Nitro finish ruined with acetone cleaning. What to do now ?

[nic'o'caster]

Thank you all for your support, advice and humor !
I'll try the DIY method first (800-1500 wet sanding then machine buffing) when I get time. I don't need the exact replica of the original finish, just want to smooth things out.

Nice story robt57 it reminds me of this one :

 

[BopT]

I would get out the 1000-2000 grit and wet sand the area. Just go over it while watching a football game or better yet baseball. The area should look pretty even and you have learned the lesson that you only put stickers on bass guitars.

 

[R. Stratenstein]

I hope it is not too late, but do NOT sand anything yet. Order a can of Blush Eraser from StewMac or where ever else you want to. Take off the hardware pickups and everything else that's not lacquered wood. Lay the guitar flat on its back and spray on the Blush eraser generously, but avoid runs down the sides. Unless you've managed to rub off all your clearcoat with the acetone, the Blush Eraser will flow out the lacquer that is there. If the first application seems to help, do more coats. Then decide if you want to level sand and buff. If it doesn't work, you were screwed anyway, and feel free to apply more stickers, sand it, or attack it with a chain saw. It's going to néed refinishing.

BTW, Blush Eraser is full of bad stuff, (like acetone!) so only spray it in a safe place, and use a respirator. A cheap respirator from Homer Depot or Harbor Freight is fine, so long as it's rated for organic solvents.

 

[robt57]

I never used blush remover. I have thinned heavily and laid a layer to level out peal. Then I got a gun that work so well for me I usually do not block/wet sand. Just hand polish with some airplane polishes I have left over from those days.

Example, and on pine too. not perfectly level, but lots of time save on wet/block sanding too [call me lazy, it was a free bee for a friend]:


Prior to hand polish:

After hand polish, and quick one at that.

 

[R. Stratenstein]

Yup, well tuned gun, proper nitro thin ratio, and experienced operator--magic! The finisher at Heritage Guitars told me if they have to level sand one, somebody (usually him) made a boo-boo. They go from clear to polish/buff.

However, for those sub-mortals like most of us in the unwashed masses, a little help is needed from time to time, and Blush Eraser is one of those little helpers that can, obviously, help get rid of blush problems when you have to shoot when it's more humid than you'd like, but also, it's re-flowing properties have the magic effect of knocking down orange peel, and flowing out scratches and damage like our OP suffered--if he's lucky. I don't think it has much more than lacquer thinner and retarder in it, but it does what it advertises, and also levels out nitro finishes.

Nice paint job, BTW. I need to get me a good spray rig like yours.

 

[old_picker]

as soon as you start taking material off by sanding you'll be in trouble. My advice is to get some rattle can nitro and over spray many coats over the front face of the guitar. As you spray the part that has been destroyed will start self levelling. Once you have a decent thickness block level and buff it out.

 

[Tony Done]

as soon as you start taking material off by sanding you'll be in trouble. My advice is to get some rattle can nitro and over spray many coats over the front face of the guitar. As you spray the part that has been destroyed will start self levelling. Once you have a decent thickness block level and buff it out.

I like that. Rattlecan nitro is hard to get here, so I did a decent job of overspraying/levelling a Gibson headstock using a Preval and diluted nail varnish.

 

[robt57]

Nice paint job, BTW. I need to get me a good spray rig like yours.

Thanks, good thing it has only an 8oz can. Keeps me honest, and near zero runs even in greedy mode. I have always put on as much material as I can when painting, and let the levelers do what they are supposed to do. Being a GC for a few decades probably helped. When I do drip, I go large though...

I think it is just a Husky detail siphon gun. I have had it for forever.

When I spray a few at a time it does get tiresome with the 8oz can.

 

[nic'o'caster]

Wait, you mean I just spray a bit of that on the ruined area and it will just melt the nitro finish back to super flat and shiny, like magic !!???
image removed

 

[moosie]

Wait, you mean I just spray a bit of that on the ruined area and it will just melt the nitro finish back to super flat and shiny, like magic !!???
image removed

Conceptually, yes. But pay attention to the details of what the person recommending it advised, or you could be worse off than when you started.

One of the great properties of nitro lacquer is it's ability to be reworked.

 

[robt57]

using a Preval and diluted nail varnish.

Diluted? Alcohol, I am thinking??

 

[Tony Done]

Diluted? Alcohol, I am thinking??

