Behlen adhesion problems...

Matt Clara

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After allowing my latest build to cure for 16 days, I sanded to 1500 grit and polished with the ColorTone medium and fine polishing compounds, so it was looking pretty good. Then I went to scrape out the bridge area for gluing, only to find the finish is peeling up rather than scraping, so I stopped and scored the edges of the area I wanted to scrape for the bridge with a razor, only to find that caused the finish to lift up around the score mark, too. I might have been able to ignore it (denial), but the bubble of the lifted area extended outside of my 1/16" safety zone I left in the finish to go under the bridge, so now it's screwed up entirely, in my opinion. I suppose I could build a larger bridge to cover it, but my fear is this will only get worse. Of all the things I could have done wrong to cause an adhesion problem I come back to these two:


  1. should have used Behlen's own thinner/reducer instead of the Crown Lacquer thinner I bought at a local Woodcraft store.
  2. because I thinned the Behlen vinyl sealer, I should have shot more than one coat.

Any opinions there?
 
I'm a believer in a quick few coats of french polish over raw wood/epoxy filled. I don't know anything about crown thinner but a do believe a lower grade thinner could be the culprit.
 
shellac sealer + Cardinal nitro Or, shellac sealer anyway. Shellac adheres to anything (maybe not a candle) and anything sticks to shellac.
 
I'm a believer in a quick few coats of french polish over raw wood/epoxy filled. I don't know anything about crown thinner but a do believe a lower grade thinner could be the culprit.

Poor adhesion is a nightmare, not only for what you are experiencing now but later on down the road as well. During it's life time, every little bump on the edge or corner of the uke will turn white as the lacquer separates from the wood. When testing new lacquers, fillers and sealers I always test for adhesion first. Test. Test. Test.
Always use the same brand thinner and retarder as the lacquer. It's doubtful though that that would give you such an extreme adhesion problem. My guess is that it's whatever you are applying between the wood and your lacquer. The only time I've run into an adhesion problem with Behlens was when applying it over epoxy pore filler. If you are using an epoxy filler make sure it is fully cure, perhaps up to 72 hours.
Why are you using vinyl sealer? I'm not sure it has any positive effect as an instrument coating. It may help to fill minor imperfections but at the cost of leaving a rather soft coat between your wood and the lacquer. I'm convinced it doesn't help the lacquer stick any better. I stopped using it years ago.
Try shellac as a sealer. It'll stick to anything and anything will stick to it.
Also, for lacquer finishes I stop sanding the pore filler at 200 grit. It allows for a nice mechanical bond, anything 400 or higher and you lose that.
Finally, others may disagree with me but there are better lacquers than Behlens' (Mohawk.) (I'm biting my tongue here so hard it's bleeding!) I can't tell you how many times I've almost quit building over my frustration with that stuff. Check out Cardinal. You'll be glad you did.

EDIT**** Chris beat me to it while I was typing. Chris knows finishes.
 
if you can remove the neck, acetone will quickly remove the lacquer on your instrument, so you can finish it again. Keep changing rags until it wipes without drag. Careful if you have any CA near the surface, as acetone can eat that away. Otherwise, as Chuck said, this is the beginning of the ugly. Wipe it clean until you have it all gone, maybe a light sand to ensure it is gone, but protecting your grain fill, and then a couple light coats of shellac. There are lots of different lacquers that people use. Cardinal works great. For me, the search ends there, I am happy with it until they mess it up with a formulation change, or it becomes unavailable. Why Behlens? I cannot think of any reason.
 
I use shellac under my Oil Varnish as well. It makes a HUGE difference. Actually, I currently use Zinsser "sealcoat", which is alcohol based and has absolutely no wax in it, unlike their "shellac", which does, and you DON'T want wax.
 
Thanks guys. I am finishing over zpoxy epoxy used as a grain filler. I'm pretty sure I gave it ample time to cure, but I can't recall exactly. Chuck, the Behlen Stringed Instrument Lacquer instructions say to apply the vinyl sealer as the base coat to insure adhesion. I think I'll try the Cardinal, but I may try the Sherwin Williams as we have three or four SW stores here where I live, including one main distribution center. I spent $900+ with them last summer on paint for my house, so I already have an account there.
 
I have an account at the local paint store too. Lacquer there cost about half of what it cost me for Cardinal. Doesn't tempt me for a millisecond, to use on an uke. Even in a bind. My labor is what is precious to me in building something, and finishing it, not the cost of the finish. With so many massively skilled people recommending Cardinal, why would you re-invent the wheel. If you happen to discover another brand, and it works for you, then great.

Sealcoat is good, but the wax in shellac will cause you no problems with nitro, or varnish. The only problem I have ever had with shellac, was early on, applying too much, or not letting it cure sufficiently before top coating with lacquer. About a year later I could see a slight 'alligatoring' due to the shellac shrinking under the lacquer. A couple thin coats of shellac, with sanding, let it cure, and you are good to go. Oh, and I guess some fisheyes when sharing gear and not cleaning sufficiently after spraying shellac. (flushing plenty with the solvent used for the lacquer, before loading the gun with strained finish.
 
Chuck, the Behlen Stringed Instrument Lacquer instructions say to apply the vinyl sealer as the base coat to insure adhesion. .

