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Whitish/milky result when airbrushing dullcote

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Whitish/milky result when airbrushing dullcote
Posted by CHARLES A TREVEY on Wednesday, January 10, 2018 4:54 PM

Hi. I have had some unpredictable results when airbrushing dullcote lacquer coatings and was interested to know if anyone else has had this problem and found a cure. I mix this product one to one with automotive lacquer thinner. It goes on wet and smooth but dries to a milky whitish finish. My air pressure is 30 psi which works well for all of my other paint coatings. I wonder if some other type of non lacquer based clear coat would be better to use. Thanks for your comments. 

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Posted by dknelson on Thursday, January 11, 2018 10:00 AM

It seems odd that I do NOT have this problem with spraying Dullcote "pure" out of a rattlecan.  Is your DullCote very old?  I ask that because some years ago I believe they changed the formula for the stuff.  If I recall right the "old" DullCote had talc suspended in the clear medium.  Sometimes you would get milky or unpredictable finishes from that stuff.

Dave Nelson

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Posted by RR_Mel on Thursday, January 11, 2018 10:35 AM

I used Testors Dullcoat in the spray can for years and never had a problem.  About four years ago I started using True Color Paints for my locomotives and touch up, it works so good I thought I would try their clear flat in my airbrush.  It has worked out as good or better than Testors.  I can adjust the spray for small areas much better than a rattle can.  Most of the True Color Paints are gloss and need a clear flat sealer.
 
I use Acetone to thin the True Color Paints and cleanup my airbrush and brushes.   
 
 
 
Mel
 
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Posted by 7j43k on Thursday, January 11, 2018 10:42 AM

I sorta slightly recall that it's been noted that high humidity while spraying clears can cause this problem.  I repeat:  sorta slightly recall.

The pressure is higher than I use, though I don't see why that would do it.  I spray at around a start of 15 psi.

Regarding the talc comment, above.  I think it's "always" in clear flat.  The talc, or whatever other substance is used, creates the flatness.  I've been known to let the clear-flat settle in the bottle, and pour off some of the clear.  This makes the coating more flat.

 

Ed

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Posted by j. c. on Thursday, January 11, 2018 11:18 AM

are you painting over acrilics , enamal  or other laqure ?

how long are you waiting to clear coat ?

what thinner are you using  ? fast / medium/ slow

air pressure sounds a bit high , try lowering pressure.

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Posted by doctorwayne on Thursday, January 11, 2018 11:22 AM

Welcome to the MR Forums, Charles!

I've never had that problem airbrushing Dullcote, and have always used lacquer thinner, although perhaps 1/3 thinner to 2/3 Dullcote, and a little lower pressure - depends on the results I want for any particular project.
I've read that alcohol can turn already-applied Dullcote white, but that effect can be negated by another overspray of Dullcote - that doesn't appear to be the situation here, though.

What type of paint did you use?  Some paints dry rather quickly, but take longer to fully cure.  It used to be said that the "sniff test" will tell you if the paint is fully hardened, but many of today's acrylics have very low odour, even from an open bottle. 

I usually wait several days after painting to apply any clear coats, especially if I'm using lacquer-based over water-based paints.

Wayne

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Posted by Omaha53 on Thursday, January 11, 2018 11:44 AM

I would agree that high humidity can cause this. It has happened to me when I used the rattle can in my shed early in the day when it was foggy outside. I applied another coat later in the day when the humidity had decreased and the milkiness disappeared.

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Posted by Howard Zane on Thursday, January 11, 2018 12:04 PM

Interesting.....I am not sure as I know enough about model painting to be dangerous, but I think most dull lacquers have talc added as the dulling agent. I have found inconsistencies in Dullcote over the years.....so much so, that I stopped using it. It seems to work OK on wood, but on smooth surfaces such as painted brass or styrene, sometimes you'll get spots or talc stains. Both airbrushing and rattle cans caused this condition, but airbrushing a bit better as thinner was added.

HZ

Howard Zane
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Posted by BATMAN on Thursday, January 11, 2018 12:13 PM

I had an issue with rattle can stuff doing that. I had left the can out in the garage and it was cold when I used it. I went in and got my other can that had been kept in at my hobby desk and it was fine. I had bought both cans at the same time. Being cold and/or constant temperature swings were probably the cause of the problem.

