Oil over Shallac sealer?

[drmjh]

Hi,
Am just in the process of final assembly of Queen Size 'Craftsman/Mission' style bed and I applied two wash coats of shellac as a sealer.
As an afterthought, I thought I might use an oil mixture: 1/3 oil 1/3varnish 1/3mineral spirits.
My question is, will this finishing technique sit and look well??
Thank you,
dmjh:widea:

 

[4yanks]

I wouldn't recommend it. Shellac contains high concentrations of wax. This would prevent a rubbing varnish from adhering. It is possible to get de-waxed shellac. If you did not use de-waxed shellac initially you can try applying a high quality de-waxed shellac over your original coating and then use a rubbing varnish. I have read that this will work. However, my experience with de-waxed shellac under a rubbing varnish did not work out.

 

[stave]

The three part finish is basically a penetrating oil finish. With the surface sealed with shellac there isn't much to penetrate and of course there is also the wax issue. Personally I like a couple of coats of clear gloss lacquer followed by a satin coat. The gloss builds better and seems to have more strength and the satin just makes for a nicer look.

Stave

 

[CarvedTones]

If it was waxed shellac, that is a concern, but dewaxed shellac if fine; that is what SealCoat is and it works under pretty much anything.

 

[drmjh]

I wouldn't recommend it. Shellac contains high concentrations of wax. This would prevent a rubbing varnish from adhering. It is possible to get de-waxed shellac. If you did not use de-waxed shellac initially you can try applying a high quality de-waxed shellac over your original coating and then use a rubbing varnish. I have read that this will work. However, my experience with de-waxed shellac under a rubbing varnish did not work out.

Thanks everybody! I did use de-waxed flakes to constitute the sealer. I am interested in 4yanks experience with rubbing varnish over this sealer. Was it dull, splotchy, etc.?
Aside from brushing on lacquer (something I'd not look forward to:embaresse, (though I do have 3 cans of spray lacquer, high gloss) what are my other options, besides continuing to build up coats of shellac?)
For my education, would the same thing apply had a "sanding sealer been applied?". When and why should a wood be sealed, I suppose is the fundamental ?
Does one choose the final finish first and plan backwards?
drmjh

 

[4yanks]

Thanks everybody! I did use de-waxed flakes to constitute the sealer. I am interested in 4yanks experience with rubbing varnish over this sealer. Was it dull, splotchy, etc.?
Aside from brushing on lacquer (something I'd not look forward to:embaresse, (though I do have 3 cans of spray lacquer, high gloss) what are my other options, besides continuing to build up coats of shellac?)
For my education, would the same thing apply had a "sanding sealer been applied?". When and why should a wood be sealed, I suppose is the fundamental ?
Does one choose the final finish first and plan backwards?
drmjh

Matt,

My experience was with de-waxed shellac flakes as well. The piece in question was a dresser that I planned to put in my living room to store dvds/cds. It was was going to have a lamp and other things on the top like any side table might. In order to protect it from abrasion I decided to apply a wipe on polyurethane as a final coat for the top. After allowing the finish to cure for a week I applied paste wax to the entire piece. When I did the top surface began crumbling. Eventually it all wiped off. No problem really the piece still looked great just no poly on the top.

As for your question on sealing; almost all finish products seal the wood. In other words prevent absorption by the fibers of oils, dirt, etc.. I think that pre-sealing as a part of the finishing process is appropriate for 2 reasons. First when you wish to retard the absorption of dyes/stains on wood species that blotch easily or have uneven absorption rates between winter and summer wood (i.e. cherry, pine). Second when painting pine to help prevent sap from bleeding through. Their may be others but these are all I can think of right now.

 

[Howard Acheson]

Let me make a couple of points. First, applying shellac as a "sealer" is not necessary at all. The first coat of any film finish acts as a "sealer" in that it seals the pores of the wood preparing it for further coats of finish. Just thin your first coat about 25-30% with mineral spirits and get to work. Shellac adds nothing to the process unless you are dealing with a problem wood link aromatic cedar or if you have stained the wood with a stain that is incompatible or dissolvable in your top coat finish.

An oil varnish mixture that your proposed is intended to be an in-the-wood or penetrating finish. It must be applied to virgin wood. Once you apply a film finish like your shellac, the oil/varnish will not be able to penetrate and be absorbed. When you do the "wipe-off" step you will remove all the oil/varnish finish you applied.

Dewaxed shellac is only required if you plan to overcoat it with an oil based poly varnish or a waterborne finish. If you plan to use an oil based non-poly varnish, a standard shellac is just fine.

 

[drmjh]

Thanks Howard.
I get confused by the terminology. You mentioned that dewaxed S. under an oil based poly varnish would be fine (I don't mean to be argumentative), is that so much different than the 1/3, 1/3, 1/3 mix?
Would you recommend a water based, easily applied product I could use please.
Matt.

 

[Howard Acheson]

Thanks Howard.
I get confused by the terminology. You mentioned that dewaxed S. under an oil based poly varnish would be fine (I don't mean to be argumentative), is that so much different than the 1/3, 1/3, 1/3 mix?
Would you recommend a water based, easily applied product I could use please.
Matt.

A poly varnish is a film finish that produces an ON-the-wood film. Meaning that it stays on top of the wood surface rather than being absorbed into the wood. Therefore it will adhere well to a dewaxed shellac under coat. But, as I have said, there is no requirement for using a first coat of shellac unless you need a barrier coat for some reason.

The oil/varnish mixture you refer to is designed to be an IN-the-wood finish. It must be able to be absorbed or it won't work properly. If the surface has already been coated with a film finish like shellac, the oil/varnish product will not be able to be absorbed. So, yes, your oil/varnish mixture is a quite different product from a film finish like shellac, lacquer, varnish, poly varnish or a waterborne finish.

I'm not sure what you mean by "easily applied" but most big box and internet supplier waterborne clear finishes can be brushed on. Minwax Polycrylic, Varathane waterborne, General Finishes Polyacrylic are a few examples. Buy some and practice on some scrap to see how it handles. How to finish is something you have to learn and practice. Buy either Bob Flexner's Understanding Finishing or Jewett's Taunton Complete Illustrated Guide to Finishing for your best source of finishes and finishing.

 

[drmjh]

Thank you for your patience, explanation and advice.
Matt.:thumbs_up

 

[Jeff]

Matt,

You may want to take a look at Taunton's Finewoodworking, Issue #210, p.38. Peter Gedrys does some interesting things with finishing techniques that may be applicable to your issues.

Zinnser SealCoat dewaxed shellac can be used in a variety of ways for sealing and/or overcoating a lot of finishes. Maybe a follow up on the helpful advice always provided by Howard Acheson. :thumbs_up

 

[drmjh]

Thanks Jeff,
I did take another look at that issue.
Matt.