Shellac as a barrier coat under polyurethane?

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Old 11-18-08, 01:20 PM
W
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Shellac as a barrier coat under polyurethane?

Hi,

I have a simple but not so simple question. I'm refinihshing a table and had terrible fisheye problems with the poly( minwax satin oil based) I tried adding smoothie, sanding, ammonia and TSP cleaning nohing worked. So I'm at my last step which is trying to seal in the contaminant with Shellac. I used orange shellac from flakes.
I mixed it accordingly and let it sit for a day(24 hours) I m a little confused here because from what I've read it says that in order to dewax shellac you should let it sit for at least 24 hours( for 1# cut) and the wax will settle on the bottom and the liquid should be clear, Is that just for The Bleached shellac or for the orange as well? I only noticed a small amount of wax at the bottom but I poured off the liquid on top and have since put 3 coats on the raw sanded wood. Did I dewax the shellac correctly? and if so can any coating be put on top?

Thanks,

Scott R
 
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Old 11-18-08, 03:08 PM
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There may not be anyone on this site that can answer the question. I understand shellac, a centuries old finish, but I am used to the kind that comes out of a can for the most part. And I try not to mix finishes. I understand how it was done, with flakes and alcohol and cheesecloth, very laborious, but a beautiful finish. I was not aware that wax was a component of shellac, shows how much I know. But it that is true, you will have a hard time with poly. Wax and poly definitely do not mix, and poly will, indeed, fisheye.

Why did you pick this course????

Went to my reference, "Understanding Wood Finishes", by Flexnor. He says, ..."shellac works well as a sealer coat because it sands easily, and if it doesn't contain wax, other finishes will bond well to it."
 
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Old 11-18-08, 07:59 PM
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Bill,

Thanks for the reply, I'm using the shellac as a barrier coat only because I had a terrible problem with fisheying when I went to put a coat of poly on a table I had stripped and stained, and as it turned out the table looks like it had been shellaced by the person who refinished it last because it was the only way I was able to match the deep orange color of the legs of the table.

I have the same reference book But I am just looking for some other input,maybe someone who has used dewaxed shellac under poly.

Thanks
Scott
 
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Old 11-18-08, 11:14 PM
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Most polys are not recommended for use over shellac. Adhesion problems. Poly labels usually state don't apply "over surfaces previously finished with wax, shellac, lacquer, or stains containing wax or stearates."
 
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