Weird specks in my acrylic airbrush finish... what to do?

[Marc_G]

Hi folks, a few pics are worth many words and tears.

My Ranger in opaque white (Createx Wicked Colors). It was nice and smooth:



After the first coat of Wicked Yellow (10% thinned with wicked reducer). Nice and smooth:



After the second coat 90 minutes later, suddenly I noticed weird specks in the finish:



After drying, they are less prominent, but still there:



Any idea what these may be, and best way to get rid of them? I could take a 400 grit paper and maybe scuff them off, and lay down another coat, but I'm worried since I don't know what caused them in the first place. Paint was from the same mixed batch. Airbrush was clean. The specks are all over the finished piece.

Ideas?

Marc

 

[kjohnson]

Splotching is usually one of three things- media needs to be thinned more, air pressure isn't right (need more for bottom feed), or the tip is getting flooded by not shutting off the paint before the air (for dual action brushes). Tell us a little bit more about your setup.

kj

 

[jsargevt]

Do you have an inline air and moisture filter on your airbrush (assuming that you're using a compressor)? I was having issues with "crap" coming out once in a while - I'd be going along nice and smooth and then I'd get this odd splotch. Turns out it was drops of water mixing in with the paint.

I am sure that you have thought of this but if you have not it might be worth checking out.

 

[Marc_G]

It's a Paasche H single action fed by the CO2 tank. So no need for moisture trap. Pressure in upper thirties with the H5 tip.

In a year of airbrushing this is the first time I've seen anything like this. And I've used the same bottle of paint before with no trouble. And the first coat went on fine.

Im nervous about truing to sand down the bumps since acrylic paints don't dry hard. Wondering if I should just leave it.

Marc

 

[kjohnson]

Depends. I know folks that would be bothered so much by that they would have to sand it all down. Are you planning on making that a display model or one that flies a lot? If it's built to fly a lot, I would leave it. If it's supposed to be a showpiece, then sand it all back down.

kj

 

[mkadams001]

That looks like solvent pop which happens when the undercoat is still outgassing. Sand it and paint again.

 

[Marc_G]

Undercoat of sealer white and opaque white were both way dry. The more I think about it the more I wonder if I was getting a tip dry phenomenon. During the first coat that didn't get bumpy specks, the nozzle periodically clogged an paint stopped coming out. I twisted it on the needle screw and wiped residue off then proceeded. Happened maybe four times in the first coat.

Second coat did not clog up but maybe dried bits were spraying off the nozzle and into the wet paint surface.

Tonight I will see if I can lightly sand and knock the specks down to make flat surface for another coat or two.

 

[Marc_G]

Ug! That did not go well.

I sanded down the paint job just a bit thinking to knock off the high spots. All I really did was smear sandpaper crap into the paint job. These acrylic paints when dry are flexible almost to the point of being sticky and don't like to be sanded.

I eventually gave up, having added some dark colored streaks and such to the yellow paint job. Then I sprayed with a slightly more thinned batch of the paint and it ran like crazy, and gave the same specks at the same places and probably some more. Looks terrible. Can't really sand the stuff off without major effort so I'm just going to let it dry and call it yellow. Once dry it probably won't look quite so bad. Probably.

Lesson learned: start with the airbrush more closed and then later open it up if all goes well. I was applying the paint way too heavily.

Later tonight, when the yellow is more or less dry, I will see about getting the nose cone painted red. That will leave just the black to be done, and I want the yellow to be super dry before I try to mask the adjacent yellow. I'll give it a full day which is a long time in acrylic paint world. Might take a hair dryer to it tonight (Wicked colors can be heat-set, or just leave them sit for a while).

Marc

It's a shame because I was trying to be careful with the prep work.

 

[Marc_G]

So, it's more or less dry. The specks aren't terrible and I'm letting it go. The runs in the paint are actually more annoying, but they are not bad either, due to some delicate paper dowel blotting work when the paint was still wet. Too wet. I learned my lesson.

I did red on the nosecone after the yellow was dry; I didn't thin at all and used light misty applications. Went on like a charm. No specks, good coverage, looks great. See it here.

The imperfections in the yellow will be very hard to see, when the rocket is hanging 40 feet in the air, dangling from a branch...

 

[foamy]

Hey Marc, are you leaving the paint in the spray bottle between coats? Are you mixing it good before you spray again? Are you leaving the suction tube in the bottle?

Just wondering, as paint will settle in the bottle and can be sucked up in chunks. Same goes for paint coagulating on and in the suction tube etc. What do you thin with?

 

[jsargevt]

The imperfections in the yellow will be very hard to see, when the rocket is hanging 40 feet in the air, dangling from a branch...

Words I live by when painting. I aim for a decent finish, and when it comes out less than perfect and I start to get frustrated trying to fix it - I pull that phrase out.


Mostly because it is absolutely true.

 

[Marc_G]

Hey Marc, are you leaving the paint in the spray bottle between coats? Are you mixing it good before you spray again? Are you leaving the suction tube in the bottle?

Just wondering, as paint will settle in the bottle and can be sucked up in chunks. Same goes for paint coagulating on and in the suction tube etc. What do you thin with?

I was using the little quarter ounce metal cup. I rinsed it out between coats and even cleaned the needle. The paint (thinned a bit) was in a small plastic jar with a plastic top to keep it from evaporating. I shook up the paint again before pouring it into the metal cup for the second coat.

I think there were several problems. First, I shouldn't have thinned the paint, at least not so much. Secondly, I think I was getting some tip dry and bits of dried paint were flying off the needle into the work.

I've subsequently painted with Wicked black and red just fine by not thinning at all, and dialing down the brush so less paint came out. I got a better mist and lighter coverage but in several passes not one such fleck. I think I just learned better technique.

Marc

 

[foamy]

snip...I think there were several problems. First, I shouldn't have thinned the paint, at least not so much. Secondly, I think I was getting some tip dry and bits of dried paint were flying off the needle into the work.

Sounds logical. I haven't thinned any of the Createx yet. I kind'a thought it was thin enough as it was. I haven't bought/used any Wicked colors as yet. Glad you got it sorted out.