I can't remember, it was a long time ago. It wouldn't have been alcohol, as that is incompatible, most likely it was nail varnish remover. OTOH, I might have done a bit of google research on nitro thinners.

Something that might be of interest. One of the coats in my project fogged up very badly, like white paint, through doing it on a too-damp day. Denatured alcohol cleared it OK, no problem.

 

[robt57]

I was thinking shellac. Varnish uses paint thinner / mineral spirits apparently [google]

 

[old_picker]

I like that. Rattlecan nitro is hard to get here, so I did a decent job of overspraying/levelling a Gibson headstock using a Preval and diluted nail varnish.

well no it's not:
https://www.guitaraust.com.au/finishing/aerosols.html?___SID=U
ask Nello nicely and she'll send it up by road using australia post - you'll have it in a few days

 

[Tony Done]

I was thinking shellac. Varnish uses paint thinner / mineral spirits apparently [google]

Yes, shellac dissolves in alcohol. One of its attactrions is very fast drying to a

well no it's not:
https://www.guitaraust.com.au/finishing/aerosols.html?___SID=U
ask Nello nicely and she'll send it up by road using australia post - you'll have it in a few days

Thanks. Is that fairly recent, ie the past year or two? Last time I looked, unsuccessfully, was a while back.

 

[old_picker]

at least two years i reckon

 

[R. Stratenstein]

Nail polish and nitro lacquer are first cousins, usually. They both are highly soluble in acetone. Shellac is alcohol soluble, and they are not compatible. I'm guessing the denatured alcohol drew the moisture out of Tony's fogged paint job, but you can't depend on that, if the lacquer surface has hardened, alcohol won't work on it. Anyway, that's a different problem than the OP ihas.

Reshooting the cleatcoat will work, but will require more skill than reflowing what's there with Blush Eraser.

 

[Musekatcher]

Wait, you mean I just spray a bit of that on the ruined area and it will just melt the nitro finish back to super flat and shiny, like magic !!???

DONT sand yet. The above product is new to me but, I've fixed marred shellac, varnish and lacquer finishes with high content rubbing alcohol. You need to remove everything, and start with a heavy smooth cloth dabbed with alcohol, and work the entire front so it all blends as you "augment" the finish. As you work in long straight strokes, you can feel the softening and re-hardening of the finish, and adjust the pressure and speed to get a nice hand-rubbed finish.

If that doesn't work, go back to the original chemical you used, acetone, and dilute it to half strength, and try working the entire top with it as well. If that doesn't smooth it out enough for you, then go to the sandpaper and re-shoot. You can try hand-rubbing it after that with alchohol or acetone DILUTED to blend it as perfect as you like.

 

[Musekatcher]

Nail polish and nitro lacquer are first cousins, usually. They both are highly soluble in acetone. Shellac is alcohol soluble, and they are not compatible. I'm guessing the denatured alcohol drew the moisture out of Tony's fogged paint job, but you can't depend on that, if the lacquer surface has hardened, alcohol won't work on it. Anyway, that's a different problem than the OP ihas.

Reshooting the cleatcoat will work, but will require more skill than reflowing what's there with Blush Eraser.

Re-flowing, is what I was describing in my post above -

 

[Vizcaster]

If you're shooting nitrocellulose lacquer in a Preval, you may need to thin it with proper lacquer thinner, which really should be something labeled by the same company who made the lacquer (sometimes they call it "reducer") because it's a mix of solvents. Unfortunately the stuff at the paint store in big cans that say "lacquer thinner" is a cheaper mix (by the way acetone is one of the main ingredients).

If you can get lacquer in a spray can, by all means give it a try. Although spray cans are expensive ounce-for-ounce, you don't have the investment in a quantity you don't need (lacquer sells by the quart, same for the reducer, then there's the preval aerosol engines, so it adds up).

However you spray the lacquer, it will melt the existing finish, a feature called "burn in." Then after the new finish is cured for a few weeks (don't rush) you can sand it level and buff it out. Rather than a hardware store, you might find a better selection of very fine sandpaper and buffing compounds in the paint aisle at the auto parts store (or a woodworking catalog).

What you're doing is called a "spot repair" and it's usually invisible when you're done. Because of the "burn in" the lacquer will not reveal any witness lines when you sand it level (other finishes such as varnish would show where the new and old layers are in lines that look like a topographic map when you try to sand them). Years from now the nitro may shrink back unevenly and reveal the repair, but you shouldn't worry about that yet.