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I am doing the 3 final glossy coats of nitro. I had been letting the other coats cure for 3 weeks. so now when I spray these thin coats I get a "hazy layer on top of the finish looks like cigarette smoke kinda. I can also see the contours of the bracing through the mist. I have heard it can be water in the lines etc but I have never had this before and also have 3 water traps along the lines ( 1 on the compressor, 1 I meter down the hose and 1 under the gun. I am using the right pressure ( as I have used before without getting this mist. )

gonna be spraying the last coat tonight, so I would be happy for some quick replies
the thinning is now about 60%/40% thinner/nitro at this stage.

All the best Lars

I was just spraying a guitar this morning and had the same thing. You need to add some retarder to the nitro. This slows it down enough to let the water evaporate out.

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Lars: How about the R.H. ???
Tom

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That is a lot of thinner Lars. Not sure why you would get blushing with that mix unless it is a really fast thinner. I would suggest less thinner and maybe a slower thinner, or a little retarder.

RH is around 50 now, as I have a window open to let the air get an "In" source for the fan. but the weather is really hot around 30C the basement where I am is a little colder though. around 25 ( we dont use airconditions here as it´s not this how here usually.
Ok I sprayed a new layer just now, with a 50/50 thinner/ laquer. I didn´t get as much blushing but it is still there some. hmm as I sprayed a few weeks ago using the same mix and the same thinner/laquer I did not get this at all !! . so perhaps its the weather.

Lars

Did a last spray for tonight, went by the "step by Step" book, where it is mentioned that "if you want a no buffing needed finish then spray the last coat with 10% laquer and 90% thinner. So I though i would try that, went great all over, no runs and really glossy, BUT I guess the smooky haze is caused by the thinner as this time the top got so smooky looking as it almost looks like frost all over. like taking out an icecream from the fridge or like breathing close on a window. hmmmmm guess i will have to buy some retarder then. and pray it will disapare. and perhaps change the thinner. this one is called cemthinner or something, got it from where the autosprayers gets there stuff from in a 5 liter can.
the "frost" starts coming quite fast about 10 sec after finish spraying.

Lars

On my very first guitar, which was a kit, I had dyed it dark, and sprayed it outside when it was very humid. Got lot's of blushing. I fixed it by taking into the air conditioned part of my shop and sprayed it with straight lacquer thinner, let it dry, then repeat until the blushing disappeared. Make sure you wear a respirator and turn off any kinds of ignition.

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Regards,
Phillip Patton

http://www.pattonblades.com

The bitterness of poor quality lingers long after the sweetness of low price has faded.

https://hoosierbladesmith.wordpress.com

Yes am thinking it might be the weather asI never had this prob... when it was not so hot as it is now. (about security, I have it covered . fireproof fan, light etc. also in a humidity controlled shop. (semi controlled haha)

Lars

Lars, I live in a "blush prone" area and have to be extremely conscious of conditions that promote it. You describe drawing warm, moderately humid air from outdoors, but you're spraying in a cooler, more humid basement. The lacquer mixture cools when it is atomised by the spray gun under pressure. When that temperature drops below the "dew point", water condenses on the spray droplets and you get blush. Water in airlines can be a problem, but that is much less likely if you're using traps and draining the compressor.

Using retarders or ultra-slow thinners can discourage formation, but might not themselves be enough to drive it out. Note that too much ultra-slow thinner or retarders can interfere with curing, and that's a problem you don't need.

You need a much lower dew point (moderately high temperature and lower humidity) and/or warmer mixture (known as "hot potting"), then a mixture at normal proportions of thinner should be sufficient to cause the blush to disappear. Your product manufacturer should have detailed spec sheets online that will give guidance on compatible thinners, their speed, and maximum proportions -- worth being familiar with these.

Having had to deal with this, I now monitor atmospheric conditions inside and outside, and don't spray unless the dew point is at least 6C° below ambient dry-bulb temperature. Problem hasn't recurred.

Good luck, but be assured that when you next spray under good, dry conditions, the blush should disappear.

Tim

Thanks Tim for a great explanation !!!! . I really appreciate it ! . I will go talk to the people I bought the laquer and thinner from tomorrow and see what they say .

Lars

Yep, I've had to use retarder on two of mine because of humidity (I spray outside also). If the blush isn't too bad, a trick you can do it to use a hair dryer, on high heat setting, but low fan speed, and heat up the blushed area slightly...and the blush usually disappears.

Bill

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I have found that warming my pot in warm water for a few minutes prior to spraying helps with this too. This goes for (for instance Stew-Mac) spray lacquer in a can too. Of course 99% of the time...humidity isn't the real problem here in Colorado...only temp variations between lacquer/guitar itself and air temp. All 3 can cause finish disparities. I always attempt to have the spray a bit warmer than the room temp and make sure the wood surface acclimates to the spray room or outside temp before spraying.

For what its worth.
KB

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