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ERIK88

identifying the problem / paint question

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so i painted my  Porsche model kit in 70s temp, 67 % humidity I sprayed krylon sunfire yellow warmed in the dehumidifier, sprayed  thin coats in the beginning about 4x each time putting the car in the dehumidifier and then I did a wet coat. I must admit i think i sprayed to much on my final wet coat as i was looking for a gloss look all around. Should I be looking for a gloss all around the body? or should I leave some parts unglossed? I think that  the gloss goes away anyway once the paint dries. Should i expect a gloss at all? or should I just fully cover the model car, and obtain the shine from clearcoat , buff and wax? This is my 4th model in years. I wanna get this right, painting the body always gets me. I dont get it. The paint came out hazy , cloudy as a result, and it also had multiple bubbles or dots around the body all around.

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the model car gets place in the dehumidifier right away fyi. But i saw the hazing beforehand, the bubbling didnt occur until after. Was this going to occur anyway? did the dehumidifier just speed up the process? I would imagine it did since it intensifies taking out the moisture , and drying the paint .

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Eric, did you use an enamel paint, or lacquer? I've never used a dehydrator and seem to get along just fine without it. It's not like I'm gonna build a model in one day, even though I've know guys to do this.

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the model car gets place in the dehumidifier right away fyi. But i saw the hazing beforehand, the bubbling didnt occur until after. Was this going to occur anyway? did the dehumidifier just speed up the process? I would imagine it did since it intensifies taking out the moisture , and drying the paint .

Is there any way you can check the temp inside the dehumidifier? The reason for this is to see if it ever goes above 105 degrees, which, according to what I've read, is the high-end for a plastic model... And I know for a fact that some paints (particularly automotive paints) were not made to be heat-dried - I have had some projects where the outer layer seems dry, but it's so soft, it still shows fingerprints. In regard to "hazing", that could be a temporary effect from getting too much paint in that area. I've had that happen, and it has always cleared up after a while. Just don't spray any more if you see it. Let it dry, instead. You may have some runs or sags at that area that you will want to sand out before painting again. "Bubbling" sounds like "fisheyes", and this again can happen when too much material is applied.

Edited by fseva

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so i painted my  Porsche model kit in 70s temp, 67 % humidity I sprayed krylon sunfire yellow warmed in the dehumidifier, sprayed  thin coats in the beginning about 4x each time putting the car in the dehumidifier and then I did a wet coat. I must admit i think i sprayed to much on my final wet coat as i was looking for a gloss look all around. Should I be looking for a gloss all around the body? or should I leave some parts unglossed? I think that  the gloss goes away anyway once the paint dries. Should i expect a gloss at all? or should I just fully cover the model car, and obtain the shine from clearcoat , buff and wax? This is my 4th model in years. I wanna get this right, painting the body always gets me. I dont get it. The paint came out hazy , cloudy as a result, and it also had multiple bubbles or dots around the body all around.

Did you mean to say Dehydrator? As in a food dehydrator?

Can I ask how the body was prepped before spraying? Sanded? Washed with hot water and TSP?

Did you use Gloss or Satin paint? If it is Gloss it should come out shiney with no need to clear for the shine.

Answer my questions and we can better help you.

Mark

Edited by astroracer

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A photo would speed help along also

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"Air" bubbles in spray paint is a problem as old as rattle cans themselves, particularly enamels (I discovered this problem back in 1959 with the very first paintjobs I did with the then-newly-released Pactra 'Namel "Soft Spray" paint for plastic models.  This problem is caused by humidity--it can cause enamels to "skin over" very quickly which I've found is the primary cause of "hazing" with both rattle can enamels and lacquers. "Hazing" itself, is curable--it polishes right out.

Those nasty little air bubbles are another matter entirely:  When the paint (particularly enamels) "skins" over too rapidly, the paint has still not out-gassed its propellant gas (spray can propellant does get dissolved into the paint, in the can, under the rather high PSI needed in order to propel the paint out in a fine spray).  If the paint surface dries too quickly, that gas (generally propane nowadays, BTW) has no place to go, and as with bubbles in a glass of soda, they tend to gather together in ever larger bubbles.

