Well I have been woodworking to one degree or another for almost 30 years. It’s not a profession. I have a question concerning finishes. In the Feb. 2004 issue of Fine Woodworking there is an article by David Sorg intitled Varnishing Secrets. After sanding and dusting he puts on a coat of orange shellac. Over the top of that he applies varnish. Now the question. In a finishing book, that I can’t seem to locate now, the author stated that it is not a good idea to put varnishes or polyurethanes over shellac that has not been dewaxed. Would one of you be so kind as to set me straight. I like the warmth that the orange shellac gives the wood and would like to use it more often.
Jim
Replies
Poly is not a good idea over shellac or anything except poly. it is self sealing. Regular shellac can be top coated with many finishes,,dewaxed is not always a necessity..a lighter cut is generally what is used..say a 1lb. vs. a 3 lb...tho' I have used lacquer over a 3lb. cut with no problems..your results may vary.
Poly will not adhere well to shellac that contains wax. Dewaxed shellac however, makes a fine binder for poly varnish. You can either purchase dewaxed amber or garnet(orange) shellac or mix and dewax your own.
Edited 1/11/2004 10:42:39 PM ET by Howie
Jim,
Well done...Have been thinking about doing this very experiment for some time but never got around to it. I too have been using poly over waxed shellac without problems for years. I agree that there are probably good reasons to use dewaxed shellac versus non-dewaxed, but to say never put poly over de-waxed appears not to be a definent "no-no". There is a show on TV called "Mythbusters",where they recreate situations to prove or disprove generally accepted beliefs of what will happen if certain actions occur. Maybe we could challenge and discuss some long accepted woodworking beliefs and create our own show...maybe call it "Dustbusters". A shop is a terrible thing to waste...
Joe, I always applaud someone who takes the time to test things out.
You followed a pretty standard procedure for adhesion testing except for one thing. The testing standard calls for using a sharp blade tool (like an exacto knife) and cutting 1/4" squares through the layer of finish you are testing. Then, you apply the tape(s) and pull them up. You then count the number of 1/4" sections that have been removed.
I think if you do the test that way you may find a somewhat different result.
In the shop I was involved with, we extensively tested adhesion qualities of finishes for a furniture designer. In our tests, applying an oil based polyurethane varnish over shellac that contained wax clearly resulted in less adhesion. This has been confirmed by at least three polyurethane manufacturers that we dealt with at the time.
Now, maybe the adhesion was good enough but it was not optimum adhesion.
Howie,
When I made the scoring cuts I used a “new” knife blade and cut through to the wood. It’s simple science to know that a coating with some degree of wax contained in it “can” cause an adhesion problem, but shellac (waxed) has always preformed well for me.
One of the “great” strengths of shellac is its ability to sand so well, if you remove the wax you defeat this strength. Besides sanding shellac with 220 or 320 will give the poly an excellent tooth to “adhere” to as well.
Thanks to both you and Dick for commenting.View Image
I believe the author mentions an additive to the dewaxed shellac to improve sanding after dewaxing.
Do you have any experience with the additive? Does it get the sanding qualities back to non-dewaxed shellac after adding?
Jim,
The manufacturers of shellac and polyurethane finishes warn against using shellac that contains wax when topcoating with poly (urethane). Waterborne finishes usually have the same warning. Here's a link to Zinsser's Technical Data Sheet on "Bullseye" shellac (contains wax) - Bullseye Shellac. The warning is on page two in the paragraph "Undercoat for Varnish."
If you're going to use an orange shellac that contains wax, just use a different kind of varnish besides polyurethane. There are a lot of good alkyd and phenolic varnishes on the market and they adhere to shellac with wax without a concern for premature failure.
Paul
It’s this same attitude that prompted me to do the test to begin with. Before I entered into finishing my own work, I had asked an old timer (at the time) what was the best way to “finish” something, anything?
He said to use varnish or polyurethane, there is a difference you know he said. One’s real and one’s synthetic. . . He said you’d what to put a coat or two of shellac on there first, makes for a “sweet” finish, oh and pay no attention to what it says on the can about shellac. . . I think they just want you to use more varnish or poly. . . .
He also said don’t put to much stock into how they (the experts) tell you to put it on either. Slow even stroke, trying not to make to many “air bubbles” in it. . . . . Just slop it on and get the coverage and then “air plane” it. . . Looks like glass after a coat or two. . .
He said the greatest thing to over come in finishing is fear. . . Once you shellac over fear the best thing to do is sand it and then varnish it. . .View Image
Well, I thank everyone. At least I feel better about using varnish or poly over shellac. I think I'll use varnish as Dave Sorg did. I make arts and crafts furniture and have a couple of techniques I want to try first. I just wanted to know because I didn't want water rings on the tops of my tables and plant stands.