Brent

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Posted by NVSRR on Thursday, January 11, 2018 2:21 PM

I had that issue once apon a time Using testors laquaer. Found it was the mixing ratio of thinner to base. Also type of thinner and base.  If they are not from the same producer,  they dont always play well together with the clear Coat.   Since you are using automotive laquaers, all i can say is paint big piece of scrap plastic. And start mixing clear coats.  Starting at 20/80 and working up by 10s. 30/70, 40/60 and so on. make sure to divide the plastic sheet and mark off the section with the ration so you can watch over time what happens.   That what i had to do to finally find the right ratio so that didnt happen

 

Wolfie

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Posted by ROBERT PETRICK on Thursday, January 11, 2018 2:37 PM

Ever notice when you release the valve on the bottom of the air tank there is some moisture that comes out? Do you have a water/moisture trap on the line between the compressor and the air gun? Not critical when spraying acrylics, but important when spraying solvent paints. Under pressure water/moisture mixed with solvents form emulsions, which can be milky.

Robert

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Posted by MisterBeasley on Thursday, January 11, 2018 3:24 PM

I've also had the problem with humidity.  I sprayed two identical shells outside on two different days, from the same rattle can.  The humid day produced a milky result, while the dry day did not.

I kind of liked it.  One just looked cleaner than the other.

It takes an iron man to play with a toy iron horse. 

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Posted by BigDaddy on Thursday, January 11, 2018 5:23 PM

Alcohol on top of Dullcote, turns white, but that is not what you described.  Dunno.

 

Henry

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Posted by CHARLES A TREVEY on Thursday, January 11, 2018 5:32 PM

Thanks for all of the replies. I live in north Florida and the weather was rather damp on that occasion. The project was a previous coal hopper which was painted with scalecoat 2 and completely dry. I sometimes blend glosscote and dullcote to get various satin finishes however this was straight dullcote purchased in about 2015. I have noticed that there seems to be some additive (perhaps talc) that I try to mix completly. I think that I will repaint this car under different conditions and see what happens. I have noticed that scalecoat now has their own brand of clearcoats which may prove to be more consistent.     

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Posted by Mark R. on Thursday, January 11, 2018 6:32 PM

Can be caused by a couple things - most common is humidity. Another cause is the talc to carrier ratio is too high - the talc doesn't get fully immersed in the carrier on the surface and the result is you are seeing the dried talc.

Another coat of finish or even a straight shot of thinner will make it disappear. 

That being said, that white haze can also be a very convincing weathering effect once you learn how to control it. This is a factory painted Athearn Genesis that was faded using the hazed dullcoat as the base fade ....

Mark.

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Posted by bodgybuilder on Thursday, January 11, 2018 8:22 PM

As others have said, I have found it to occur in high humidity, and occasionally use this feature for factory painted locos.

It pays to make sure the dullcote is properly mixed prior to decanting to thin and stays mixed while airbrushing. The talc settles out if it sits.

Matthew

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Posted by SeeYou190 on Thursday, January 11, 2018 8:58 PM

This is a real issue in South Florida where the humidity is very high for 7-8 months out of the year. We cannot spray Testors 1260 Dullcote for weeks at a time or the dreaded white haze will be the result.

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The good news: The problem is easily fixed most of the time. Just wait for a dry day, give the can of Testors Dullcote a real good shake, and spray on a light coat onto the effected model. It should be OK.

.

Welcome to the Model Railroader forums.

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Good luck!

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-Kevin

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Happily modeling the STRATTON & GILLETTE RAILROAD located in a world of plausible nonsense set in August, 1954.

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Posted by 7j43k on Thursday, January 11, 2018 9:01 PM

This phenomenom can be found with the search terms:  "spray paint" humidity blushing blush.

 

I think the result of this discussion is don't spray paint with high humidity.

 

Ed

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Posted by CHARLES A TREVEY on Friday, January 12, 2018 11:22 PM

Thanks to all for the replies. They have provided some options and possible solutions for this problem. As shown, it seems to have some unexpected weathering qualities as well. 

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