There really is no solution to this problem other than stripping the paint, and starting all over.  Living in the Great Lakes region, we all face this at some time or another--the only thing to do is wait either for the humidity to drop, or paint in the heat of day when the relative humidity is lower than it would be say, at night.  Another solution is to paint indoors, with airconditioning (will take some work to keep the rest of the family happy though!), or get a dehumidifier, which will dry out the air inside the house (or at least in a room) enough to prevent this from happening.

Also, I'd wait for the paint to begin to dry, at least to the "tacky" stage, before putting it in the dehydrator (which device I use religiously BTW), so the propellant has as much time as possible to out-gas before the surface of the paint traps it.

 

Art (who's been spray painting model car body shells (both aerosol can AND airbrush) for now a good 56 years.

 

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Eric, did you use an enamel paint, or lacquer? I've never used a dehydrator and seem to get along just fine without it. It's not like I'm gonna build a model in one day, even though I've know guys to do this.

I actually used krylon lacquer spraycan . I know how you feel, but idk I can't go without using that thing ! It just seems fascinating how it can instantly dry paint for ya 

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Did you mean to say Dehydrator? As in a food dehydrator?

Can I ask how the body was prepped before spraying? Sanded? Washed with hot water and TSP?

Did you use Gloss or Satin paint? If it is Gloss it should come out shiney with no need to clear for the shine.

Answer my questions and we can better help you.

Mark

thanks a lot for your response mark , the body was washed with soap firsthand, dried and primered in krylon grey primer, put in the dehydrator,  then two days later sanded with 600 grit 800 1500 grit, then washed with soap. Once dry, I primed with duplicolor white primer. Thin coats, about 6 then set to dry once again in the dehydrator. The body was taken out of the dehydrator then sanded smooth same grits  of sandpaper, smoothed out washed in dishwasher soap. I then waited for the body to dry, and warmed up my krylon sun fire yellow spraycan for about 10 minutes in the dehydrator. The body was then sprayed with this spray can with about 4 thin coats, 5-10 min intervals on each coat depending on how heavy I went on paint. I finally did one medium coat , I waited for another 5 min (body placed in the dehydrator within each coat after) . I finally did a heavy coat, as I sprayed I wasn't achieving a gloss, only in some areas . This is part of what cause the overspray. I wanted to get somewhat of a gloss. I finally stopped, and realize I went over, but not to the point where paint is running or sagging, it simply has a deep look to the point it took out some panel detailing. About 3 min after I saw clouding  in the paint. It remained hazy, however as soon as I placed in the dehydrator multiple little tiny dots (not circular fish eyes ) where all over the paint . 

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A photo would speed help along also

I got so frustrated I didn't take a pic . Lol 

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thanks a lot for your response mark , the body was washed with soap firsthand, dried and primered in krylon grey primer, put in the dehydrator,  then two days later sanded with 600 grit 800 1500 grit, then washed with soap. Once dry, I primed with duplicolor white primer. Thin coats, about 6 then set to dry once again in the dehydrator. The body was taken out of the dehydrator then sanded smooth same grits  of sandpaper, smoothed out washed in dishwasher soap. I then waited for the body to dry, and warmed up my krylon sun fire yellow spraycan for about 10 minutes in the dehydrator. The body was then sprayed with this spray can with about 4 thin coats, 5-10 min intervals on each coat depending on how heavy I went on paint. I finally did one medium coat , I waited for another 5 min (body placed in the dehydrator within each coat after) . I finally did a heavy coat, as I sprayed I wasn't achieving a gloss, only in some areas . This is part of what cause the overspray. I wanted to get somewhat of a gloss. I finally stopped, and realize I went over, but not to the point where paint is running or sagging, it simply has a deep look to the point it took out some panel detailing. About 3 min after I saw clouding  in the paint. It remained hazy, however as soon as I placed in the dehydrator multiple little tiny dots (not circular fish eyes ) where all over the paint . 

