Paint Fogging, Strange Reaction

[StevenGuthmiller]

I have a question for all of you chemical engineers out there.

I know that there have been many topics & discussions regarding automotive spray lacquers & the affects of humidity on the paint, but I've noticed an unusual phenomena with many of my paint jobs that I've used Duplicolor rattle cans on that makes me wonder about the "humidity" argument.

First of all, I'm painting in my basement where it is air conditioned to a cool & comfortable 74 degrees.

I almost always have "fogging" in the paint when I use the Dupliclor paint whether it's spring, summer, winter or fall & it's not a big deal as It's never a problem after clear coats & polishing, but I've noticed a peculiarity that has me scratching my head a little.

I sometimes mount my bodies on an old paint can for spraying paint & I've noticed no fogging in any areas where the back side of the plastic has anything mounted to it.

The roof of my '61 Buick has a perfect round area in the center of the roof that is un-fogged where the can is taped to the underside.

Even the sides of the body where the can is situated are not fogged where the can is close, but not touching.

The remainder of the body is fogged.

Maybe something to do with the temperature of the can, you might ask?

Possibly. But that would not explain the same phenomena on the hood.

The hood was mounted for painting on a tooth pick with a piece of tape at the top & the same thing is evident in the center of the hood where the piece of tape is attached to the backside.

I would think there would be little temperature difference between the plastic & a tooth pick & small piece of masking tape.

What's the answer?

I'm wondering if a guy could eliminate the fogging issue by masking off the backside of the body before painting.

Hmmm.

 

Steve

[Art Anderson]

I have a question for all of you chemical engineers out there.

I know that there have been many topics & discussions regarding automotive spray lacquers & the affects of humidity on the paint, but I've noticed an unusual phenomena with many of my paint jobs that I've used Duplicolor rattle cans on that makes me wonder about the "humidity" argument.

First of all, I'm painting in my basement where it is air conditioned to a cool & comfortable 74 degrees.

I almost always have "fogging" in the paint when I use the Dupliclor paint whether it's spring, summer, winter or fall & it's not a big deal as It's never a problem after clear coats & polishing, but I've noticed a peculiarity that has me scratching my head a little.

I sometimes mount my bodies on an old paint can for spraying paint & I've noticed no fogging in any areas where the back side of the plastic has anything mounted to it.

The roof of my '61 Buick has a perfect round area in the center of the roof that is un-fogged where the can is taped to the underside.

Even the sides of the body where the can is situated are not fogged where the can is close, but not touching.

The remainder of the body is fogged.

Maybe something to do with the temperature of the can, you might ask?

Possibly. But that would not explain the same phenomena on the hood.

The hood was mounted for painting on a tooth pick with a piece of tape at the top & the same thing is evident in the center of the hood where the piece of tape is attached to the backside.

I would think there would be little temperature difference between the plastic & a tooth pick & small piece of masking tape.

What's the answer?

I'm wondering if a guy could eliminate the fogging issue by masking off the backside of the body before painting.

Hmmm.

 

Steve

Steve, you mention that you work in the basement of your house:  Even though your basement sounds as though it's part of central air conditioning, I'd be willing to bet that it's still more humid down there than upstairs, given that you live in MN, where ground temperatures stay pretty cool even in the summer.  "Fogging" or hazing of lacquers or lacquer-based paints happens when moisture condenses on the little droplets of paint coming out of a rattle can as well as on wet-paint surface of a model (or any other object being so-sprayed, in my experience) for one simple reason: When you release pressure on an aerosol can, as the compressed propellant escapes, it drops dramatically in temperature (which is why the cautionary statement on those cans of compressed gas people use to clean dust off and out of puter keyboards--warning about possibly freezing skin if you spray directly on it).  This in turn, chills down the minute droplets of lacquer coming out of that nozzle, enough to cause water vapor to condense on them.  It's not a chemical reaction--rather it has a lot to do with the laws of physics.

