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Old 03-12-2008, 05:42 PM
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Grim Jim Grim Jim is offline
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Airbrushing advice... please!

Hi all,

I am getting back into the hobby after a hiatus of a few years.
I have an old Aztek airbrush that I used fairly happily before packing it away when I stopped modelling. Now I am trying to get it working again and having major problems.

What is happening is that the paint will flow properly for, say, ten or fifteen seconds, and then just fade out. Then I am finding that the only way to get any paint to flow at all is to push the trigger all the way in and all the way back. And then that fades out after a few seconds, too. After that, the only way I can get any paint to flow is to kind of "pump" the trigger backward and forward.
If a clean off the nozzle with a clean paintbrush, I can get back to the original state, but then it all fades out again.

I am assuming that my nozzle is clogging because the paint is drying in it too quickly. I don't remember having this problem before packing everything away, though.

I'm using Tamiya acrylics, thinned with water or screenwash (I've had good results with screenwash in the past). I've tried every consistency of paint from "straight from the pot" to "thinned so much that there's no paint left", and get the same result.

If anyone has any advice or ideas, or can just tell me what I'm doing wrong, I'd be very grateful!
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Old 03-12-2008, 10:43 PM
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greybeard greybeard is offline
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If you've experimented with different viscosities of paint, the the problem is likely airflow, unless there's something inside gumming up the works. You might try running some lacquer thinner through it to dissolve any paint buildup inside.

Have you taken it apart to see what condition the grommets are in? Is the inside squeaky clean? What is your air source?

Scott Fraser
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Old 03-13-2008, 03:40 AM
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Grim Jim Grim Jim is offline
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Thanks for the quick response, Scott. I think I will have to try the lacquer thinner approach as you suggest.
I can't really get the brush apart to get to the grommets. Or at least, I can, but I'm pretty sure that I will destroy it in the process. So I suppose it's possible that they're perished or damaged. Although they shouldn't be - these Aztek brushes are supposed to last a lifetime.

As for its being squeaky clean; no, I don't suppose that it is. But it should be fairly clean, because I've had a couple of long cleaning sessions to try and sort this out. But I have been using water, so your suggestion of thinners would probably help here, also. The nozzle assembly I'm now using is brand new, so there shouldn't be a problem with that.

My air source is my old Sparmax compressor. It seems to be working as well as it ever has. Once I have cleaned the airbrush, I can spray water with it quite happily. But as soon as I put paint in it, I get the same problem.
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Old 03-13-2008, 05:08 AM
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greybeard greybeard is offline
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Okay, so nozzle is not clogged, needle should also be new, eh?

Look carefully at how it went together — that's how it comes apart. For my (old) Binks, I have a tool they sold at one time to remove the screw that fits into the body of the part the nozzle threads onto (I'll call it the mixing cavity), without damaging the inside threads. That's how I remove the threaded ring that retains the grommets.

Strictly speaking, it shouldn't be necessary to remove or replace the grommets unless they've deteriorated from exposure to reactive thinners. That said, the interior of the mixing cavity should be squeaky clean to avoid interference with the aerodynamics of the venturi the airbrush is built around. If it's obstructed, it won't draw paint well, which sounds like what is happening.

You can try soaking it in solvent (do not leave it for more than an hour or so!) and then fish a fine wire inside and see if it comes out with any sludge. If it does, you've found the problem. It may just be a lump of hardened paint that's moving forward once the air starts flowing and blocks the needle valve. Gentle probing will perhaps confirm that.

Good luck! Airbrushes are wonderful, but they can be a real pain!

Cheers
Scott
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Old 03-14-2008, 01:16 AM
Evan August Evan August is offline
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LQ mentioned a product by Gunze called Mr. Tool Cleaner, or something like that, when I was looking for pointers. Apparently it's top notch stuff for cleaning Airbrushes. Just passing it along...
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Old 03-14-2008, 11:47 AM
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Grim Jim Grim Jim is offline
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Scott and Evan: thanks for your advice. I'll try and get some kind of solvent at the weekend, and give it a good soak. I only have a wee jar of Tamiya thinners, and that's not going to be enough to do the job, I think.

Scott, the reason I'm having trouble taking the brush apart is that it's an Aztek. They're different to "ordinary" airbrushes, in that they use a sealed nozzle assembly that contains the (very short) needle, spring and nozzle. The nozzle screws into the front of the plastic airbrush body. In theory, it makes it much easier to keep clean, and also protects the needle from damage. In practice, though, I'm not convinced. It just seems to make it that much harder to clean in thoroughly. The body is made of two plastic pieces that snap together. I think that if I try and get them apart, the operative word is likely to be "snap"!

Anyway, I'll give it a go with something stronger than water, and let you know. And if it doesn't help, well, it's a good excuse to go and get that Iwata I've had my eye on...
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Old 03-14-2008, 05:20 PM
mic bradshaw mic bradshaw is offline
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Be careful Jim,

Azteks do not take kindly to solvents as the plastic construction is easily damaged by some of them. I would have been scared even putting laquer thinner thru it.....
I would look for some alcohol rather than something harder. The other thing i would be to do would be to replace the nozzle completely, as even the best cleaning fails to get these little dudes completely clean and free of obstruction.
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Old 03-15-2008, 11:41 AM
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Grim Jim Grim Jim is offline
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Thanks for that, Mic. I'm always wary of what solvents will do to the plastic body of the Aztek. It's supposed to be impervious to pretty much any kind of solvent, but I've always taken that with a grain of salt.
Because I have only just read your post, I have already tried to clean the airbrush. I bought some airbrush cleaner from the LHS and I left it to soak for a couple of hours. It did get quite a bit of dried paint out of it, and the inside of the airbrush body looks much cleaner now, so perhaps it will work better now.

The nozzle is actually brand new, so I don't think that's where the problem lies. But I agree that it's very hard to get them really clean. I have been told that they can be dismantled without destroying them, but the only time I tried, on an old, knackered one, it was never quite the same afterward.

Anyway, I am soaking the nozzle now, and tomorrow, I will get everything set back up and see if it's any better. If not, I shall cut my losses and get a new airbrush. I'll let you know how I get on. No doubt you won't be able to sleep in the meantime
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