I really appreciate the help, I love this hobby but can't seem to spray car body's good . This is my second model it's happened on, I eventually got a decent spray on the first model it happened on but I can make out what causes this . It's frustrating , it seems like I follow every rule in the book. I spray about 3-5 inches away too

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"Air" bubbles in spray paint is a problem as old as rattle cans themselves, particularly enamels (I discovered this problem back in 1959 with the very first paintjobs I did with the then-newly-released Pactra 'Namel "Soft Spray" paint for plastic models.  This problem is caused by humidity--it can cause enamels to "skin over" very quickly which I've found is the primary cause of "hazing" with both rattle can enamels and lacquers. "Hazing" itself, is curable--it polishes right out.

Those nasty little air bubbles are another matter entirely:  When the paint (particularly enamels) "skins" over too rapidly, the paint has still not out-gassed its propellant gas (spray can propellant does get dissolved into the paint, in the can, under the rather high PSI needed in order to propel the paint out in a fine spray).  If the paint surface dries too quickly, that gas (generally propane nowadays, BTW) has no place to go, and as with bubbles in a glass of soda, they tend to gather together in ever larger bubbles.

There really is no solution to this problem other than stripping the paint, and starting all over.  Living in the Great Lakes region, we all face this at some time or another--the only thing to do is wait either for the humidity to drop, or paint in the heat of day when the relative humidity is lower than it would be say, at night.  Another solution is to paint indoors, with airconditioning (will take some work to keep the rest of the family happy though!), or get a dehumidifier, which will dry out the air inside the house (or at least in a room) enough to prevent this from happening.

Also, I'd wait for the paint to begin to dry, at least to the "tacky" stage, before putting it in the dehydrator (which device I use religiously BTW), so the propellant has as much time as possible to out-gas before the surface of the paint traps it.

 

Art (who's been spray painting model car body shells (both aerosol can AND airbrush) for now a good 56 years.

this is some really good info! Thanks . So do you think that every time I shoot a layer of paint I'm causing for the paint to dry to quickly? I think that's were my problem might be. Because every time I shoot a layer of paint I place eighth back in the dehydrator along with can and wait 5-10 min and go on model cars mag while I wait ;) haha .

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I respectfully suggest you practice and develop your spray techniques BEFORE you paint models that you want to look good.

Small plastic pop bottles make good test subjects. Do all your prep and paint steps the same as you do on a model.

Find out what works, reliably, every time, and then stick to a known procedure with the same materials.

Constant experimenting, mixing materials from various companies (without thorough testing first) and trying to rush-dry your paint are all disasters waiting to happen.

It's a LOT more fun to do this stuff when you KNOW your paint will come out right.

Edited by Ace-Garageguy

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It's a LOT more fun to do this stuff when you KNOW your paint will come out right.

Hala-f-in yoo-ya!

I can tell you that from my experiance, paint issues make it a miserable expeirence.

Pitning is tough.  But once a workflow is developed, then it seems to fall into place.

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I respectfully suggest you practice and develop your spray techniques BEFORE you paint models that you want to look good.

Small plastic pop bottles make good test subjects. Do all your prep and paint steps the same as you do on a model.

Find out what works, reliably, every time, and then stick to a known procedure with the same materials.

Constant experimenting, mixing materials from various companies (without thorough testing first) and trying to rush-dry your paint are all disasters waiting to happen.

It's a LOT more fun to do this stuff when you KNOW your paint will come out right.

thanks for the advice, I honestly try do do things as procedurally right as possible. I hated the fact that it seems to be a hit or miss deal most of the time. For example, I've experimented under higher or lower  temps diff acceptable humidity levels  on my Mpc svo mustang which came out right in like the third try lol. That kit had krypton primer and krylon gloss black , no other brand paints used. It still developed those tiny dots everywhere. I try to follow everything by the book, I gotta be doing somethi g wrong by speed drying. I should try not to rush so much.  Those dang little dots or pimples whatever you wanna call them get me !

