Stupid mistake - polyurethane and lacquer

[Jimmy Nelson]

I've searched this forum up and down regarding finishes, and have learned a lot. I'd like to thank folks like CB and jackthehack for all the information they've posted over the years.
On to my possible stupid mistake...

I'm refinishing my Fender P-Bass. I sanded it down, used Duplicolor primer, then a Duplicolor Truck/SUV/Car lacquer spray paint for blue. I did my coats and let it dry well. I read somewhere on here where somebody recommended the Cabot clear gloss at Lowe's. I decided to go with this. Without thinking about it, I got the polyurethane gloss, since they didn't have a lacquer gloss. I've applied probably 5 or 6 coats of this, until I finally realized that I'm adding a polyurethane finish over a lacquer paint. I've read on here that mixing is sure to screw up the finish.

In my situation, what are my options? Am I making an issue out of nothing? Should I switch to lacquer? Or should I sand it back and start over and use lacquer only?

 

[Mor Paul]

Wait.

If it gets messed up, start over, I guess. If it doesn't, you might be good.

 

[tfarny]

Wait a week and see if something bad happens before sanding it all off.

 

[Tonar8352]

Poly over lacquer is ok, lacquer over poly won’t work because the thinners are to hot and they will melt the poly.

 

[Jimmy Nelson]

Is this polyurethane spray too soft of a finish for necks and bodies? I read this from =CB= on here. I don't want to keep applying this stuff if I'm only about to find out it's a bad idea... I got a new neck for a strat build and I've already done 4-5 coats.

 

[jackthehack]

Is this polyurethane spray too soft of a finish for necks and bodies? I read this from =CB= on here. I don't want to keep applying this stuff if I'm only about to find out it's a bad idea... I got a new neck for a strat build and I've already done 4-5 coats.

You're kind of stuck now unless you want to sand it all the way down and start over. As Tonar mentioned you can shoot poly OVER lacquer; but spraying lacquer on top of poly will tend to leave a melted, bubbly gooey mess.

Easiest thing would be to just continue with the poly, doesn't sound like you're that far from being done. The vast majority of store-bought guitars come with poly finishes, I wouldn't worry about "soft"; from my experience it's just as easy, if not easier to chip off lacquer....

 

[dmraco]

Is this polyurethane spray too soft of a finish for necks and bodies? I read this from =CB= on here. I don't want to keep applying this stuff if I'm only about to find out it's a bad idea... I got a new neck for a strat build and I've already done 4-5 coats.

I have a minwax poly tele I did YEARS AGO...it was so long ago I ordered the parts over the phone from a green WARMOTH book that had been stapled together.  I would say it is about 15 years old...no issues at all.  The poly has even aged to a nice amber on the neck.  No signs of year.

 

[Jimmy Nelson]

Cool. Sounds like I shouldn't worry about the new neck with polyurethane gloss...

But back to my P Bass body with the poly gloss over lacquer paint... Even after 5-6 coats, it doesn't seem glossy at all... In fact, it looks the same. Almost as if the lacquer has a shield that makes the poly bounce off of it. It makes me want to try to continue it with lacquer gloss... If it screws the finish, I could always strip and sand down right?

How hard is it to strip this down and get it ready to redo? I already have a paint/lacquer stripper from Lowe's. It really wouldn't cost me much money I know... Just time. The good thing I would get out of it by sanding it down, is doing a better job at getting rid of the nicks/bumps this time.

Thanks for the advice from everybody...

 

[dmraco]

post a pic.  If it does not have the look you want...sand it off.

I have found you need a good 8-10 cost of poly to get a good shine.  So ask your self...should you continue?

 

[Mor Paul]

That's really odd. A fine sanding/polishing might help, but you might want it to really harden first.

 

[Jimmy Nelson]

Check 1, 2.

 

[rbwalter]

Have you tried automotive rubbing compound?  After it dries, that's the last step in really shining it up.  Also, it looks like you have some "blush" on the back (unless it's just the lighting).  I painted a body last year and I really struggled with that because my garage was so humid. 

 

[-CB-]

Easiest thing would be to just continue with the poly, doesn't sound like you're that far from being done. The vast majority of store-bought guitars come with poly finishes, I wouldn't worry about "soft"; from my experience it's just as easy, if not easier to chip off lacquer....

I agree with what Jack said - just keep going and see how it turns out, but.....

The part about "the majority of store bought guitars come with poly finishes and softness has some things to be examined.

Rattle can "polyurethane" finishes are soft.  They are an air dry finish.

Store bought guitars have a 2-part finish, a sort of epoxy finish that is also a poly urethane.  These are catalyst harden finishes, and are very hard compared to rattle can poly's.

Come to think of it, you can get spray on FOAM polyurethane.  You can get polyurethane bushings (for suspension parts and motor mounts) which act like super rubber.

There are countless types of materials that chemically classify as poly-urethane products.  They are all different.  So you cant really classify a 2-part epoxy urethane finish the same as a rattle can polyurethane finish - they be different animules.

Everything else Jack said is +1 spot on.

 

[Jimmy Nelson]

I've seen in some of jackthehack's posts where he talks about doing the finish with the clear coats, then playing the guitar for a while, then disassembling a month later to do the final wet sand/polish. I'm wondering how long I should wait after my last clear coat until I could assemble it back together for the time being.

