Why is acrylics spraying splattery?

[Milo]

I'm airbrushing with some acrylic testors but it's always coming out splattery. It either comes out nicely, but then beads up on the model, or it just shoots out splattery. Both have happened.

[ctruss53]

I can't tell you for sure what is happening when your paint beads up because I don't know what conditions you are spraying in.

However, in the past when I have had acrylic paint come out of my airbrush splattery, it is one of two things, or a combination of the two things.

1. Not enough air pressure.
2. The paint is too thick.

For condition 1, look online for a suggested air pressure setting.  If you can't find one, I like to start at 20psi and adjust from there. Unless you are doing close-up detail work, it is pretty hard to have too much air pressure.

And then if your paint is too thick it will not atomize properly. It will come out splattery and it could clog your airbrush up.

Then it could be a combo of both things.  Like your paint might be too thick, but only a teeny bit too thick and in some cases uping the pressure can fix it.

I hope this helps.

[Milo]

I was thinking that it was too thinned. But when I didn't thin it it just didn't even spray. I'm thinning it with water about 1:1

[ctruss53]

Who makes the paint? Because every paint is different.

 

EDIT: Oops, you said who makes the paint.

Edited June 22, 2023 by ctruss53

[ctruss53]

I did some quick searching. Found all kinds of conflicting info.

According to Testors, if you are using Model Master Acrylic, they say you shouldn't have to thin it.  I doubt this because I have brush painted with it. So it has to be too thick.

Then when I looked for the best thing to thin it with I see people suggesting Windex.  I'm sorry, Windex might work, but I would never put something designed to clean windows, in paint.

It appears Mr Hobby Leveling Thinner works.  I would actually consider this. I have heard nothing but great things about that stuff.

And if Mr Hobby Leveling Thinner works, then Tamiya X-20A Acrylic Thinner would work. That stuff is great.

And if Mr Hobby Leveling Thinner works, which meand Tamiya X20A works, then Mission Models Thinner will work great as well.

 

Short answer. I think you can use any lacquer thinner. And the general rule of thumb is thin to the consistancy of skim milk. Whatever that means.  haha

[Milo]

I have no idea the thickness of skim milk ? but anyway windex fixes everything (thats from my big fat greek wedding)

[Dave G.]

Thinning with water in most any acrylic paint and then airbrushing is never optimal . Nix the water or at least water alone. In Testors I find my own mix of thinner to work best but then I have a whole system of shooting acrylic paints that I doubt anyone else follows.

Here's the deal from another view though, Testors makes their own acrylic thinner, try that first.

Don't forget to use a decent primer on your model as well.

Edited June 22, 2023 by Dave G.

[DanR]

33 minutes ago, Milo said:

I have no idea the thickness of skim milk ? but anyway windex fixes everything (thats from my big fat greek wedding)

I'm with you. How the heck do we know the thickness of milk? As a rule of thumb, I once saw that if you drag a small line of thinned paint up the side of the paint cup, and it's not watery and running down the side, nor is it sitting there in a lump at the stopping point, you're likely ok. You should have a clean, even line of color that basically hangs there.

[Dave G.]

32 minutes ago, DanR said:

I'm with you. How the heck do we know the thickness of milk? As a rule of thumb, I once saw that if you drag a small line of thinned paint up the side of the paint cup, and it's not watery and running down the side, nor is it sitting there in a lump at the stopping point, you're likely ok. You should have a clean, even line of color that basically hangs there.

The mixing stick thing works quite well actually. Drag a good batch of paint up the side of your mixing cup with the mixing stick. It should return down the side of the cup in 1-3 seconds or so and leave a film behind. If it returns instantly with nothing on the cup then its too thin. If it sits like a blob or creeps it's way back down it's too thick. You don't have to be exact and can change air pressure for the difference. Also this depends on your thinner mix in terms of any additives, the brand paint as well. Some paints just flow out a little better than others and this is something you get a feel for. Thinning this way is thinning by viscosity. But once you get a good repeat going on with this you get a sense for what ratio you hit on for that color.

But that range of thickness above will get ya going. Some paints like the thinner side of that method, others will take the thicker. And if it doesn't want to spray out right it may still be a bit thick,just put in a few drops more thinner, it will probably spray fine..

