Now what am I doing wrong?!

Gern · Apr 10, 2016

I tried to do some airbrushing earlier today but didn't get very far. First my brush would not spray paint at all even though it would spray thinners. After a good strip down and clean with cellulose thinners - including running through the nozzle with fine fuse wire - I managed to get paint (Tamiya acrylics thinned 50/50 with XF20A) to spray except that it kept spitting and spluttering. I cleaned up again and now my brush is spitting and spluttering even while spraying water or neat cleaner. I've also noticed that the spray stream waves around from side to side even while I hold the brush perfectly still.

The only thing I can think of is that I've somehow damaged the needle or nozzle but I can't see any signs of damage under a magnifying glass.

Any suggestions anyone?

stona · Apr 10, 2016

There are only really two aspects that can go wrong, the fluid and the air. You said initially the brush wouldn't spray any fluid but now it does, badly. That, and your description of an inconsistent spray pattern do point to a fluid problem. I would double check the paint way (from cup to nozzle) and obviously the nozzle and tip themselves.

As far as the air goes, assuming this is an internal mix brush, there is also an airway to the tip. If you just demand air does it pulse in any way? Check that the nozzle cap is sealing to the airbrush. If you demand air and then introduce fluid is there any pulsing? If you remove the nozzle cap there will be a hole (or holes) behind the nozzle. Check that they are not blocked in any way. You can push a piece of fine wire into the hole(s) carefully to clear them.

I have to say, on what you've said so far, this sounds more like a nozzle or paint way problem than an air problem.

Cheers

Steve

Fenlander · Apr 10, 2016

Check the needle tip as well Dave. If slightly bent, it can cause the spray to go off centre and spit like hell. Not sure if it could cause a fluctuating flow though.

Gern · Apr 10, 2016

Hi Steve.

I cleaned out the airway with a small brush when the problem first appeared - I got lots of dust but it's clear now. With an empty paint cup, I get a good, steady flow of air with no pulsing when I press the trigger for just air and when I also pull back for paint.

I've just checked there are no leaks on the air cap by holding it underwater and spraying - very gently! The only air that comes out is coming out of the nozzle at the front.

As for the paintway to the nozzle, I've dismantled and cleaned it thoroughly with meths, A/B cleaners and cellulose thinners. If there is anything stuck down there, I don't know how to get rid of it if those don't work.

yak face · Apr 10, 2016

To me it sounds like a partially blocked nozzle dave, i would try soaking the nozzle in cellulose thinners ( removing the tiny rubber o ring first if its got one) and cleaning it out by poking something like very fine fuse wire through it . Ive had similar problems in the past and found it was dried paint inside the nozzle hope this helps tony

Gern · Apr 10, 2016

Hi Graham. I couldn't see any bends or damage to the needle tip, so I tried it in another A/B and it works fine with no spluttering. I tried the needle from this other brush in the problem A/B and got the same spluttering so I think I've eliminated the needle itself as the source of the problem.

I don't know what it is with me and fluid systems! I had a new bathroom fitted on Friday. All working fine except I'm waiting for them to re-fit my shower - at least that's what I thought. I turned the water heater on this afternoon and my central heating won't stop pumping hot water through the radiators - even though it's turned off and the temperature is waaaayyyyy above the thermostat setting. But of course I've got no hot water! I'm off to boil up some saucepans of water for a bath - I may be some time!

Gern · Apr 10, 2016

Hi Tony. That was my first thought - I've got some dried paint somewhere. I soaked the nozzle and the cap in cellulose thinners for a couple of hours this afternoon and I've run through some thin wire. I've held both up to a light and they look clear and circular.

stona · Apr 10, 2016

It's difficult without having the brush in front of me, but it doesn't seem to be an air problem. Try this. With the nozzle under magnification push the needle gently into it. If your nozzle is split this should be easy to see as the needle moves forward. I suggest this because a split is not always easy to see, even under magnification, unless it is being eased apart, as it will be by the needle. Also, as the split in the nozzle opens the needle will advance further than it normally should.

