Blushing? (lacquer content)

[txspreacher]

I generally use wipe-on finishes for necks, but have one I'm spraying lacquer on. I have the headstock finished and it's ready to wetsand/polish. One problem. I'm one of those types that says "just a little more" and then wishes I hadn't. I hit the last coat and it fogged up on me. I've read a few different methods of removing this - from sanding, to wiping down with thiner, to using blush eraser. My instinct is to simply sand past that last coat. What do some of you other folks do when this happens?

[joemac]

Lightly sand it with 600 grit and polish.
I'm assuming you want a gloss finish.

[GUITARmole]

I usually take it inside to hang in a closet and cure overnight (where the humidity is more controlled...assuming you're painting in your garage or shop) and when I wake up the next morning the blushing is usually gone. If it isn't, many times you can just hit it with another coat of clear and it will remelt the top layer and let the moisture escape (getting rid of the blushing). Sanding w/ some mineral spirits might help too.

[GTO]

Unless you have been spraying in a thunderstorm blush is only in the first few microns of the surface, and unless you have left the paint to dry is solved by another immediate coat of paint/lacquer, providing you can quickly get some heat set up to flash off the paint and stop it happening again.

Otherwise blush eraser is best if the surface has dried. And if you are painting in a humid atmosphere some heat and perhaps using some anti-blush thinners for the next coats. Don't wipe thinners on, it will be like wiping a rag through treacle and you will ruin the finish you already have. Neither would I sand it as, if you think about it, after the first cut of the paper (hopefully finer than 600 grit), how do you know if you have removed all the blush or not?

[blue moon]

I had a similar problem on a body I was painting one humid summer. It blushed so bad I was afraid I was going to have to strip it and start all over. I ordered a can of blush remover from Stew-Mac and it saved the day. All the blushing disappeared right away. It's a little pricey at $10.00 a can plus shipping but it sure does the job. I understand that ReRanch now sell blush eraser but have no experience with theirs.

[txspreacher]

Better late than never, I guess. Thanks for the replies, folks!

It never cleared up hanging in the closet, and that last coat ws probably more than I needed anyway. I wetsanded starting at 600 and it was gone quickly. Thanks again.

[Rhomco Guitars]

Where are you located? DFW? If so, I keep plenty of nitrocellulose lacquer supplies on hand for all the finishing work I do. Blush eraser is a staple in my final finishes. Using it for the final clear coat/s after wet sanding will look darn near buffed!
Coffee, Sand Paper & Lacquer Fumes..... now thats a weekend!
Rob

[txspreacher]

Originally Posted by rhomco

Coffee, Sand Paper & Lacquer Fumes..... now thats a weekend!
Rob

HAHAHA!!!!! That's exactly what was going on when I was finishing the headstock this weekend! I'm doing the rest of the neck now and have two bodies to paint and it will likely be muggy as all get-out when I finally have time to shoot them.

Yep, I'm in the DFW area these days....Lake Ray Hubbard area.

[Melody]

I love happy endings!

[TRexF16]

Originally Posted by GUITARmole

I usually take it inside to hang in a closet and cure overnight (where the humidity is more controlled...assuming you're painting in your garage or shop) and when I wake up the next morning the blushing is usually gone. If it isn't, many times you can just hit it with another coat of clear and it will remelt the top layer and let the moisture escape (getting rid of the blushing). Sanding w/ some mineral spirits might help too.

Thanks GUITARmole! This just worked like a champ for me. Blush looked aweful and I was freaking out (first build). The blush began to disappear while drying, and soon as I hit it with another light coat of clear after a couple hours (Watco rattle can) it vanished.

Whew!

Rex

[thefees]

Had a body shop for 20 years. Did more high end cars with lacquers back then before they took the lead out. More than I care to imagine. By the way lacquers will never polish the way urethanes do because they removed the lead, and there went the gloss.

Gibson creates gloss on thier instruments over lacquer by polishing wax into the instrument. You can just do the wax step if you want on a glass smooth piece of wood and get the same gloss. Gibson needs to add color so they spray with lacquer.

On cars you NEVER put a coat of wax on a car until the lacquer cured for at least 6 weeks outside preferably in the sun. Otherwise you are trapping solvents and blushing, or dulling the surface. I used to have people come back in about 4 weeks to have the car top polished after it fully cured. It looked like gold when it went out the door, but all that curing required a little topping up. Of course the customer adding wax after full cure was the final steps.

With guitars being made out of wood, there is another exit route for the vapors to escape in, that is internally. Still not an ideal scenario, and that is why Gibson LP's for example, although the wax shines, it still doesn't have the mile deep polished gloss, especially over time. They look great so don't write me thinking I am putting them down, I have an 95 Epi LP that looks great.

Anyhow, onto your blush problem. As we all know blushing in lacquers is because moisture from the air is being trapped. So how to deal with it, and how to prevent it.

Best thing is to spray on a low humidity day. Rainy days are worst. Use a higher quality slower drying thinner. The only time you have a problem with refinishing is when you rush it. A lot of thin coats are better than one thick one. Thin coats allows the moisture to escape. Lacquers cure by releasing vapors, urethanes cure internally.

Now onto the repair of a blushed cured finish. You're screwed. You have to sand down through it, not through to the wood perse but deep enough to get the blush out. Then you can recoat it, and be sure to put some retarder in with the mix. The reason why I said you are screwed is if you didn't put enough non blushing finish on it before the blush coat, and you sand down through the clear all the way to the wood, you will most likely have a breakthrough spot that will show no matter what you do. I am talking clear coats here. If it is a color then that doesn't apply, and you can top coat it and it won't show. (Other than a possible ring that you can 600 grit out)

Lacquers with hardeners give you much better results, but none of them will touch the look and chemical resistance, and durability of a urethane with hardener. Air dry urethanes are too soft to buff. Two part urethanes are expensive as all get out, but if you use them, the best time to buff is the following day. They will give you mind blowing results. Hope this helps.

By the way the blush you think you sanded out, and topped with wax to look real good comes back unless it is all removed. Give it a month to find out. Maybe it won't come back enough to bother you, and maybe it will. It all depends on whether you sanded all of the blushed material out. One way to help remove blush in lacquer during application is to do the last coat with more retarder slowing the cure down sufficiently to let the moisture escape.

Hey chances are you got it all, and everything will be fine. I don't mean to put a damper on your lacquer. (No pun intended) I am relating this to a car though with a lot of coats on it; sufficient in numbers to be able to sand it smooth as a chalkboard, and then compound/buff all of the sanding scratches out, yes like you do in guitars for that bench buffing machine mile deep gloss, the way Fender does with urethanes.