Replies

1. 
   HowardAcheson | May 29, 2003 07:22pm | #1

   Using a dewaxed shellac as an undercoater is a good thing to do. Dewaxed shellac is one of the best barriers to water vapor. It is also an excellent base coat for any subsequent final finish. Two or three coats of varnish or poly varnish over dewaxed shellac makes and excellent, durable and water resistant finish for a tabletop.

   Look at it this way, if you didn't use shellac and the integrety of the varnish was breached, you would still have staining or ring problems with the tabletop.

1. 
   johnnyd | May 29, 2003 08:37pm | #2

   Thanks for the input...now a related question:

   I have a friend who needs to refinish some trim that was originally varnished about 10 years ago.  Looks mostly like scratching from dogs claws with some minor chipping.  If the the original surface is sanded in prearation for refinishing, would this also be an application for wax-free shellac primer-sealer with finish varnish coat?

1. 
   HowardAcheson | May 30, 2003 02:14am | #6

   One of the best uses of shellac is as a barrier between finishes. Shellac will stick to most anything and most anything will stick to dewaxed shellac.

   But, in the case you present, a sanding of the original finish and a new coat of varnish is all you need. There is no need for the shellac. New varnish or poly varnish adheres to abraded old varnish just fine. Just be sure it is sanded well and wiped down with mineral spirits to remove any old gunk. Keep changing the face of your wiping rag to prevent smearing stuff around.

2. 
   DonC | Jun 02, 2003 01:26pm | #8

   Most here have recommended dewaxed shellac. Is shellac sold in a waxed version? If so, when/why do you use it?

   Thanks,

   Don

1. 
   BenM | Jun 02, 2003 02:51pm | #9

   "Waxed" shellac is only shellac that has not had the wax removed.  Waxed shallac has no benefits over dewaxed except that it is usually cheaper.

2. 
   ownersrep | Jun 02, 2003 04:31pm | #10

   Shellac naturally contains wax.  The wax can cause problems (blotching, etc.) particularly when used under other finishes.  The prefered shellac has the was removed (dewaxed).  Unfortunately the only premixed shellac available contain wax.  Apparently dewaxed shellac is less stable and so is not sold as premixed.

   FYI

   Edited 6/2/2003 9:49:58 AM ET by Jim in CO

1. 
   SgianDubh | Jun 02, 2003 05:22pm | #11

   Not quite true, Jim. Zinnser have been selling SealCoat for a couple of years now. It costs me about $9 for a US quart from my polish supplier, or about $25 a gallon. It's a dewaxed shellac formulation that can be used as a finish in its own right, but is marketed as ideal as a primer underneath any other film forming polish.

   For, example it is good at creating  a barrier coat on 'difficult' surfaces-- I've used it successfully over old furniture where I was suspicious that wax and other impurities might still be present. I've used it over oily woods prior to polishing with another type of finish, and between staining/dying and grain filling operations prior to spraying with a catalysed lacquer. Lastly, I've used it under oil based varnish to reduce the initial colour change the varnish might cause if it's the first coat.

   I've not used it under any water based varnish products as I don't  polish with these, so I can't say how it performs here. Without checking their website for confirmation, and completely off the top of my head, I think the stuff is formulated in a two pound cut. Slainte.

   Website                                            The poster formerly known as Sgian Dubh

   Edited 6/2/2003 10:28:00 AM ET by RichardJ

1. 
   ownersrep | Jun 02, 2003 07:25pm | #12

   Richard,

   Thank you, I stand corrected.  I'd just read the bit about dewaxed not being available in some woodworking book (Jeff Jewitt?) yesterday.  Evidently an old book.  I have some Zinner - guess I should have looked at the can.

   Jim

2. 
   SgianDubh | Jun 02, 2003 07:53pm | #13

   Jim, as far as I know, only Zinnsers SealCoat is formulated specifically to be wax free. Their other products-- with a percentage of wax-- can be used successfully under only some film finishes, but the SealCoat (I have heard) is safe for use under all film finishes-- but as before, I have no experience of using it under water based products to know how it performs there.

   Whether or not SealCoat, or any other form of shellac should be used as a primer, sealer coat, or barrier coat is probably dependent upon the proposed final end use of the piece of furniture (or item of woodwork.)  Slainte.

   Website                                            The poster formerly known as Sgian Dubh

   Edited 6/2/2003 12:59:16 PM ET by RichardJ

2. 
   Kevin | May 29, 2003 10:56pm | #3

   Question...if you used a shellac/poly combo like this on a table top, or other horizontal surface, probably with TWO coats of poly....after a few years of wear and tear, would a glass of wine or scotch on the rocks spilled a little develop the famous white ring if it got in under the poly through a scratch or mar?  Or is it laquer that can get the white rings?

   It's uncatalyzed nitrocellulose lacquer that's famous for the white ring problem. If it's not too deep it's not very hard to fix, though. But... straight nitro lacquer isn't nearly as durable as your Varathane poly anyway.

   Regards,

   Kevin

3. 
   chairmake1 | May 29, 2003 11:04pm | #4

   shellac is a great barrier coat - I buy the dewaxed shellac in the form of flakes and mix as I need. I always have some mixed up in the paint booth. Mostly use a 1 or 1 1/2 pound cut and it is also used as a fill coat on bare wood that bloches - like birch, cherry & pine -

   if you put a coat of shellac on the bare wood of these species and then apply your stain you will have a very nice even coat with no unsightly blemishes. Some companies make a pre-stain to apply before the stain - don't but them anymore just use the shellac. It's a versitle finish product.

   Robert

1. 
   johnnyd | May 29, 2003 11:52pm | #5

   But do you ever use it as a primer-sealer on a sanded, previously varnished surface, with re-varnish topcoat, or is that an application better suited to oil-based primer-sealer?

   TIA

1. 
   chairmake1 | May 30, 2003 07:42pm | #7

   in a word - yes

   this will give you a sealer layer - keeping what ever is below from bleedintg through and ruining your top coat.

   Robert