Edited by ERIK88

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i

i came d across a good reference online , and this is how the model looked in yellow paint.pimples, but not so extreme 

 

image.jpg

Edited by ERIK88

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"And I know for a fact that some paints (particularly automotive paints) were not made to be heat-dried"

This is news to me. Can you give a source for this? Body shop suppliers sell and promote many kinds of driers( Heat lamps etc) for speeding the curing of paint work. Time is money in body shops, Anyone here work in body repair daily have any comments on this? 

Thanks

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"And I know for a fact that some paints (particularly automotive paints) were not made to be heat-dried"

This is news to me. Can you give a source for this? Body shop suppliers sell and promote many kinds of driers( Heat lamps etc) for speeding the curing of paint work. Time is money in body shops, Anyone here work in body repair daily have any comments on this? 

I've been in and out of the bodyshop business for over 40 years...mostly high-end collision and restoration work where quality was the most important goal...and your assertion that "time is money" in the biz, and that materials are developed specifically to speed the process is right on.

HOWEVER, only a fool in the biz fails to read and go by the specific TDS for any given material (technical data sheet). Expecting one to behave like another you may be used to is just plain stupid, and certain to kill your profits.

Specific materials require specific handling and techniques, and making generalizations isn't smart or helpful.

NOTE: The OP's reference photo looks rather like "solvent popping", where solvents (the thinner in paint, NOT the propellant) is trapped under a too-quickly-dried surface from...surprise...forcing heat on paint before it's sufficiently gassed out, or from piling on successive coats before the underlying coats are sufficiently dry. As the surface is hard and impermeable to solvent vapor, the solvent still tries to get out. It forms little blisters or bubbles during its escape.

It's a model. No angry client or insurance company is bugging you to get it done faster. But if you screw it up, you'll still do it over again for free. 

Don't rush it.

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I really appreciate the help, I love this hobby but can't seem to spray car body's good . This is my second model it's happened on, I eventually got a decent spray on the first model it happened on but I can make out what causes this . It's frustrating , it seems like I follow every rule in the book. I spray about 3-5 inches away too

the body was washed with soap firsthand, dried and primered in krylon grey primer, put in the dehydrator,  then two days later sanded with 600 grit 800 1500 grit, then washed with soap. Once dry, I primed with duplicolor white primer. Thin coats, about 6 then set to dry once again in the dehydrator.

I was just wondering, Erik, why you expend so much energy in the primer phase? From what I have read here, you have 7 coats of primer on this model! You would normally have that many primers when you found areas that needed more sanding, and you were using the primer to point out those areas. If you've prepared your model before priming by removing the mold lines, etc., and you give it one coat of primer... if you don't see any small scratches, or any unlevel areas... it's ready for finish paint!

Btw, are you sure 3-5" is the "recommended" distance from your object? Usually, these big cans recommend getting further back than that... Check the can and let us know... This could be why you're getting too much paint on the model at one time...

Edited by fseva

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Eric, did you use an enamel paint, or lacquer? I've never used a dehydrator and seem to get along just fine without it. It's not like I'm gonna build a model in one day, even though I've know guys to do this.

hello, it was actually a lacquer spray an 

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In addition to the things already posted, I would say 3-5 inches is way too close for rattle cans.

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I was just wondering, Erik, why you expend so much energy in the primer phase? From what I have read here, you have 7 coats of primer on this model! You would normally have that many primers when you found areas that needed more sanding, and you were using the primer to point out those areas. If you've prepared your model before priming by removing the mold lines, etc., and you give it one coat of primer... if you don't see any small scratches, or any unlevel areas... it's ready for finish paint!

Btw, are you sure 3-5" is the "recommended" distance from your object? Usually, these big cans recommend getting further back than that... Check the can and let us know... This could be why you're getting too much paint on the model at one time...

I agree with you guys, I think I'm putting on too much primer and the spraying distance should be 10-12 inches, :) thanks for the tips and support 

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