I've sprayed low fat milk by the way, to entertain myself. Swirled it around in the cup, got a sense for it, put it in the airbrush and it sprays great. But so does water or alcohol or lacquer thinner if you think about it. So when your paint won't flow it's probably too thick.

Edited June 22, 2023 by Dave G.

[ctruss53]

Like Dave said, thinning with water might work, but it isn't optimal.

I thin Tamiya Acrylic paints with water, and it seems to work just fine. However, Tamiya acrylic paints are the only acrylic paints that seem to work with water. Every other acrylic paint I have tried to thin with water just don't act like they should.

The skim milk thing.  I just said that as a joke. Because everyone and their moms all say to thin paint to the consistency of skim milk.  I don't know what that looks like in a paint cup. I have never had milk in my paint cup. So I think it is funny.

What I do is similar to something Dave said. I thin the paint at 1:1 to start, unless there is a recommendation from the manufacturer. Once I mix the paint up with thinner, I pull my stir stick out. If the paint flows down the stick and drips off pretty easily, I would consider it about right. If it runs right off, it is probably a bit too thin.

If you are painting whole parts, and not trying to do close up detail work, it is ok if the paint is a little too thin. If it looks a little too thin, just apply it in light coats. And if it is too thin, don't be shocked if it takes several coats for even coverage.  I guess what I am saying is you can work with paint that has been thinned a little too much, so it might be better to error on the too much thinner side. if it looks a little too thick, add a little more thinner.

[Sidney Schwartz]

These days I use craft paints 95% of the time. These of course need thinning as they are normally quite thick. It took me a long time to get the hang of thinning paints (and using an airbrush in general), but with time and patience I got the hang of it. I first I tried some of the tricks mentioned here, like dabbing the paint on something and timing how long it took to drip down X distance, etc. Nowadays I can usually nail the paint/thinner ratio, or get very close, just by looking at the paint as I mix it. But mainly I let the airbrush tell me what needs to be done. For what it's worth here's some of what I've learned.

1. I have a Paasche airbrush. I always use the size 3 (.73mm) needle. I've also tried the .55mm and 1.06mm needles and this is the one that works best.

2. I set my compressor at 20 psi and leave it there. My experience has been that if I thin the paint correctly, I should never have to change needles or psi setting.

3. I use Vallejo airbrush thinner. I've also used water, wiper fluid or Windex (alcohol), Liquitex airbrush medium, and probably others I've forgotten. The Vallejo seems to work just fine and it's inexpensive. 

4. I use one of those battery powered paint mixers. Thorough mixing is important and the mixers are cheap. 

5. I'll start with about a 1:1 ratio of paint to thinner and add more according to how the paint looks...this just takes experience.

6. ALWAYS test spray. IMO this is the only way to tell if you got it right or need to adjust. I keep a stack of index cards cut in half and use those for testing. I look for a few things when testing. A) I should not have to pull back the airbrush trigger more than about halfway before the paint starts to spray. B ) The sound of the paint spraying should be even with no hesitations or stutterings. C) The spray should be 100% even with no blobs or spattering. D) The paint on the card (held vertically) should not drip or run, but also cover well.

The most common problem I'll have is that the paint needs to be thinned more. I keep a jar of water at the work station and use that the flush the too heavy paint out of the airbrush, thin the paint some more and re-test. In rare cases I'll have to disassemble the airbrush and give it a more thorough cleaning. 

This all sounds complicated but it goes very quickly. I can't imagine it taking me more than five minutes to get the paint properly thinned and ready to spray. Keep at it...it gets easier.

 

[peteski]

3 hours ago, Sidney Schwartz said:

Windex (alcohol)

"Standard" Windex is ammonia (not alcohol) based.  They might have another version that is alcohol based, but when someone mentions "Windex" my first thought is "ammonia".

[Sidney Schwartz]

3 hours ago, peteski said:

"Standard" Windex is ammonia (not alcohol) based.  They might have another version that is alcohol based, but when someone mentions "Windex" my first thought is "ammonia".

You're right. Forget that part. ?

[vintagerpm]

My advice  is to always thin paint with the thinner made for that paint. While other products "might" work, why go through the hassle of failed spraying to find out. No two paints are formulated exactly the same.

[ColonelKrypton]

1 hour ago, vintagerpm said:

My advice  is to always thin paint with the thinner made for that paint.

Excellent advise.  Anything else is a false economy and brings to mind the old idiom "penny wise and pound foolish".

cheers, Graham