Varnish over shellac?


I replaced all my interior doors and trim with shellacked cvg fir. It's beautiful! However, the two bathrooms with showers have humidity problems I didn't expect and the shellac finish is degrading. I would like to varnish the doors on the humid sides to better withstand the humidity.
Can I just sand down the shellac some and varnish over it, or do I have to try to strip the shellac first?
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What kind of shellac? Dewaxed shellac makes an excellent undercoat. The 'naturally waxy' kind, not so much so.
In either case, since this has been in use, SOME sanding is in order. And/or a wiping down with denatured alcohol. A coat or two of dewaxed (think Zinsser Sanding sealer) over what you have should be ok, after the cleaning, even if there is wax in your earlier coats.
I'd at least consider using a urethane gel wiping varnish for the top coats, because of ease of application...
Patriarch
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If it were me I would sand down the existing shellac some, clean it well, apply a dewaxed shellac (Zinnser sealcoat?) and then apply your preferred topcoat(s).
Dave Hall
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Thanks for the advice. I used dewaxed shellac originally, but I'll apply a wash coat before varnishing just to make sure.
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