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Hi guys,

My airbrush is playing up...
Last night, it started 'spitting', for lack of a better word. When spraying the paint/water/cleaning fluid it sprays a bit, stops then sprays more very rapidly - instead of having a continuous, unbroken spray. At the same time, bubbles are forming in the cup. I cleaned it a few times last night, but the problem persisted. It was getting late, and I was tired so I gave up then. I came to it again today, and after re-cleaning the airbrush, the problem is still there. What the hell is causing the problem? The fact that air is going up through the cup makes me wonder if its something wrong with the needle cap.

I'm certain that it's not a case of cleaning it. I'm also certain that the paint is flowing through the airbrush properly. The needle isn't bend, either.
I've not had a problem that wasn't solved by checking the above^.

I appreciate all your help
Z

if its not a cleaning issue the only thing that I could think it was is irregular air pressure coming from the compressor or human error.

When Ive had spitting before is when their have been undiluted paint at the base of the brush and where I've added thinner above it hasn't reached all the way to the bottom. Which gives very slow barely existent spray until the 'blockage' is gone and then all of a sudden gushes because I've been holding it down too far trying to get the non-thinned paint out.

'I'm sure it's not a cleaning issue' is the airbrushing equivalent of a teenager saying 'I've never been sick from alcohol', whilst clutching a 2 litre bottle of White Lightning.

So, time to break out the newspaper and cover the bathroom floor.

The bubbles are indicative that air is not reaching or exiting the atomisation chamber. This chamber is formed by the nozzle cover, just behind the nozzle cap. If it's not apparent when removing the nozzle cap, then it's probably further in toward the air inlet to the chamber. If air comes out the front, but no paint, that's usually a sign of a paint clog in the nozzle.
9 times out of ten this means strip down, and clean it properly. I have VERY RARELY managed to sort it by shooting through solvent and 'blowing back' or brushing solvent around the nozzle and airbrush body after removing the nozzle cap. You may find several cycles in an ultrasonic cleaner do the trick, and that's my go to solution when my AB starts to misbehave.The ultrasonic is more reliable, take longer, but is far less likely to pooch your o-rings. Unless you're nifty with the PTFE, you need to look after those o-rings.

You have a water trap in your line?

Most compressors are going to create water that can get in the air hose and that can cause your spitting.

Yeah, but water in the line tends not to cause the bubbling in the cup.

Disassemble your airbrush at the atomizing chamber it should be several pieces at the business end of the airbrush, you need a good set of cleaning rods and you can use the tip of your airbrush needle to get into the nitty gritty of cleaning out the inside of your nozzle as I suspect there is where your blockage lies. You can solve this or delay this at least if you are lazy at cleaning out your hardware by using vallejo air line of paints or learning to properly mix your paints by going for a milky consistency.

Be careful with using your airbrush needle to squeeze out old paint and only do it after a good soak in cleaner so it just slides out, most needles are 10$ to replace.

I wouldn't recommend reaming out your fluid nozzle with any object. Additionally poor performance like this can come from an improperly secured fluid nozzle.

But more likely is because your nozzle is clogged. Put on your safety stuff, respirator and gloves and soak it in acetone, denatured alcohol or lacquer thinner. If you can shoot a little of the solvent through your airbrush after you soak the nozzle in solvent. Make sure you can do it safely with proper ventilation and no pets or loved ones nearby. If that doesn't fix it take a close up of needle and nozzle and inspect for damage.

Tyronus Fruitridge Powers wrote:
I wouldn't recommend reaming out your fluid nozzle with any object. Additionally poor performance like this can come from an improperly secured fluid nozzle.

But more likely is because your nozzle is clogged. Put on your safety stuff, respirator and gloves and soak it in acetone, denatured alcohol or lacquer thinner. If you can shoot a little of the solvent through your airbrush after you soak the nozzle in solvent. Make sure you can do it safely with proper ventilation and no pets or loved ones nearby. If that doesn't fix it take a close up of needle and nozzle and inspect for damage.

I must agree. There is also a product by Mr. Hobby called Mr. Tool Cleaner that is a crazy, acetone-type solvent that just eats paint. It works very well on nozzles and caps to loosen the paint (ultrasonic or brush it after); however, it will wreck rubber o-rings, so don't put it in contact with any of those. It also smells to high heaven, so it's important to use it in a well ventilated space (just like acetone). It is not expensive; about as much as nail polish remover.

Okay, my two cents learned the hard way:
(BTW NEVER use the needle to clean with, you are messing with how well the spray works: any slight bend and it will be irritating).

Spitting and bubbling air brush:

1) (most likely) Depending on the model, how well the cone is seated is also a likely culprit for air to feed back in: make sure the back mating surfaces of the cone is clean and if using a screw / o-ring seal, make sure that is clean and properly tightened down.

