Furniture, Wood and Cabinetry Finishing - sanding sealer & polyurethane
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01-27-01, 09:01 AM
I have read on this site that you cannot use polyurethane over sanding sealer. I have a can of Minwax sanding sealer that recommends using polyurethane over the sealer. Can you tell me which one is correct? Can tung oil be used over the sealer? Also can polyurethane be put on over tung oil? Thank you for any help.
George
01-27-01, 06:40 PM
I could swear I answered this question in another forum, but here goes.
When first introduced, polyurethane did NOT have a comparable sealer on the market. It now does.
To digress slightly, sanding sealers, whether for varnish, polyurethane or lacquer have a two-fold purpose. The obvious is to seal the wood so that following coats of finish sit ON the wood and don't soak in; the sanding part comes in as sanding sealers are made to be sanded. This prepares (smooths) the surafce for application of finish coats that go on more smoothly. Sanding sealers are softer than the finish that covers them and, generally speaking, are not necessary. With either varnish or polyurethane I use a thinned coat of the finish as a sealer and don't worry about this being harder to sand. I'll normally do a lot more sanding on the second and third coats anyway, so the time and effort saved by using a sanding sealer are inconsequential.
If the polyurethane sanding sealer is oil based, you can probably get away with using tung oil over it. I can't say for sure, as I have never tried it.
Again, if the polyurethane is oil based, you can probably get good results using it over tung oil.
In either case, the previous finish must be totally cured and well sanded for proper adhesion of the new finish.
When first introduced, polyurethane did NOT have a comparable sealer on the market. It now does.
To digress slightly, sanding sealers, whether for varnish, polyurethane or lacquer have a two-fold purpose. The obvious is to seal the wood so that following coats of finish sit ON the wood and don't soak in; the sanding part comes in as sanding sealers are made to be sanded. This prepares (smooths) the surafce for application of finish coats that go on more smoothly. Sanding sealers are softer than the finish that covers them and, generally speaking, are not necessary. With either varnish or polyurethane I use a thinned coat of the finish as a sealer and don't worry about this being harder to sand. I'll normally do a lot more sanding on the second and third coats anyway, so the time and effort saved by using a sanding sealer are inconsequential.
If the polyurethane sanding sealer is oil based, you can probably get away with using tung oil over it. I can't say for sure, as I have never tried it.
Again, if the polyurethane is oil based, you can probably get good results using it over tung oil.
In either case, the previous finish must be totally cured and well sanded for proper adhesion of the new finish.