (pure tung), and followed by wiping 7 coats of fresh 2# cut Hock shellac. Now, this project consists of four floor to ceiling bookcases, and I have decided to prefinish everything prior to assembly to avoid all the inside corners. However, the problem I’m having is that I go through the shellac coats (scuff sanding between coats, steel wool rub out) on the shelves, they look great, feel wonderful. I stack them aside to make room for the case back and sides. Go through the same process, same results.
It takes me a couple weeks to get time to assemble them, and now my smooth surfaces are a tad rough, like 180 grit. I scuff them a bit, steel wool a bit, they feel smooth again. Now, a couple days later, they’re feel like they’re roughing up again.
What gives? Should I put more coats of shellac on them, or should I cover them with varnish or lacquer? What am I doing wrong?
Replies
I think your tung oil wasn't fully cured before you applied the shellac, and is bleeding out, forming beads of cured oil. Let the pieces sit in a warm location for a week or so and sand, then let it sit again for a few days to see if it happens again. When you are confident it has stopped you can apply your final coats of shellac.
Rob Millard
Thanks for the help! Man, was I getting worried/frustrated! That makes perfect sense (hindsight being what it is, of course).And I didn't use very much oil at all, just following the padding shellac directions in the Complete Illustrated Guide to Finishing (Jewitt) and immediately followed with the shellac. (Which, BTW is 1.5 days old in the jar, flakes are stored in air-tight container and were maybe a month old) Oops, I guess.I'm glad I asked you guys; I still have three others to finish and assemble!I'll let this one sit for a week and hope it's cured out by then...Thanks to all!
How long did you wait for the oil to cure before you started applying shellac?
How old is your shellac?
You may have trapped uncured tung oil beneath your layers of shellac; if the oil hasn't cured, it'll continue to outgas, softening the shellac. You may have to remove the shellac with denatured alcohol or ammonia if time doesn't solve the problem.
Tung oil is notorious for its long drying time. I use a tung-based finishing oil (Liberon) that polymerizes rapidly, and I still wait at least a week before I apply anything on top of it.
Good luck,
-Jazzdogg-
"Don't ask yourself what the world needs. Ask yourself what makes you come alive, and go do that, because what the world needs is people who have come alive." Gil Bailie
The nice thing about shellac is that it will be easy to fix this problem, once the oil is fully cured. Shellac is one of those finishes easy to strip, or you can just sand it smotth and add a few more thin coats.
The cause suggested, that the tung oil hasn't completely cured is the likely cause.
I would suggest that you are spending way too much time on the shellac, seven coats and you sound like you are still planning more. The wiping technique you are using isn't appropriate if you are trying to build some thickness, just brush on a couple of coats and then maybe a final wipe on coat. Shellac is best used as a thin finish, if you want thickness, varnishes are more appropriate.
John W.
John,Y'know, before I got the "roughies" I thought I was done, and was very pleased with myself for getting birch veneer ply to mimic cherry and match our flooring! Ahhh, the sweet bliss of ignorance...Oh well, if I ain't learning something new, I probably ain't breathing, either!Thanks for the reply; greatly appreciated.Tim
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