My Tamiya (Iwata) airbrush spits paint from time to time. Am using Tamiya acrylics thinned 60 percent with 91% isopropyl. Shooting at 20 psi. This has been happening for the past few months but now have time to build more kits.

It's not water in the line because it's paint coming out. (I have had condensation issues in the past so I know what that looks like.)

I notice a slight bend to the needle and have straightened out as best I can. Could this cause the problem? If so, I'll get a new needle.

Also, I do clean regularly near the tip so it is not paint build up.

What do you think? I'm itching to finish my Monogram B-25H.

Thanks much,
Mike J

Mike Witous

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You might want to get a new needle and make sure the cone or cap that the needle fits into isnt cracked or dinged.

And 20 psi is a bit high. Especially for detail work you can spray down around 5-10 psi under load.

A cracked or deformed cap (where the needle seats) will cause spitting and spattering as will a bent needle. Some times you can strighten a needle by rolling on a glass plate. Unfortunatly there's no cure for a cracked air cap.

or a crack in the tip. A hooked needle would cause the occasional large droplet to be "spit" onto the model, while a cracked tip would cause the paint flow to sputter and spit erratically.

If you got a hooked needle you could have cracked the tip pulling the needle back through it to remove it. If it's a Tamiya Superfine, it's very likely, those .2mm's are very delicate. If the tip is OK, but there's still a little hook on the needle you can straighten and polish it out, but that's a skill all onto itself. Just google polishing airbrush needles and you'll find many different ways to do it. It's not for the faint of heart...

Drag the tip of the needle at a low angle across a thumbnail or cutting mat while twisting the needle at the same time. With a little practice you can straighten it pretty well. If done repeatedly (bend/straighten cycle) the needle will begin to have a slight corkscrew-ish look to the very end, and should be replaced. I should mention that this works on my Paasche needles-

You cannot straighten an Iwata needle back to where it was. They are very precise. Also, your nozzle may well be damaged. I would at minimum look at it under magnification, or just replace it to be sure.

Hope this helps.

Scott Gentry

PS I also shoot Tamiya acrylics at about 15 psi.

...off of your regulator. You mentioned condensation, but not if you had a water trap on your air hose line. It works wonders.

I've had an Iwata HP-C for many years now and whenever it begins to spit it is because of paint build up in the channel between the cup and the nozzle. When I first experienced this spitting problem I was perplexed as to why it was happening. I thought that I had been taking good care of my brush and cleaning it thoroughly after every painting session. I thought it might be a bent needle or a split nozzle, but I couldn't come up with an answer. So, I packed it off to Medea in Portland to have one of their technicians look it over for me. He said my problem was dried paint build up and that I needed to scrub the channel regularly with a interdental brush. He was right. I've not had a spitting problem that continued after scrubbing out the channel with an interdental brush and lacquer thinner. Interdental brushes are made for people who have braces or bridge work on their teeth. You can find them in any well stocked drugstore. You may think it's not paint build up but it doesn't take very much to cause spitting. Take off the nozzle and run the interdental brush through the channel several times with some lacquer thinner. I believe it will take care of your problem. -- Dave