Finishing over Shellac
10/22/25
Website: http://icarusfurniture.com
It came from our public library, and I would like to see it go back on display there. I've already recoated it with several coats of shellac, and am now thinking of putting something harder over it.
I know better than to use polyurethane because of adhesion issues. Can anyone recommend another varnish that I could put on top?
I prefer to spray but could brush as well.
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10/22/25 #2: Finishing over Shellac ...
could spray dewaxed shellac over the waxed and then polyurethane or spray lacquer.
10/23/25 #4: Finishing over Shellac ...
Just leave it with the shellac on it. If you put poly over it, the poly will eventually crack and fail depending on how much shellac is on the piece. You are really not gaining much by spraying lacquer over it now.
10/28/25 #5: Finishing over Shellac ...
Website: https://www.njfurnituremart.com/
You could try dewaxed shellac followed by a hard oil-based varnish like Waterlox or Pratt & Lambert 38 for better durability and compatibility. These offer a warm finish, good adhesion, and can be sprayed or brushed easily.
10/30/25 #6: Finishing over Shellac ...
Website: http://www.bhdavis.net
I've always said "shellac sticks to almost anything and almost anything sticks to shellac". I would do some testing on scrap wood first but I'd think you could go with most modern finishes shy of a 2-part catalyzed system which usually requires it's own seal coat product.
There are a lot of good water based finishes out there now. Talk to your local supplier to see what they carry.
BH Davis
11/2/25 #7: Finishing over Shellac ...
BH is correct to a point. If you have too much shellac on the piece and then top coat it, you have a soft vs hard issue. The hard finish will eventually crack and it may not happen right away on a sample. As a thin seal coat or barrier coat it should be fine but any more than that, I would not recomend. I have had issues many years ago where I had to much shellac under a harder top coat and had to redo it.
11/3/25 #8: Finishing over Shellac ...
Thanks for the feedback.
The General Finishes tech support guy said that it was particularly a problem with Polyurethane's lack of adhesion to shellac— they are a particularly difficult match. I take your point about hard vs. soft finishes, though. What do you think abokut something very flexible as a topcoat, like spar varnish. For instance, McClosky's, which I believe is tung and phenolic resins?
11/4/25 #9: Finishing over Shellac ...
The issue that I had with a top over shellac was actually with poly. This was many, many years ago before I knew better....The top coat cracked so in my mind, if there was an adhesion issue, it would flake off, not crack.(?) I would not topcoat the shellac. No finish will last forever and if it is just shellac it will be easy to repair in the future. I dont have any experience with a phenolic resin over shellac so I cant comment on that.
They used to use shellac on floors....There is an additive you can add to it to make it more durable but I would have to look into some old french polishing books I have to get more info on that.