Except in an extremely humid environment, I've almost NEVER had "hazing" (that almost pearlescent looking surface) when airbrushing lacquers, regardless of humidity, but I do know that my nephew and brother, who are partners in the cabinet-making and antique furniture restoration have been known to have problems in certain highly humid weather conditions.   A solution may very well be as close as your nearest appliance store:  A dehumifier--which will dry out the air in an enclosed room fairly quickly.  I know they aren't cheap, but if you consider that it'd be a one-time buy, that you can use for many years, the price per year, not to mention the reduction in the costs of spray painting model cars should drop dramatically (and your model building satisfaction increase in the bargain!).  Of course, in the dead of winter, unless you have a humidifier to lessen the extremely dry air in bitter outdoor cold, you should not see this problem, as the combination of heating along with the already greatly lower relative humidity outdoors on a 0-degree evening generally dries out the air inside a house dramatically.

 

Art

[StevenGuthmiller]

Steve, you mention that you work in the basement of your house:  Even though your basement sounds as though it's part of central air conditioning, I'd be willing to bet that it's still more humid down there than upstairs, given that you live in MN, where ground temperatures stay pretty cool even in the summer.  "Fogging" or hazing of lacquers or lacquer-based paints happens when moisture condenses on the little droplets of paint coming out of a rattle can as well as on wet-paint surface of a model (or any other object being so-sprayed, in my experience) for one simple reason: When you release pressure on an aerosol can, as the compressed propellant escapes, it drops dramatically in temperature (which is why the cautionary statement on those cans of compressed gas people use to clean dust off and out of puter keyboards--warning about possibly freezing skin if you spray directly on it).  This in turn, chills down the minute droplets of lacquer coming out of that nozzle, enough to cause water vapor to condense on them.  It's not a chemical reaction--rather it has a lot to do with the laws of physics.

Except in an extremely humid environment, I've almost NEVER had "hazing" (that almost pearlescent looking surface) when airbrushing lacquers, regardless of humidity, but I do know that my nephew and brother, who are partners in the cabinet-making and antique furniture restoration have been known to have problems in certain highly humid weather conditions.   A solution may very well be as close as your nearest appliance store:  A dehumifier--which will dry out the air in an enclosed room fairly quickly.  I know they aren't cheap, but if you consider that it'd be a one-time buy, that you can use for many years, the price per year, not to mention the reduction in the costs of spray painting model cars should drop dramatically (and your model building satisfaction increase in the bargain!).  Of course, in the dead of winter, unless you have a humidifier to lessen the extremely dry air in bitter outdoor cold, you should not see this problem, as the combination of heating along with the already greatly lower relative humidity outdoors on a 0-degree evening generally dries out the air inside a house dramatically.

 

Art

That's the problem Art.

The situation does not improve even in the dead of winter.

My basement is mostly finished, & for that matter, is only a "half" basement. (Only about 4 feet underground)

I do realize that the humidity may be higher in the basement, but in the winter time, the air is so dry here that I get a shock every time I touch a light switch, even in my basement. Yet the fogging persists.

As I said, it's not really a problem, I am just wondering why any part of the body that is "backed" by something does not fog.

I only have fogging issues with Duplicolor rattle cans, & only colors for that matter. The clear does not fog.

I also never have this problem with airbrushing lacquers.

 

Steve

 

[Ace-Garageguy]

This sounds like it ought to be worth at least a couple hundred grand ($$$) government study.

Though Art explained the mechanics of fogging due to humidity, your question as to why the areas of your model in contact with something didn't fog went largely unanswered.

My best guess is that the support of the model or part forms enough (not much, obviously) of a heat-sink (heat source in this case) to ever-so-slightly stabilize the temperature of the part it's touching or near to, keeping the part in question from momentarily flashing below the 'dew-point' that causes micro-condensation on the surface of the model or part, and subsequent hazing.

Having always polishes off the surface of lacquers, and is rarely even deep enough to affect the appearance of metallic particles in paint when it's polished carefully.

As you've obviously already noticed, clear-coating kills the hazing too, though the clear itself may haze, needing a polish to remove it.

The first time I encountered lacquer fogging was very early in my painting career. I was painting a real Alfa Romeo Duetto outside, under a parachute (for my booth), and just as I was shooting the last coat, it started to rain. The humidity skyrocketed, terrible fogging, and I thought I'd have to do the entire job over. Called it quits for the evening, came out in the morning and noticed, much as you have, that there were certain areas of the surface hardly hazed at all. On a whim, rubbed my finger over one of the worst-fogged areas. To my delight, it got somewhat better. Color-sanding and compounding made her beautiful again.

