Why can I see braces through the finish?

[SnowManSnow]

Originally Posted by runamuck

The hazy blush is not from glue - it's from humidity. Either use a retarder or spray when it's less humid. The blush will probably go away but if it doesn't try shooting a straight coat of lacquer thinner on it.

i got that response from someone too. what I've done is put it in a room , a sealed one, directly after spraying. It seems to have fixed the blushing.

[SnowManSnow]

The humidity in there is set at 45


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[mirwa]

A follow up on blushing, this phenomena is caused from high humidity or non ideal temperatures.

The applied paint in general has a milky look to it.

Why ? - When you spray, the lacquer picks up moisture as it leaves the gun and before it hits the guitar, if the temperature is high, then the paint will skin over after landing on the surface, the skinned over paint wont let the water evaporate and in turn create a milky look to the finish.

If it stays milky, then you need to soften the existing coating and the easiest way to do that is to spray some straight thinners onto the surface, this softens the lacquer and the moisture can escape. Sometimes even a heat gun on the surface can release the trapped moisture.

If you do not remove the blush during painting and it drys, then you are likely going to have to sand the lacquer off and start again.

Once you have established there is an issue, you need to address the problem, either apply the right conditions to spray it in or add some retarder to the mix (we use this when spraying in winter)

Steve

[SnowManSnow]

Originally Posted by mirwa

A follow up on blushing, this phenomena is caused from high humidity or non ideal temperatures.

The applied paint in general has a milky look to it.

Why ? - When you spray, the lacquer picks up moisture as it leaves the gun and before it hits the guitar, if the temperature is high, then the paint will skin over after landing on the surface, the skinned over paint wont let the water evaporate and in turn create a milky look to the finish.

If it stays milky, then you need to soften the existing coating and the easiest way to do that is to spray some straight thinners onto the surface, this softens the lacquer and the moisture can escape. Sometimes even a heat gun on the surface can release the trapped moisture.

If you do not remove the blush during painting and it drys, then you are likely going to have to sand the lacquer off and start again.

Once you have established there is an issue, you need to address the problem, either apply the right conditions to spray it in or add some retarder to the mix (we use this when spraying in winter)

Steve

appreciate the explanation.
so its actually picking the moisture up in the air on the way to the surface.
you know... heres the other thing. This happened on the last coat of that can.. there wasn't much nitro left.. i wonder if that being the last bit had something to do with it.
interesting

[Sperry]

Expanding gasses gain heat ...

After spraying nine plus nine coats* of nitro in my kitchen last winter, I swore I'd never ever spray that stuff inside my house again.

* I ruined the finish on the last of the first nine coats and sanded back to wood.

[LouieAtienza]

It could be how you sand too. If you use a bit of pressure when you sand, you can actually make the plates thinner where the braces are because it meets with less resistance, and the area where there are no braces thicker because it gets pushed down by whatever you used to sand. So it leads to the possibility that the wood at the braces end up sanded a bit finer than the areas without, which would lead to less absorption.

If it was your last can and you tried to get as much on, it is also possible that the air/finish ratio in the can was not proper and it flash-dried on the surface, giving you a grainy texture.

[SnowManSnow]

All good thoughts. Thanks guys


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[SnowManSnow]

Originally Posted by Sperry

Expanding gasses gain heat ...



After spraying nine plus nine coats* of nitro in my kitchen last winter, I swore I'd never ever spray that stuff inside my house again.



* I ruined the finish on the last of the first nine coats and sanded back to wood.

There's no way in hell you should spray this in your house ! Ha
Ummm have you been .... sick?


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[LouieAtienza]

Originally Posted by Sperry

Expanding gasses gain heat ...

After spraying nine plus nine coats* of nitro in my kitchen last winter, I swore I'd never ever spray that stuff inside my house again.

* I ruined the finish on the last of the first nine coats and sanded back to wood.

You're lucky no one came in and flipped a switch on you. That's like a bomb waiting to go off!

[Howard Klepper]

Originally Posted by Sperry

Expanding gasses gain heat ...

If pressure is constant--Charles's Law.

But heat is not what causes moisture blush. It's temperature drop from evaporation of the volatiles from the lacquer surface--liquids changing state to gasses take heat (latent heat) away from the surface; and the subsequent expansion of the gasses does not matter to blushing. When the surface cools to the dew point, water vapor condenses on the lacquer surface, and is absorbed into the lacquer. You get it spraying in an environment which has too high a dew point and too rapid evaporation of the solvents and vehicles, which is a warm and humid one. Often it will disappear in the next day or so as the water evaporates from the finish. If the solvents are less volatile (using retarders) and evaporate more slowly, the temperature drop from their evaporation will be less, cooling the surface less and preventing the blush.

The braces add thermal mass, which keeps the back adjacent to them from cooling as rapidly as the rest.