2) Make sure the needle fits all the way in (fully seated). If you tighten the needle too far back it will continually feed a bit of air.

3) Too thick paint tends to clog up the works and prevents the needle seating properly as well.
What nozzle size you using?
If it is in the range of a 0.2 to 0.3mm make sure they are airbrush specific paints, nice and liquid and no dried bits in it (running through a screen may be an idea).
I was using an automotive acrylic paint and it was garbage until I used a 0.5mm nozzle and then all was well: right viscosity vs. right nozzle size.

4) (less likely) Make sure the needle is cleaned and possibly lubed: any dried paint will prevent a good seal and the compressed air can go into the cup.
Look at the mating surface for the needle that keeps back the air: it too could have some contaminant or paint preventing a good seal.

Good luck!

Thanks all for the advice, very helpful for general knowledge.

However, I've been investigating the problem and think it's the actual airbrush that's broken. When the trigger is pushed down (and NO paint is released - the needle is all the way forward), there are still bubbles in the water in the cup. It leads me to believe that there is air getting through the airbrush without going through the nozzle.

Then I found this:


There isn't a snug fit between the airbrush and nozzle.
But now I'm baffled, for a few reasons:
1) I dont remember any significant trauma to the airbrush leading up to the start of the problems that would be enough to damage just the connecting bit. I did drop the airbrush, it fell two foot and landed on it's side, but that wouldn't cause significant damage to a thick (in terms of airbrush pieces), circular piece of the brush and not damage the needle cover too.
2) And, would this really be the root of all my problems? I mean, sure the air could get through there and cause the bubbles in the water. But what about the threads? Surely that'd hold the air out. Can this even cause the spitting problem?

Thanks,
Z

Winterdyne is the man to listen to here.
But to me this sounds like a twofold problem.
One being a clogged nozzle. Which a good clean will sort out.
The second one seems like it might be a trigger issue.
Have you lubed your trigger assy. lately?
If not try it.

I recognise that nozzle fit.

Looks very much like an O-ring is missing from the nozzle.

Two ways to fix it:
First - get a new o-ring and/or nozzle.
Second - get some PTFE tape and carefully wrap a bit around the thread of the nozzle and build it up to form a seal behind the 'lip'. This will be awkward to centre in your nozzle cap but it is doable.

You're also missing the sealing o-ring from the nozzle cover / atomisation chamber. That will also either need a new o-ring or wrapping with a bit of PTFE to make a good seal.

Talys wrote:

Tyronus Fruitridge Powers wrote:
I wouldn't recommend reaming out your fluid nozzle with any object. Additionally poor performance like this can come from an improperly secured fluid nozzle.

But more likely is because your nozzle is clogged. Put on your safety stuff, respirator and gloves and soak it in acetone, denatured alcohol or lacquer thinner. If you can shoot a little of the solvent through your airbrush after you soak the nozzle in solvent. Make sure you can do it safely with proper ventilation and no pets or loved ones nearby. If that doesn't fix it take a close up of needle and nozzle and inspect for damage.

I must agree. There is also a product by Mr. Hobby called Mr. Tool Cleaner that is a crazy, acetone-type solvent that just eats paint. It works very well on nozzles and caps to loosen the paint (ultrasonic or brush it after); however, it will wreck rubber o-rings, so don't put it in contact with any of those. It also smells to high heaven, so it's important to use it in a well ventilated space (just like acetone). It is not expensive; about as much as nail polish remover.

I normally replace the rubber O-rings with EPDM O-rings. Places like McMaster-Carr or Small Parts (now consumed by Amazon) will have what you need. Measure a new one from the manufacturer, or have a drawer full of them to test fit to find the right one. Many of the paints I use will eat through rubber on their own. If the machining of the parts is fine enough, you may even be able to upgrade to Teflon seals as opposed to O-rings (either solid, or compressible). About the only thing that eats those is fluorine gas.

I paint without the needle cap/crown and constantly clean off the needle tip while painting. This will help with the spitting issue and back-pressure causing the bubbles in the cup.

Between colors, I rinse out the cup under a faucet. When the water is clear, I hook back up to the compressor and block the tip so that anything left in the tip gets ejected back to the cup.

I do recommend an Ultrasonic Cleaner. They sell for about $40 and do wonders for cleaning the airbrush parts as well as stripping models.

The picture shows exactly the area I figured would cause getting bubbles in the cup.
There is no cross-threading with that end right?
It looks an awful lot to one side.
If it is not straight, the needle will have a harder time seating properly and your spray will tend to one side (faster build-up as well).

Some sealing gasket or o-ring does look like it is needed.
A small amount of Teflon tape (the white plumbing stuff) may keep you going until you get the proper part.
If it does not fit well, a very weak bond Loctite sealer could help (or rub some wax on the threads).

Good luck.