Replies

1. 
   JiminFla | Sep 30, 2008 11:15pm | #1

   Shawn,

   You are pretty safe with a shellac basecoat.  You can continue to build up a shellac finish if the table top isn't going to get a lot of wear, or you can use varnish or lacquer over it.  The shellac basecoat seals the wood to some degree, so you won't get the same amount of penetration with oil as you would if you applied it to bare wood.

   Jim

1. 
   essdog | Oct 01, 2008 05:17am | #3

   Thanks Jim,

   I think I'll go for it.  Do you know if there is any risk of adhesion failure down the road or anything like that?  Would a poly/oil combo work in addition to a varnish or lacquer?  (I happen to have a Sam Maloof brand 1/3 tung oil, 1/3 linseed oil, 1/3 poly mixture)  Don't sweat it if you don't know the answers to that.

   thanks again!

   shawn

2. 
   HowardAcheson | Sep 30, 2008 11:47pm | #2

   If your shellac was dewaxed, then you can top coat it with any finish.

   However, if it was not dewaxed you should not overcoat it with oil based poly varnish or any waterborne finish.

   Howie.........
1. 
   essdog | Oct 01, 2008 05:21am | #4

   What happens if you do coat shellac that hasn't been dewaxed with a poly/oil combo finish?  Would it peel off over time or just not adhere when applied?

   Trying to learn from those in the know.....

   thanks,

    

   shawn

1. 
   user-83153 | Oct 01, 2008 03:58pm | #5

   Shawn,

   I posted a detailed answer to your question about this in Peter Gedry's ask the experts forum.

   You should look into buying the book "Understanding Wood Finishing" by Bob Flexner. It is very informative about all aspects of finishing.

          Rob

1. 
   stillfigurinitout | Oct 03, 2008 05:51am | #10

   I agree.  Bob Flexner's book "Understanding Wood Finishing" IS the bible of finishing in my opinion.  So much so that I replicated and laminated many of his tables to use in the shop.  Having read more finishing books that I care to mention, I became more confused because even the book writers sometimes get it wrong.  They can contradict each other.  So who do I believe?  Bob is the real deal.  No fluff, no contradictions.  It's all revelation.  You will come away feeling, dare I say, expertish, yourself.  Jewitt's tome is also good, but I'd read Flexner first.  One of the best things Bob does is to list most all the major retail finishing products by name - all the Watcos, General Finishes, Pro-Fin, all the Minwaxes, Waterlox, stains, dyes, etc. - and tells you exactally what they are and what they do, and don't do which is important.  By the way, I found Bob at the library.  I think most carry his book.

2. 
   JiminFla | Oct 01, 2008 04:41pm | #6

   Shawn,

   You should use dewaxed shellac to make sure that you eliminate this as a potential cause of adhesion failure.  You can make it up from shellac flakes and denatured alcohol yourself or buy it ready made.  Zinnser makes ready-made shellac both ways.   I suggest that you follow Rob A's advise and check his response in the "Ask the Experts" forum.  Also, there are several excellent books about finishing that are available and you should pick one up.  Rob mentions Bob Flexner's book, but Jeff Jewett and Michael Dresdner also have written good ones.

   Jim

3. 
   HowardAcheson | Oct 01, 2008 06:22pm | #8

   You will end up with less adhesion. This can mean that the finish may chip and not be as durable as it could be. It may also be able to be scratched off more easily.Many, if not most, poly and waterborne finishes warn not to apply over shellac.Howie.........

1. 
   Gretchen | Oct 02, 2008 04:54pm | #9

   But a NON polyurethane finish can be used over any shellac. Simple solution.Gretchen

3. 
   SteveSchoene | Oct 01, 2008 05:39pm | #7

   Any time wood has been sealed with a film finish, oil/varnish mixes should be ruled out.  Oil/varnish depends on penetration for its effect.  It must be applied, let to soak for a short time, and then have all finish on the surface wiped off.  If done right on a sealed surface virtually all the oil/varnish finish would be wiped off.  And, if any were allowed to stay on the surface that would be soft and almost gummy. 

   That said, a single light coat of 1# cut shellac won't really seal the surface very well, so you might get away with the oil/varnish. 

   Unless the shellac were dewaxed I would still shear away from polyurethane and waterborne finishes. 

   By the way, oak isn't likely to show much blotching.  Pigmented stain can emphasize the patterns of the pores, but that's really not the same thing, and won't be cured by a light wash coat.