Yep, I blindly followed that advice for years as well. What I've come to learn is that we, as builders, have far more practical experience in our particular field than coating salesmen or their tech guys do. Vinyl sealer does give you a smoother finish because it fills micro imperfections, but my own personal experience has proven to me that it does nothing to aid in adhesion. (I'm sure I'm mistaken but I'm guessing it's only lacquer with some talc added.) Follow the advice you've gotten here and you won't go wrong.
BTW, I've been using the same shellac as Bruce mentioned. You want the "Seal Coat" (100% wax-free), comes in quart cans, use with a good shellac brush). My Internet research has shown that the Bull's Eye shellac in the spray can is also wax free even do it doesn't say so on the can. But I dunno. Test!
 
Thank you Chuck, I will do that. I will likely follow Chris's advice to strip the current finish, too, even though it kills me to do so!
 
The one reason I can say why not to Behlen, albeit maybe not the best reason, is that I have read peoples opinions that it is a poor lacquer. I have sprayed a lot of lacquer, (in the low thousands of gallons) I have used a number of brands, but when I found something that worked, I stuck with it, for predictable results. When paint companies change formulae, or go out of business, stores change their lines, or I move, a few times I have been left looking. Not all lacquers are created equal. I read opinions that Cardinal is great lacquer, I tried it, confirmed it. It is not the easiest lacquer I have sprayed, but it is not difficult. It is the most durable nitrocellulose lacquer I have used, it polishes beautifully, repairs easily, it is just a great finish. I love how it feels. When I hear a voice of someone with great experience who tells me that Behlen's lacquer sucks. All I need to hear it is once. Currently, you are feeling frustration with a failed finish? If you had used a different set of products, it is likely that you would not be having the problem that you are. While it is possible or maybe even likely that your issue is not due to the products used, I can add that to my reasons why not to use that brand. I am not intending to pick bones with you... just sharing my experience.

And, while I do shop at Woodcraft, I consider it a DIY store. While they sell some nice stuff, their overall stance seems aimed at the weekend warrior. Sometimes they have cool wood, and there are some odds and ends that I buy there.
 
Thank you Chuck, I will do that. I will likely follow Chris's advice to strip the current finish, too, even though it kills me to do so!

It should kill you not to. It'll take an hour to strip and and you'll lose the time you have already got into it. But the uke will probably outlast you and it's what you'll leave behind! Make it the best you can.
Strip it. Shellac. Better lacquer. And wait a few weeks or longer before sanding/buffing.
 
The one reason I can say why not to Behlen, albeit maybe not the best reason, is that I have read peoples opinions that it is a poor lacquer. I have sprayed a lot of lacquer, (in the low thousands of gallons) I have used a number of brands, but when I found something that worked, I stuck with it, for predictable results. When paint companies change formulae, or go out of business, stores change their lines, or I move, a few times I have been left looking. Not all lacquers are created equal. I read opinions that Cardinal is great lacquer, I tried it, confirmed it. It is not the easiest lacquer I have sprayed, but it is not difficult. It is the most durable nitrocellulose lacquer I have used, it polishes beautifully, repairs easily, it is just a great finish. I love how it feels. When I hear a voice of someone with great experience who tells me that Behlen's lacquer sucks. All I need to hear it is once. Currently, you are feeling frustration with a failed finish? If you had used a different set of products, it is likely that you would not be having the problem that you are. While it is possible or maybe even likely that your issue is not due to the products used, I can add that to my reasons why not to use that brand. I am not intending to pick bones with you... just sharing my experience.

And, while I do shop at Woodcraft, I consider it a DIY store. While they sell some nice stuff, their overall stance seems aimed at the weekend warrior. Sometimes they have cool wood, and there are some odds and ends that I buy there.

Thanks Chris, I appreciate the information you've given me. Technically I don't shop at Woodcraft, but at a cool lumberyard that stocks tons of exotic wood (and I do mean tons), high-end tools (that I can't afford), and they also have some kind of deal with Woodcraft allowing them to stock many of their products, including the full Behlen lineup. I do try to save a buck when I can as I'm a single dad on a budget, and I doubt the adhesion failure I'm experiencing can be directly attributable to the Behlen products, or StewMac and LMI wouldn't carry them, but regardless the cause, I'm not likely to use it again.
 
It should kill you not to. It'll take an hour to strip and and you'll lose the time you have already got into it. But the uke will probably outlast you and it's what you'll leave behind! Make it the best you can.
Strip it. Shellac. Better lacquer. And wait a few weeks or longer before sanding/buffing.

Yeah, it's killing me either way. This was/is my "back in the saddle" build, so I wasn't overly concerned about some small imperfections (good thing, too, 'cause they're there!). This goes beyond that, though, obviously.
 
Yeah, it's killing me either way. This was/is my "back in the saddle" build, so I wasn't overly concerned about some small imperfections (good thing, too, 'cause they're there!). This goes beyond that, though, obviously.

Dust off your spurs and climb back on. Other problems you can have with extremely poor adhesion will show up will show up when you are removing the tape from the fret board or start working around the fret ends and nut slot. If you tighten your turners a hair to much the lacquer will release from the wood causing an ugly while halo. Same thing when drilling holes for pickups or strap pins. Don't try to work around an adhesion problem, fix it.
 
Moore Bettah Ukuleles;1499304 My Internet research has shown that the Bull's Eye shellac in the spray can is also wax free even do it doesn't say so on the can. But I dunno. Test![/QUOTE said:
The bulls eye spray can i have in my hand says "spray shellac is 100% wax free" However I looked at the big tin at homedepo and it didn't say anything about being wax free.
 
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