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The Shellac hoax

8472 Views 103 Replies 38 Participants Last post by  ETwoodworks
Conventional wisdom has it that new wood should be "sealed" with shellac to start the finishing process. That's pure baloney promoted by Zinsser to sell their products. Any kind of resin finish will "seal" itself. For an expose of the shellac hoax, check out Bob Flexner's article in the September issue of Woodshop News.
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It's not a hoax when using waterborne finishes.

I've done plenty of finishing with zinsser sealcoat and without it before applying my choice finish, crystalac super premium. Much less, if any grain raising with the sealcoat. I realize I could use any number of oil based finishes first, but they take too long to dry for my preference, plus I can tint the sealcoat if necessary with transtint, which I've done before as well. Sealcoat dries in less than 30 minutes.

Even Marc (the wood whisperer) did a recent project (stepping stool) where he sealed the stool first with a coat of sealcoat and then went on to use minwax poly wiped on. He did this because he'd have to put more coats of the poly if he didin't seal the wood first.

I like flexner's book for the most part but I really don't agree with some of his beliefs.

If sealcoat is baloney, why does it work so good?
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Nor is it a hoax if you are going to stain. Then again any sealer would do, not just shellac.
The only hoax I know of that involves shellac is that its not durable,etc.
The huge beauty of shellac is that it's a barrier. This is lost on folks who use typical home center products, as they dry too slowly to be used with the barrier.

As NiteWalker mentioned, it can prevent waterborne finishes from raising grain. It can also prevent oil based brush or wipe-on varnishes from moving oil-based stain pigment around.

Also, shellac can act as an "undo" between professional dyes and pigment stains. Dye the wood, coat with shellac, apply dry brushed pigment stain. Don't like the pigment? You can wipe it off with mineral spirits without disturbing the dye! ;^)

Shellac is also a wonderful finish in itself. It dries super fast, wiping to a wicked fast, shiny build, and it wet sands nicely using mineral spirits as a lubricant.
So you're saying that a company is promoting the use of its product to accomplish a necessary task? Horrors!
Here is the article:

Basically he makes the wrong argument… that shellac is difficult to use. I don't find it difficult to use. In fact I find it easier than poly or varnish and more durable than wiping varnish unless you build up a lot of coats. A sealer coat of shellac sanded smooth is much faster and easier than a sealer coat of varnish and much easier to sand. Plus I like the amber tint.
wormill, nice article the guy gave his opinion, good read. I think we all have our own stiles and preferences.
Quite frankly I love zinsser products.
I have used Zinsser shellac and it turns out really beautiful on most any wood because it gives it a warm glow, which is desirable in some cases. I also use the wax free variety as a sealer for lacquer.

I use a larger variety of finishes and try to use a finish that enhances the look of the project instead of having a favorite finish …. or perhaps I am reading too much into the responses posted here?
Recently I found a can of Zinsser shellac that's probably several years old. 'It's no good,' I thought. Used it on a footstool project anyway and it's as good as the day I bought… so far, hoping it doesn't wrinkle.
Woodshop Newsw is worth reading, but the target readership
is shops with higher-volume spray setups and low-dust
spray booth setups. I reckon Flexner is advocating for skipping
the changing of finishes (and solvents) in spray equipment.
That's fair, because shellac will gum up in the nozzle if you
aren't spraying it in shorter intervals. If you are spraying
another finish on top you have to have another gun and
keep the flow-through on the shellac gun going too.

Sounds like multi-guy shop activity to me.

