I am refinishing some ~60 year old doors in my house. I believe they are finished with shellac because denatured alcohol removes it.
I planned to just flatten the old finish, which was poorly applied with a lot of brush marks and dust nibs, then apply an oil based pigment stain (to color any dents, deep scratches, sand-throughs, etc), then spray a fine coat of new shellac over it.
Everything went well through the pigment stain step. I sanded with 100% mineral spirits and wet/dry sandpaper to an even sheen, then wiped the stain on and wiped the stain off. Man did it look good.
Then I sprayed about a 1-2lb cut of fresh amber dewaxed shellac, and the finish crawled badly. My refinishing book (Bob Flexner’s excellent Understanding Wood Finishing) said on the subject of fish-eyes to spray a barrier coat of shellac, because shellac doesn’t crawl! So I tried triple washing the whole surface with a bunch of clean rags and mineral spirits, and tried again, with the same problem. I tried very thin coats of spray which just left me with bad orange peel. I tried a heavy coat which crawled to a comical degree.
Under a printer’s loupe, I can see that there is some alligatoring to the old finish, and that the top (new) coat follows that.
Does old shellac go bad in place on the furniture so that it doesn’t go back into solution evenly? I can remove the shellac relatively easily without damaging the stain; is that my best recourse?
What is up with the crawling?
Replies
Wood,
I haven't used shellac in years. My understanding is that there are not too many advantages to using it. ie. way back when...100's years ago, it was all there was, but now? So many better choices.
Your question seemed to be about alligatoring, but was titled as a fisheye problem. Two different things with different causes. Without knowing more, my advice would be to use a more benign finish like an oil based varnish or urethane.
It shouldn't attack whatever is the original finish is. Just be sure to test for compatability problems with whatever you decide to reduce it with, if you still want to go the spray gun route.
Jon
The old finish was alligatored. The new coat crawled over the old finish, even though it was leveled. Close inspection showed that the alligator cracks had a different affinity for the new finish than the alligator "scales." The difference in affinity is what causes crawling.
What boggled me was that according to all the texts I could find was that it was supposed to be easy to repair old shellac finishes - even "reamalgamating" the finish with just alcohol to rejoin the alligator's scales.
I'm using shellac instead of lacquer because they are antique doors and I want them to stay that way. Also I like the amber color, and shellac is environmentally benign, and generally a joy to spray. It's also easy to rub out. The finish performed well over the past x decades, but the door panels were broken out when the previous owner's children threw each other through them.
I would try rubbing with alcohol rather than mineral spirits, so that the old finish will be disolved...you might need to rub out with 4/O steel wool or plastic equivalent with shellac and clean the surface, but not enough to damage the patina, and then re-try your shellac treatment. Along the same lines, you could try french polishing instead of spraying your initial seal coat, which will cut the surface ever so slightly, and I imagine would give you a very good level even seal coat to build on with your sprayer.
Good luck. Shellac is the best. ---geoff
Shellac over shellac can crawl or alligator, especially when working over an old finish. Oftimes the old finish had some extraneous ingredients, thus the term "spirit varnishes". I have this problem frequently; I do a fair amount of restoration work on shellaced objects; my solution is to spray a very light mist coat if I suspect I will have problems or notice them, which I give some time for it to harden, and then gradually build up the finish. If you haven' removed too much of the original finish, try a light coat of shellac, then wax. Even on new work, if you try and build shellac, or lacquer, they will alligator if you hit it too fast. I personally find shellac easy to work with, and capable of a wide range of effects, and have yet to find a "modern" material with better working charactoristics, except for things that will watermark, like tabletops.
This forum post is now archived. Commenting has been disabled