I've done probably 10 coats of clear lacquer gloss (deft) on my strat, with a day or two between each coat. Do you think in another day or so I could assemble, play it for a while, then later do the finishing touches (after fully hardens). I just don't want to end up making the pickguard stick to the body and the bridge as well. It doesn't seem gummy at all though, considering I was pretty good with doing thin coats.

I got 600 grit wet/dry paper and that green turtle wax that comes with the pad thing to spread and rub. Is this where I'll get the glass-like coat from? The lacquer clear coats don't seem super glossy or shiny... Not that that's a bad thing. I just want to know for sure that I've done enough coats, so I'm applying turtle wax over clear coat, not the wood itself. By the way, it's an alder strat body, with a water-based minwax stain. Thanks for any help.

 

[jackthehack]

There's a lot of variables involved here so it's pretty hard to state empirically you need to wait X days or that you have to do X number of coats as temperature/humidity/environment all effect lacquer drying times and nobody probably applies coats in the exact same thickness. You can't always judge lacquer at all by touch, I've screwed up a number of times trying to do final finishing too soon; the surface seems completely dry but there are layers underneath that haven't dried out yet...

Another big differential is wood types; you may often think you're done, but after a few weeks/months the lacquer may continue to dry/cure/shrink; all those pores you thought were completely filled turn out not to be.... Your axe being alder this is much less likely to be an issue.

10 coats could be enough. Wait 3-5 days after final coat before assembling, if you have a pickguard don't torque the screws putting it in, just enough to seat the pickguard. Then you can go ahead and play it, and how long you wait to disassemble and do final leveling/wet sanding can again be dependant on conditions.

I do find your description curious; I've always used StewMac or Deft rattle can lacquer and while not "mirror-like" before final leveling/wet-sanding/polishing, it SHOULD look shiny; maybe this is totally semantical; can you take a couple pics in the sun or a good light source so we can see what you mean?

 

[Jimmy Nelson]

http://i174.photobucket.com/albums/w120/eddiesatan/DSC01806.jpg

http://i174.photobucket.com/albums/w120/eddiesatan/DSC01823.jpg

 

[Mor Paul]

If you've got enough layers, I think you might need to sand smooth, then polish. Let's wait for Jack, CB, Tonar, or someone else, though

 

[-CB-]

Most finishes dont go down totally gloss and smooth.  Most have some texture.  That texture needs to be sanded smooth, then buffed out to re-establish the gloss.  The fly-in-the-ointment is: Can you sand the finish?

Some finishes are glossy, but sticky and cant be sanded.  Some are glossy but sand to a dust like residue - very hard finish.  A hard finish is preferred, because it sands out and buffs out well.  Nearly effortless so.  Its those sticky gummy finishes that give you grief and make you lube the sandpaper and all sorts of other nasty and unmentionable things.

If you can sand it, it'll be ok.  Try someplace - lightly - that wont show (under the pick guard).  Use some 400 grit wet with a little soapy water.  If it sands clean, keep on going to get the texture flat.  Then you can go with something like 600 or 800 paper, also wet.  Auto compound will take out 600 grit sanding, but some folks like to go 1500 grit if they have heavy handed the 600 grit.  I usually stop at 600 then rub it out with compound, followed by a swirl removing wax.  Turtlewax has products that do that - apt for a Warmoth, no?

 

[SimsCustomShop]

Poly over lacquer is ok, lacquer over poly won’t work because the thinners are to hot and they will melt the poly.

You got it backwards. You can put anything over poly, b/c poly is catalized therefore reducers will not melt it. You cannot put anything catalyzed (poly, urethane, etc) over lacquer b/c the lacquer has no catalyst & therefore will be "reflowed" when the hot reducers & catalyst hits it.....resulting in a list of potential problems.

If I were you I wouldn't even waste my time sanding. I would grab a rag & some lacquer thinner, wipe it all off & start over....& use the correct clear coat this time.

 

[-CB-]

Again, there is poly, and there is poly, and yet again, poly.

For the sake of being redundant - one more time - not all "poly" is the same.

Some poly can be reflowed!  Some changes state in air and cant really be "reflowed" but will craze with acetone (ie, lacquer thinner).  Some is a catalyzed epoxy and about the only thing that hits it (if at all) is methyl chloride, or some variant thereof.

Ok, so where does all this information fit in the picture, and how does it effect Uncle Oscar (the Grouch) in his garbage can?  Well, its like this:  TEST, and if in doubt, RE-TEST.

Is it all that hard to test a little in a place that wont ever show, or.... on a scrap (if you started the whole finish yourself).

Nothing touches Fender's "poly" finish.  Warmoths is similarly... pretty tough stuff.  Lacquer goes over it ok.  However, the rule of thumb... depends on who you talk to.  Some poly goes over lacquer.  Lacquer goes over some poly - but not the same poly that will go over lacquer.  Hmm.  Lacquer goes over shellac and vice versa, pretty well.  Poly goes over shellac, usually.  But... BUT... do a test... its not hard, it takes some time, yes... but its worth it to not screw up a finish.