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I’ve been spraying nitro lacquer on my first acoustic build (I’m in the North east so I take it out in my garage, warm up the can, spray the guitar, then bring the guitar inside for drying).

At about the 6th-7th coat I started wet sanding to level things out a bit and I noticed what I believe was some blushing (See picture). I let it sit for a few days and it didn’t seem to go away, so I purchased some blush retarder from Stewmac after reading the reviews.

Well, I think things are getting a little better after a coat, but the blush retarder came out of the aerosol can a little heavier and I got some runs. I level sanded a bit, then sprayed nitro over it, but there still seems to be a very visible mark (See second picture).

I guess I was hoping that would blend in with the additional coats of Nitro that I was planning on spraying on top.

So anyway, I’ve sprayed a few more coats of Nitro and the blushing is coming back and the retarder run is very visible still.

So what would you advise I do? Should I keep spraying the retarder and hope it clears up? Should I sand back down to get rid of the run from the retarder? Is that in fact blushing? Any advice is welcome. Thanks!

take some thinner and paint it on there. If your using rattle cans you have to be careful too close you get micro bubbles that is what it looks like you have. if you can't get it out sand back start over

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Once you spray a coat of lacquer over top of the blushed area you bury it under finish and need to sand back until you remove the blushing.
I would sand those areas to remove the blushing on the side and the area on the back until you have a smooth unblushed surface. You don't have to take it back to wood unless the finish underneath the blushing is completely messed up.
When I spray in cold conditions that can cause blushing, immediately after spraying I will move the object to a warm room and put it under incandescent lights . The lower humidity in the room and heat from the lights help drive off the moisture that causes blushing. Retarder is not a panacea for all situations causing blushing and if used too heavily causes its own problems. Blushing is usually at the surface and often a light sanding after the finish has dried will remove it. I do that in preference to using retarder most of the time.

My best advice is to take the current finish off and try again. You've got a mess going on and it will be easier to start over than try and salvage acceptably.

If you must move the guitar in and out like that you will have to wait for better weather as that is the root cause of your issue.... The rapidly changing temps and rh from the house to garage and back cause condensation like a sweaty toilet tank, just not that bad. This draws moisture in as solvents evaporate. The warmed lacquer shot through cold damp air is pulling in moisture to compounding the issue.

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

That looks more like dry spray than blushing. When you spray you want to get a full wet coat over the entire surface.

And that run is really nothing. A good wet coat on top of it would make it practically disappear.

I have to agree to start over. I suspect your gun set up.
what mix are you using? Thinner ratio , and retarder?

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I agree, sand back. If it were only on the back, u could sand just the back as u are using nitro. Won’t take more than 30 minutes. If u did epoxy pore fill, do a wash coat again, let cure over night.

John, what ratio of nitro/thinner/retarder do you use?

After looking at pics again, I don’t see any pore fill. Could this be some kind of surface contamination?

Thanks for the replies. I'm going to sand back and start over. I'm also going to take advantage of this time to epoxy pore fill.
I originally used a powdered filler, which I just couldn't get to stick after about 7-8 applications so I gave up.
I put sanding sealer on top of that so I don't think it's a contamination issue, everything should be compatible.

I'm using black limba/korina back and sides which I know has some pretty deep pores but I wasn't expecting that.
This guitar is my first acoustic and I'm not going for perfection, really just a learning experience and hopefully a decent looking and playable guitar.

yes black limba has notorious pores.
it may pay you to seal fill seal fill seal than finish. One of the few woods that are difficult to fill. I have made a few with this and used pore o paq. had to seal and fill 2 times. On the finish I have a yoke set up that I can turn the body like a roasting pig and used a 10 % retarder 30% thinner on the lacquer and sprayed a heavy coat keeping it turning to avoid runs. Sprayed 2 nd coat in 45 min also heavy and went another 6 coats. Came out nice and flat.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

The only thing I do different is start with lite coats and get heavier only after a good base in place. Seems I get less runs that way.

Thanks John, do you sand back the seal before you fill again? I ran into issues getting white sealer dust in my pores when I had sanded back my sealer after the inadequate job with the powder filler.

Brian,

I had a recent post on this. Titled "every now and again". Take a look. Brian Howard is a goto source for finish skills.

Mike