Nitro and Humidity

Airplane

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I know humidity shouldn’t be over ~55% when spraying. Is that for the actual moment of spraying or for the whole procces?

In other words:

Let’s say humidity is 50% for 3 hours around noon. But is a lot higher in the morning and evening. Can i do three coats in one or two hours while the air is dry and then let it sit over night?

Never had to deal with this before because i had access to a proper facility. I don’t have that anymore...
 

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fatdaddypreacher

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as recently as two hours ago i just sprayed some guitars i've been waiting to do for 3 months. short answer to my experience....i've never had a problem if the humidity remained favorably an hour after shooting. I'm in louisiana, and I have a schedule on my local weather app that shows humidity as it is, and also forcasts it on a per hour basis for the next 48 hours. this afternoon, even though it is near 100 degrees, the hum dropped to 40 percent, so i shot. crystal clear, and dry to touch after an hour. I've never had them blush when hum was okay when i shot, but went up over night. seems to be that once it is dry to the touch, hum will no longer affect it, but that's just my limited experience. hope that helps. p.s. i try not to shoot when hum is above 50.
 

Wallied

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It's mostly got to do with the actual moment of spraying, as the moisture slows down the evaporation rate (the more moisture there is in the air, the more of it is trapped in the finish). You can play the balancing game with the humidity, temperature, gun settings and your choice and ratio of thinner. You'll eventually learn the effects these have on your spraying.

Or you could try to always spray in similar environment to eliminate some factors. I wouldn't risk ruining the finish and would instead wait for a drier weather just to be on the safe side if the humidity raises by a lot.
 

ARandall

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Yep, it's the trapping of moisture in the air that was around the guitar and spray stream during application that is the issue. Once the coat has definitively flashed off the chance of blush drops considerably.
 

LtDave32

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You can eliminate the blush instantly. Just give the affected area a quick, dusty shot of retarder.

Behlen's Blush Reducer, in the aerosol can is what I use. -on those rare occasions that high humidity enters my desert environment enough to blush my work.

If you do that, don't touch it for several hours. What retarder does is open up that lacquer "skin" to let the trapped moisture evaporate away. It "retards" the drying time, so the surface is sticky for a bit longer. Not too bad though. Hit it, watch the blush go away, come back in the morning and you'll be fine.
 

fatdaddypreacher

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how long after hitting it with retarder will it be subject to dust or bugs sticking to it?
 

LtDave32

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how long after hitting it with retarder will it be subject to dust or bugs sticking to it?
A fair while, really. It will be tacky for hours. At leasr 4 or so. But it will flow out nice.

Also, it will stay tacky longer in cold weather. When cold, let it alone for two days at least. Check it first before handling.
 

moreles

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Just remember that while blushing, and dripping, and other "wet" problems diminish relatively quickly, you should still remember that overall, deeper "drying" takes longer if the humidity returns, and too-fast buildup of soft layers can be bad in other ways. In my experience, impatience in spraying coats always ends up biting me on the butt, and patience/caution always leads to my best results. Always.
 

Airplane

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Thanks for your input.

I‘ll probably go for at least a 60/40 mix (lacquer /thinner) so that it dries a little bit faster..

Here in switzerland the humidity rarely goes under 45% so 50 is probably not too bad. It raises over 70 at night tho.. All year round i think. Right now i have around 77f at daytime and 50f at night. I guess i‘ll try it. One thing is don’t want i checking while i‘m still in the process or before sanding.. Could happen since i‘m using old fashioned lacquer.

If it develops some milky haze because of humidity, will it go away when i spray over it again the next day? Or is the mess then trapped in between the coats?
 

Freddy G

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Thanks for your input.

I‘ll probably go for at least a 60/40 mix (lacquer /thinner) so that it dries a little bit faster..