Thanks again for the help
Jim
Res,
Your last statement really hits the nail on the head. Its taken me a couple years to have the courage necessary to finish a piece well. Like you, I got my advice from an oldtimer...who would look at me in disgust every time I mentioned something else I had read...(it would have less painfull if he had beat me...lol)
I finally listened...(maybe my wife is right)
Everyone is saying that it is poly that can't be used over dewaxed shellac. Maybe the "old timers" didn't use poly. That said, just use a non-poly varnish. It's a nicer finish anyway.
Gretchen
Edited 1/13/2004 9:07:25 AM ET by GRETCHEN50
The old timer I’m sure used varnish 90% of the time, but I’ve used poly 90% of the time and have never had a failure. . . . How many failures have you had?
For that matter how many people saying "don’t do it", did it and have had a failure? I think most of this information is from people who have never even done it!
Jeff,
I’ve never used an additive in my shellac just plain old shellac straight from the can . . .
Edited 1/13/2004 11:00:23 AM ET by Resurrected
Like you, I got my advice from an oldtimer...who would look at me in disgust every time I mentioned something else I had read...(it would have less painfull if he had beat me...lol)
Long-time finishers are virtually uniform in thinking that nobody (or almost nobody) knows more about their own niche in the finishing universe than they do. That's not to say that your oldtimer friend was wrong. Just that his attitude is absolutely common. And I say that as someone who first started finishing over 20 years ago. ;-)
Regards,
Kevin
The Independent Voter.com
"Rather fail with honor than succeed by fraud" - Sophocles.
Kevin,
That’s a good point, but aren’t most people who do something long enough a certain way of that opinion? Every time in the past that I’ve received advice form people “actually” doing the task their information has been correct. Most people who do things have a tendency to try and do things that work. If the old timer said hey, don’t use shellac under your poly because the stuff will peel off in sheets, I would had take that as fact, but still would have given it a try just to see for myself. . .
It also seems that information “passing” is always of the worst kind when it comes from people with no first hand experience at doing the task they are providing the information for. If someone’s never done it how can they know what will happen and or give advice about it?
Edited 1/13/2004 4:23:50 PM ET by Resurrected
I don't disagree. Perhaps I could have stated my thoughts better by saying that long-time finishers tend (in my experience...) to be more "opinionated" than the average joe/jane. The really good finishers also tend to be very particular, almost to the point of being anal about our craft. In my experience that just enhances the perception that we are "know it alls."
Years ago I quit a painting/finishing job at a custom fixture shop to go work for some friends who had opened up a furniture factory at the same facility that I had first learned to finish at years before - the first company having gone out of business in the meantime. Anyway... some time later I stopped by the custom fixture shop to chat with a few of my old co-workers and see how they were doing. My old supervisor told me (for the first time, mind you) that he had thought that I was an a-hole - his way of saying that I was far too opinionated. Then he conceeded that he'd been wrong. It seems that the finisher who'd taken my place there was the exact same way and he (the old supervisor) had arrived at the conclussion that all finishers are a-holes. Prior to my working there they had never employed a professional, experienced finisher. So, I was their first exposure to professional finishers... until the next guy was hired, that is.
When he told me of his conclussion about finishers I immediately laughed and said that I could have told him that! LOL
FWIW... I wouldn't use poly over shellac that wasn't dewaxed... for the reasons that the manufactorers state. But... I don't use shellac anyway. For sealer type applications that many folks here use Shellac for, I personally prefer to use vinyl sealer for. It doesn't sand as well. But, it's a first-rate moisture barrier. It also works really, really well as a wash sealer.
Regards,
Kevin
The Independent Voter.com
"Rather fail with honor than succeed by fraud" - Sophocles.
Edited 1/13/2004 6:12:49 PM ET by Kevin
Kevin,
I could not agree with you more. Back in '75' to '78' I refinished many pieces and sought the help of someone at work who had been a finisher for one of the big houses here in Boston (Paine's Furniture). He was helpful...but performed much better than he taught...but he did supply me with his own polish and such...which provided great results but not repeatable once I moved to the Midwest...
I’m sure you realize that this isn’t a post about who’s right or wrong, what’s better or not and above all not to disregard manufactures claims and limits they place on their said products. It’s about doing a finishing process that has never showed any of the problems people say it should have.
I make my living by what I do everyday. I have the ability to craft and finish every piece I make and in my small shop simplicity is key. I haven’t used poly in 5 years, but wouldn’t hesitate to put it over a coat of shellac because the many times before I did I never had a problem. . . Maybe I’m lucky, but I doubt it.
As far as “risk” goes I read everyday on the many forums I visit of guys following the instructions to a tee and failing big time. Failure and risk exist at the same end of the scale and the more you gamble the greater the risk. In contrast, the use of shellac has proven its use 100% of the time when used under poly and or varnish and that is far better then any other combination I’ve used in 15 years.