I had exactly this problem myself on one of my Iwatas a while ago. I probably split the nozzle myself by over enthusiastic re-seating of the needle. I didn't get exactly your symptoms, but I did get an odd spray pattern and a different feel to the control of the paint (because the needle was not seating in its normal position).

Cheers

Steve

Gern · Apr 10, 2016

I've had a go as you suggested Steve - in between boiling up saucepans of water. I've pushed the needle much more firmly into the nozzle than I normally do and can't see any sign of a split. I don't want to try any harder just in case I accidentally split it.

Fenlander · Apr 10, 2016

Which airbrush is this Dave?

Gern · Apr 10, 2016

It's my cheapo HD-470 with a 0.3mm nozzle. I got this in between buying the H&S Ultra which I'm still iffy about with it's removeable cup and the one that you reviewed for John.

Fenlander · Apr 10, 2016

You say you have tried another needle in it. Is it possible to swap the nozzle too, just to eliminate it from the equation?

What happens if you spray paint without a needle installed?

Gern · Apr 10, 2016

\ said:
You say you have tried another needle in it. Is it possible to swap the nozzle too, just to eliminate it from the equation?
What happens if you spray paint without a needle installed?

You da man! The nozzle has split around the screw threads at the back - which is why I didn't spot it earlier. All I gotta do now is find a supplier for a replacement.

Thanks guys.

PS Graham - I dread to think how much mess I could make trying to spray without a needle!

Gern · Apr 11, 2016

Sorted! When I bought that Fenghua brush from John, I bought a 0.4mm needle/nozzle set as well to replace the 0.3 set that comes with the brush. The 0.3 set fits just fine in my spare brush. I only use it for Klear so it will be OK for that.

Fenlander · Apr 11, 2016

\ said:
Sorted! When I bought that Fenghua brush from John, I bought a 0.4mm needle/nozzle set as well to replace the 0.3 set that comes with the brush. The 0.3 set fits just fine in my spare brush. I only use it for Klear so it will be OK for that.

Great stuff Dave, all a matter of elimination. I often take the needle out and spray cleaner through the open nozzle. It is only the same as spraying with the the needle full back plus a bit

stona · Apr 11, 2016

I'm glad you've got it sorted Dave. These things can be very frustrating. A nozzle failing or splitting in that area is not something I've seen before (and is obviously difficult to see in any case!). We all live and learn.

Cheers

Steve

stona · Apr 11, 2016

\ said:
I often take the needle out and spray cleaner through the open nozzle. It is only the same as spraying with the the needle full back plus a bit

Me too, every time I flush a brush I remove the needle so that I can wipe the bottom of the paint cup and then spray a little thinners through the open nozzle as I replace the needle.

You can only do this if you are prepared to remove and replace the needle from the back, something I've always done, despite dire and pointless warnings by some not to do so :smiling3:

Cheers

Steve

dubster72 · Apr 11, 2016

\ said:
Great stuff Dave, all a matter of elimination. I often take the needle out and spray cleaner through the open nozzle. It is only the same as spraying with the the needle full back plus a bit

Me too, although I generally just draw the needle clear of the paint cup. Like Steve says, it makes wiping the cup easier.

Steve Brodie · Apr 11, 2016

A bit pointless as its now fixed, but i was going with nozzle, i tried cleaning mine with a reamer and couldnt understand why no paint was coming through, needle pushed through all ok - until i took it along to SMW 2015 and the good guys at Airbrush heaven spotted - a) needle was bent and b) i had opened up the nozzle so when pulling the needle back it was still blocking the tip!!. Fantastic things when they work but nightmares when they dont. I liken it to playing golf, you can hit a perfect ball, set back up again and whump, sideways into a bush - but you have done nothing different !!!!, stupid game i gave up !

Stevekir · Apr 11, 2016

Came late to this. When I had huge blockages some time ago (not your eventually discovered problem) I am pretty sure the cause was lumps of paint in the paint bottle (Vallejo Model Air) which I eventually saw making their way in to the cup. I now pour the paint into a small gutter (curved styrene sheet) to catch the blighters when they make their way down.

Now what am I doing wrong?!

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