Nitro and Humidity

greens

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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...
I'd say that is a little conservative. I've never had a problem under 65% or so
 

greens

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That’s music to my ears!
Well, I don't want to lead you astray because I'm far from a pro. But I've done a handful of guitars. Would love to hear what other people think about it.
 

pshupe

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I've sprayed in 60 - 65% and had blush but the next day was not so humid and I sprayed another coat and it melted in and the air escaped, so it seemed to work out OK. I would have some retarder on hand if you were spraying in that humidity and try not to, if you can help it.

Cheers Peter.
 

emoney

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I didn't know there was any such thing as humidity under 90% actually. Down here in Florida, if we had to wait until it was in the 50% area we would never be able to spray.

Thin coats......thin. Skinny. Barely there.
 

vintageguitarz

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OK, I'm going to give you the perspective of a manufacturer. I worked for Fender for 27 Years from 1972 to 1999, now a Luthier who repairs, restores vintage instruments and builds maybe a dozen customs per year,

"Shooting" the body and neck is the most important phase in the physical construction of a fine instrument. If you're building just a "player", yeah who cares. If you are building an instrument you intend to be proud of, show off and enjoy looking at for as long as you play it, you painstakingly control the environment where you do your work. In a shop, a custom mfg facility and a factory you control the temperature and the humidity 24/7. If you want the finish to spider crack or worse in 4 to 10 years, then who cares. Shooting a guitar is not something you DON'T do in your yard or a dirty garage. 45 to 55% (worst case limit) Humidity while you shoot nitrocellulose and while it cures. Even using Poly and other finishes require a controlled CLEAN environment. Take pride in your work, do it right.

Fender Custom Shop - Corona.jpg
 

pshupe

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OK, I'm going to give you the perspective of a manufacturer. I worked for Fender for 27 Years from 1972 to 1999, now a Luthier who repairs, restores vintage instruments and builds maybe a dozen customs per year,

"Shooting" the body and neck is the most important phase in the physical construction of a fine instrument. If you're building just a "player", yeah who cares. If you are building an instrument you intend to be proud of, show off and enjoy looking at for as long as you play it, you painstakingly control the environment where you do your work. In a shop, a custom mfg facility and a factory you control the temperature and the humidity 24/7. If you want the finish to spider crack or worse in 4 to 10 years, then who cares. Shooting a guitar is not something you DON'T do in your yard or a dirty garage. 45 to 55% (worst case limit) Humidity while you shoot nitrocellulose and while it cures. Even using Poly and other finishes require a controlled CLEAN environment. Take pride in your work, do it right.
I would have to respectfully disagree that you need a controlled CLEAN environment. I do keep my shop climate controlled 24/7 but it is quite dusty and I do not have an air cleaner filter system. Nitro is very forgiving. I have only sprayed a handful of guitars but I have yet to get any contamination in the finish. Also I know more than a couple of people that spray at least 12 and as many as 30 guitars a year in the same manner without issue.

Before I spray I spend a bit of time blowing off the surfaces and vacuuming up as much as I can but it does not take me very long. The nitro I use dries almost instantly, or at least to the point where it wouldn't have something stick to it. I also do not put down any drop clothes. By the time the overspray hits a surface beyond the guitar it is pretty much dry and is just a dust / powder. I spray towards my table saw and work bench and have no issues.

Regards Peter.
 

Airplane

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I‘m done with the spraying Bd it worked pretty good. I bought a hygrometer just to be sure and the humidity turned out to be pretty low around noon. 40 to 50 max for a couple of hours. I left it outside for tonight with a cloth hanging loosely over it to catch some moisture in the early morning hours. A trick i learned for tanning skins in my taxidermy apprenticeship.

Dust and stuff was absolutely no problem at all, even tho i did it on my balcony.

Thanks for your help.

Have a look at my makeover thread if you’re interested how the guitar turns out:
 

lpfan1980

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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...
Someone stick their lester in a sauna what will happen? :p
 

LtDave32

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I would have to respectfully disagree that you need a controlled CLEAN environment. I do keep my shop climate controlled 24/7 but it is quite dusty and I do not have an air cleaner filter system. Nitro is very forgiving. I have only sprayed a handful of guitars but I have yet to get any contamination in the finish. Also I know more than a couple of people that spray at least 12 and as many as 30 guitars a year in the same manner without issue.

Before I spray I spend a bit of time blowing off the surfaces and vacuuming up as much as I can but it does not take me very long. The nitro I use dries almost instantly, or at least to the point where it wouldn't have something stick to it. I also do not put down any drop clothes. By the time the overspray hits a surface beyond the guitar it is pretty much dry and is just a dust / powder. I spray towards my table saw and work bench and have no issues.

Regards Peter.
I never have a problem spraying in open shop.
 




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