So like I said before, once you shellac over fear, sand it and then poly over it ;-)
and that’s my opinion. . .
Edited 1/13/2004 7:50:29 PM ET by Resurrected
Back in '75' to '78' I refinished many pieces and sought the help of someone at work who had been a finisher for one of the big houses here in Boston (Paine's Furniture). He was helpful...but performed much better than he taught...
You bring up a really good point here. One thing that really bugged me, when I was less experienced, about the real old-timers who had been finishing for seemingly forever was that they didn't like to teach much of anything really useful in terms of their own tricks or techniques. They were always really good at teaching how to sand or wipe stain or basic stuff like that pretty good. But, they always acted as if their main value to the employer was what was in their head... and consequently didn't want to divulge much of it. Apparently they thought that they would be less valuable to the employer if someone else could do what they could.
In all honesty, the number one reason that I joined Knots and continue to post here is to do precisely the opposite of what the old-timers I used to work with did. I enjoy passing on the tricks almost as much as I do the actual finishing. Having someone post here about a struggle with some finishing or painting issue and being able to give them a solution that really works - and them being appreciative of that info... man, that's where it's at for me. I really enjoy that very much. My dad used to be a teacher. Maybe I inherited whatever it is that makes people wanna teach... I dunno. Or maybe I'm just a rebel. LOL
The odd thing with the oldtimers is that once you get to a level where you're approximately their peer in terms of skill they lighten up and start to share their techniques. At least that's been my experience.
Regards,
Kevin
The Independent Voter.com
"Rather fail with honor than succeed by fraud" - Sophocles.
"The manufacturers of shellac and polyurethane finishes warn against using shellac that contains wax when topcoating with poly (urethane). "
Paul,
I'm not disagreeing about the admonition to avoid using waxed shellac - just suggesting we all take the statements of manufacturers with a grain of salt.
As an example, these are the same manufacturers that say their varnishes don't require thinning: this is very likely their way of sidestepping VOC issues and government regulation; In my experience, varnish always applies better when thinned (especially the first coat).
Many manufacturers say things that are self-serving and have no direct bearing on the way their products are used every day in the real world.
Unfortunately, between government regulations and the advice of their insurance companies, many manufacturers are hesitant to provide straight talk for their customers.
PaulWhether you think you can, or you think you can't, you're right.
Paul,
I agree there are times when a manufacturer's guidelines can be modified. Knowing the manufacturer's intent and reasoning is important to making these decisions. The subject of thinning is a prime example; manufacturers have to meet federal guidleines for volatile organic compound emissions as well as the commercial and industrial shops/factories that use the products. Reasonable thinning poses no harm to the performance of the product. Though there are limits and exceptions. For example, waterborne finishes have a thinning limit that when exceeded causes the finish to cease performing properly.
The issue at hand, whether or not to topcoat shellac with wax with a urethane or waterborne finish, is a different animal. The coating chemists that develop these products recognize a real potential for problems. They have made it clear that topcoating waxy shellac with a urethane finish is ill advised. So why do it? I certainly haven't and won't; why take the risk? I make a living doing finishing/refinishing and having to perform re-work due to a mistake I made is a big no-no in my philosophy. Refinishing a piece because I messsed up costs 3 times what it does to do a good finish in the first place.
What seems logical to me may not logical to others and I don't have a problem with that. Knowing the potential for problems and choosing to ignore it is an option everyone has.
Paul
Shellac is one of the kindest, gentlest vinishes ever. It is almost impossible to screw up and easy to fix. It can be placed on top of, or under, vittually any finish known.
Most Shellac flakes for sale are of the de-waxed variety. I wouldn't know why anyone would buy waxed shellac.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
>>Shellac is one of the kindest, gentlest vinishes ever. It is almost impossible to screw up and easy to fix. It can be placed on top of, or under, vittually any finish known.
OK for varnish, lacquer and waterbornes. Not for catalyzed finishes. Every one I have used, whether precat, cat lacquer, or conversion varnish specifically says not to spray over shellac. Vinyl sealer as a bond coat might work.
>>Most Shellac flakes for sale are of the de-waxed variety. I wouldn't know why anyone would buy waxed shellac.
Maybe we're buying different brands, but most of what I get still has the wax in it. The wax occurs naturally in shellac, and dewaxing is another step. When you mix up your shellac and white stuff settles toward the bottom half of the container after a day or so, that's the wax. You can decant the shellac off the top, and for all practical purposes, it's dewaxed.
I agree about its properties, it's beautiful stuff, and far more water resistant than people realize. It just doesn't like alcohol or excessive heat. On the other hand it is really easy to fix. (I did manage to screw it up once or twice.)
Michael R
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