I use shellac a lot. I never spray it. It dries fast. It is compressible
and polishes out well. It seals pitchy woods like pine for painting
very well.
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@wormil: According to zinsser; their shellac products have a 3 year shelf life.
Very interesting topic and useful to know the properties of Shellac
For me, shellac and/or sealcoat, are the easiest to use and get great results from, out of all other finishes. Sprays great right out of the can, brush, roller or rag it on, it's hard to screw up.
Keep in mind that there are as many different ways to finish as there are finishers. Writing a book about finishing is problemary because once you get past the science, it's all personal opinion and experience.
Excellent sealer. As a painter I've used BIN and Bulls Eye primer for years on smoke and water damaged ceilings or knotty wood. It's basically white pigmented shellac. Don't bother with Zinsser's latex based stain-blocking ceiling paint - it doesn't and it isn't. Need to go to their shellac or oil-based products to cover. Most wood pieces I refinish are done in clear shellac followed by rubbing with 0000 steel wool and clear paste wax. Wood should invite you to touch it - not look like a piece of plastic.
The best part of this discussion is that I don't have to quit using shellac.
It is kinda like my old C'man King Seely drill press. It still works very well even though its old school.
Nonetheless, shellac is good stuff. The frame for my shop sign was shellac'd and it's outside and still looks brand new. I didn't even use anything beyond shellac.
"It's not all hype!"

Bob, doesn't tell you there is a time and place for both dewaxed & shellac with wax. Waxed shellac is great for new furniture where shellac going to be final finish. Dewaxed shellac great for pre-staining, end grain, blotchy woods, and woods with high tannin content. Of course up to you to used eith waxed or dewaxed shellac as final finish.

Experienced refinisher and finishers know when to use either waxed or dewaxed shellac to obtain color needed for a piece working on.

It is true many stain/finish manufacturers recommend a pre-stain conditioner product when using their product on softwoods or porous woods. Is that hype check MSDS for the pre-stain conditioner product! Dewaxed shellac might be better option. Some stain manufacturers do recommend you not use shellac with their stains because it distorts color of stain.

Bob did not mention 1lb cut or less spit-wash coat. Difference between spit-wash coat and sealer coat is the cut or shellac to alcohol ratio. Both cuts do same thing!

Before 2 & 3 lb cut cans of shellac arrived at stores refinishers and finishers have been using a spit -wash coat 1lb cut of shellac as a sealer or barrier coat between other finishes or stains for very long time
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Not sure about the hoax? Zinnser can promote its product however it wants and in my opinion it's valid.

For me, dewaxed Sealcoat is the MVP of products. There are simply things I cannot do with out it, particularly if I seek to deliver color to the wood. It's my main vehicle for adding dye colors as a toner and it always gets used to seal the wood before a stain, which I absolutely abhor otherwise.

But yeah, shellac isn't needed always. But the great thing about it is that there's really no place you can't use it. It's so universally compatible with just about any other product you use. When in doubt, bridge your coats with shellac, particularly if you are wiping/brushing on a film finish (like poly) that uses the same solvent as what you are putting it over. I can't tell you how many times I've rubbed off a gel stain because I neglected to bridge my poly coats with some shellac sealer.
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To clarify a point, shellac was heavily marketed as a sealcoat. It's not really a "hoax". Back when home woodworking became popular, shellac was pretty much all you had to work with as a hard, durable finish coat. Then came along a whole host wiping varnishes like Formby's tung oil finish (contains absolutely no tung oil), Waterlox, etc. which were much easier to work with. To stay relevant in the market, Zinnser pushed the seal coat properties and aspects of shellac. Rather than try to compete with the huge storm of new products people were snatching up, they pushed their product as complementary to varnishes; not an alternative or replacement of - which shellac essentially is.

I was always taught (and just read a book that reinforced this) that the shellac seal coat is not as necessary as people make it out to be. There are a few uses where it excels (I am talking about shellac as a seal coat, not a finish coat):

1 - before waterborne finishes (as mentioned)
2 - To seal off overly oily woods or sappy knots (like in pine)
3 - Odor barrier used when refinishing (pet stains, smoke, etc)

Other than that, your first coat of finish is your seal coat. Shellac is just another finish. It works well as a barrier for the list above, but any other finish will do just as good of a job sealing the wood. I've never seen this happen personally ,only in pictures, but because shellac dries SO HARD it is possible to crack it under your actual finish with some concentrated force.

In addition, dewaxed shellac offers much better moisture resistance than the waxed variety. Since shellac has a short self life, if you use it a lot it is cheaper to cut your own.
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