EDIT: The fact you don't have the problem airbrushing is a key indicator. Most likely, the temperature drop of the compressed gas propellant in the spray-cans is more than the temp drop you're getting from airbrushing.

I usually get minor blushing with Duplicolor paints, but since I know it will go away, I just don't worry about it.

 

Edited August 15, 2015 by Ace-Garageguy

[Snake45]

Steve, I've had exactly the same thing happen with the same paint. Got a '66 Chevelle in the paint shop now with a case of that. I've noticed that the fogging rubs out very easily though--it seems to be right on top. Hope that's the case with this one.

[StevenGuthmiller]

This sounds like it ought to be worth at least a couple hundred grand ($$$) government study.

Though Art explained the mechanics of fogging due to humidity, your question as to why the areas of your model in contact with something didn't fog went largely unanswered.

My best guess is that the support of the model or part forms enough (not much, obviously) of a heat-sink (heat source in this case) to ever-so-slightly stabilize the temperature of the part it's touching or near to, keeping the part in question from momentarily flashing below the 'dew-point' that causes micro-condensation on the surface of the model or part, and subsequent hazing.

Having always polishes off the surface of lacquers, and is rarely even deep enough to affect the appearance of metallic particles in paint when it's polished carefully.

As you've obviously already noticed, clear-coating kills the hazing too, though the clear itself may haze, needing a polish to remove it.

The first time I encountered lacquer fogging was very early in my painting career. I was painting a real Alfa Romeo Duetto outside, under a parachute (for my booth), and just as I was shooting the last coat, it started to rain. The humidity skyrocketed, terrible fogging, and I thought I'd have to do the entire job over. Called it quits for the evening, came out in the morning and noticed, much as you have, that there were certain areas of the surface hardly hazed at all. On a whim, rubbed my finger over one of the worst-fogged areas. To my delight, it got somewhat better. Color-sanding and compounding made her beautiful again.

EDIT: The fact you don't have the problem airbrushing is a key indicator. Most likely, the temperature drop of the compressed gas propellant in the spray-cans is more than the temp drop you're getting from airbrushing.

I usually get minor blushing with Duplicolor paints, but since I know it will go away, I just don't worry about it.

 

Sounds like as good an explanation as any bill.

As you say, I don't worry about it. It's not really a problem in the long run. It was just interesting to me that that perfect circle of clear, un-fogged paint appears on the roof, & I had to question why.

I guess it's one of those things that I'll never have a satisfactory answer for, but it really seemed to me that humidity would have little to do with it.

I highly doubt that the area backed by the spray can was some how lower in humidity than the rest of the body.

Luckily, I only use non-metallic colors out of a spray can on occasion, like white, black & red, so this issue only arises on those occasions.

Just seems like an interesting dilemma that I thought others may have experienced.

I'm still open to that elusive definitive answer guys.

Let me have it!

 

Steve

[StevenGuthmiller]

Steve, I've had exactly the same thing happen with the same paint. Got a '66 Chevelle in the paint shop now with a case of that. I've noticed that the fogging rubs out very easily though--it seems to be right on top. Hope that's the case with this one.

Yes, I'm sure it is Snake.

I've had this happen with most every build I've painted with Duplicolor.

It's never been a major problem.

 

Steve

[Tom Geiger]

As you describe your conditions, could the hazing be from the temperature / humidity of the body?  Maybe heat up your paint can,  AND warm up the body in a dehydrator prior to painting?    Your description sounds like my basement... cool in summer and if I touch anything there, it's cool to the touch. 

I'm thinking about that because with 1:1 autos, I once got a hazed and rough paint job in the winter ... one of the techs there told me that the reason why was that they pulled the car into the shop from outside and shot the paint without having it warm up to shop temperature. 

Edited August 15, 2015 by Tom Geiger

[Ace-Garageguy]

Only way you're going to get a definitive answer is from rigorous scientific testing. Repeatable. Recorded results. 

Anything else is just opinion, guesswork, repetition or anecdotal.