I inherited a rather old Iwata Revolution a while ago, which should be a big step up from my much more basic one. However, after some initial success and then a break, I'm struggling to get it to work.

Symptom: Pushing the trigger down, in any position, causes air to rush out of the nozzle as usual. Pulling the trigger back leads to a backflow of air into the cup, causing the paint to bubble, and no paint comes out of the end.

What I've tried: Complete disassembly and cleaning with lukewarm tap water. Attempted to spray both water and acrylic medium, but both exhibit the problem described above. Visual inspection found all parts appear clean, uncorroded and undamaged. Pulling the needle back by hand (instead of using the trigger) produces the same effect.

Background: The needle and nozzle are both quite new (I had to replace them). I had it working quite nicely early in the year but it's been unused for 2-3 months. It was thoroughly cleaned and disassembled before this break. I mostly used it for acrylics; I'm not sure how the previous owner used it but I believe he would have taken reasonable care of it.

Any ideas about what else I could look into?

UPDATE: On @fixer1234's advice I took it apart and gave it a 4-hour soak in hot water and dish soap, replacing the water with freshly-boiled water when it went cold. I then soaked all the parts except the main body in denatured alcohol for another couple of hours. No change unfortunately. I could repeat the latter process but the parts are already gleaming and it's hard to see what I'd be trying to achieve.

  • The mechanism is pretty simple. If the parts are undamaged and clean, they ought to work. Just a guess from your description: there may be dried paint plugging something internal. Once the paint dries, water or acrylic medium won't dissolve it. You would need something to attack it chemically (which can take a very long soak, maybe in an ultrasonic cleaner, if its inside a tiny orifice), or appropriate size cleaning wires.
    – fixer1234
    May 31, 2022 at 19:14
  • 1
    Can you give details about your air supply? It could also be that the air is sufficient for you to feel it, but insufficient to pull the paint or water in your tests. Have you tested at differing pressures?
    – SNSAD
    Jun 1, 2022 at 13:18
  • @fixer1234 A long soak sounds like a good idea. I'm not sure whether there are rubber parts inside the man body so am a bit nervous about using alcohol / other solvents in case of incompatibility.
    – helveticat
    Jun 1, 2022 at 20:32
  • @SNSAD That's a good thought but I've tried a wide range of pressures and the same compressor is driving my other airbrush just fine, so I don't think it's that.
    – helveticat
    Jun 1, 2022 at 20:33
  • re: update -- if the problem is dried paint in some internal spot, hot water and soap won't affect it. Denatured alcohol can work if it's in contact long enough. If it's in a thin tube or orifice, that could take a long time. The outside surfaces looking clean wouldn't tell you anything about any internal paint. If everything is straight paths, you could check to see if light passes through, or see if you can pass a fine wire through.
    – fixer1234
    Jun 6, 2022 at 14:20

1 Answer 1


According to the manual bubbles in the color cup can be from:

  1. Loose nozzle cap
  2. Improper nozzle to body connection
  3. Cracked or damaged nozzle


  1. finger tighten the nozzle cap
  2. reseat the nozzle
  3. replace the nozzle

If its not dried acrylic paint it is probably one of these.

  • Nozzle is a ridiculous word.
    – rebusB
    Jun 6, 2022 at 13:37
  • It is indeed a silly word... Well it's certainly possible the issue relates to this but in this case the nozzle and cap (if that's what it's called) have been recently replaced and very thoroughly cleaned so I'm leaning towards the theory that it's some dried-up paint inside the body. I'll update if / when I find a fix...
    – helveticat
    Jun 7, 2022 at 15:23

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