Here in switzerland the humidity rarely goes under 45% so 50 is probably not too bad. It raises over 70 at night tho.. All year round i think. Right now i have around 77f at daytime and 50f at night. I guess i‘ll try it. One thing is don’t want i checking while i‘m still in the process or before sanding.. Could happen since i‘m using old fashioned lacquer.

If it develops some milky haze because of humidity, will it go away when i spray over it again the next day? Or is the mess then trapped in between the coats?
Read post #5 again from LtDave32.

He outlined the exact and proper fix for blushing. Mist some retarder on the blush area. It melts the lacquer and keeps it melted long enough for the trapped moisture to escape. Of course you have to do this when the humidity is reasonable.
 

LtDave32

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Thanks for your input.

I‘ll probably go for at least a 60/40 mix (lacquer /thinner) so that it dries a little bit faster..

Here in switzerland the humidity rarely goes under 45% so 50 is probably not too bad. It raises over 70 at night tho.. All year round i think. Right now i have around 77f at daytime and 50f at night. I guess i‘ll try it. One thing is don’t want i checking while i‘m still in the process or before sanding.. Could happen since i‘m using old fashioned lacquer.

If it develops some milky haze because of humidity, will it go away when i spray over it again the next day? Or is the mess then trapped in between the coats?
Actually, you don't want it to dry faster. This develops the skin that traps the moisture.

If you've got a blush situation, it's best to open up that skin with some retarder, then let it dry naturally.

Stew-mac has Behlen's blush remover in aerosol can. It will do the job right. Small investment with good results.

Amazon has it too. Behlen Jet Spray blush eraser. $1199. Same price as Stew-Mac.
 

Airplane

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Actually, you don't want it to dry faster. This develops the skin that traps the moisture.

If you've got a blush situation, it's best to open up that skin with some retarder, then let it dry naturally.

Stew-mac has Behlen's blush remover in aerosol can. It will do the job right. Small investment with good results.

Amazon has it too. Behlen Jet Spray blush eraser. $1199. Same price as Stew-Mac.
Ok i got it. So 50/50 or maybe 40/60 like i usually do.

This blush eraser stuff sounds interesting. I‘ll have a look on that.
 

Airplane

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Read post #5 again from LtDave32.

He outlined the exact and proper fix for blushing. Mist some retarder on the blush area. It melts the lacquer and keeps it melted long enough for the trapped moisture to escape. Of course you have to do this when the humidity is reasonable.
Doesn’t answer my question if just another coat (or even just thinner) helps at all.
 

LtDave32

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Doesn’t answer my question if just another coat (or even just thinner) helps at all.
Go ahead and mist some lacquer thinner on there and see if it works. Chances are, it will merely soften the surface then dry again before the moisture is released.

-because that's what happened when I tried spraying thinner on a blush. It didn't help very much. This is experience talking.

More than one of us has shown what to do in case of blushing caused by moisture. And we've given the reason why it happens.

It's totally up to you to follow that advice. That advice, in the friendliest terms possible, is to put down the thinner can and pop the 12 bucks for some retarder/blush eraser.

-best of luck to you.
 

Airplane

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Go ahead and mist some lacquer thinner on there and see if it works. Chances are, it will merely soften the surface then dry again before the moisture is released.

-because that's what happened when I tried spraying thinner on a blush. It didn't help very much. This is experience talking.

More than one of us has shown what to do in case of blushing caused by moisture. And we've given the reason why it happens.

It's totally up to you to follow that advice. That advice, in the friendliest terms possible, is to put down the thinner can and pop the 12 bucks for some retarder/blush eraser.

-best of luck to you.
Really appreciate the answers. Just wanted to know if thinner works or not. Thanks.
 

pshupe

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Really appreciate the answers. Just wanted to know if thinner works or not. Thanks.
As Dave noted it can work and also just spraying another coat may work as well. It depends how deep the trapped moisture goes. I have had good luck when having blush. The one day was quite humid but the next was not so I just sprayed my next coat and it all went away. Good luck.

Cheers Peter.
 




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