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Irregular airbrush paint flow

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  • Member since
    February, 2019
Irregular airbrush paint flow
Posted by JackieK on Saturday, May 04, 2019 2:05 PM

Hey guys

I've run across this problem with two airbrushes I recently purchased, with one being H&S Ultra and the other a cheap Iwata knock off.

It's worth noting that I've managed to get several successful painting sessions with the both of them and the whole issue starts without an obvious reason.

At some point the paint starts flowing in an irregular fashion. Basically, with even pressure applied on the button (both downwards and backwards), the paint flows as expected, but completely stops after a second or two. As I pull back or push down the button, the issue remains the same, but for the larger pattern. At times the paint randomly unclogs itself and starts flowing the way I'm used to, but stops shortly after. It almost feels as if the paint accumulated in the nozzle and blocked itself, but there's really not enough time for it to dry as it sometimes happens in the beginning of a session. I don't take long pauses either. The airbrush doesn't "spit" dry blobs of paint when I pull the needle as far back as possible, just a large thick layer, as is to be expected. I have no control over the flow as a result and it's no way to treat a model.

This whole unclogging bit naturally made me think I did a lousy job of cleaning the airbrush in the first place, but I regularly put in the effort to clean the nozzle, the body and the cap with dedicated cleaners. The needle is definitely straight and well-polished and I always push it out from the front. I'm thinking the compressor is not at fault either, since I painted several layers with it without any problems whatsoever. I initially thought I somehow damaged the nozzle in the "Iwata", but this surely isn't the case here.

I use Vallejo/MIG/AK with dedicated thinners.

Being somewhat new in airbrushing I feel like I'm missing something and would appreciate any suggestions.

Tags: Airbrush , flow , Painting
  • Member since
    February, 2019
Posted by JackieK on Monday, May 06, 2019 2:28 PM

This reddit post shows the exact issue I'm experiencing. The discussion there made me think it might be a paint problem, since spraying thinner or alcohol by itself goes without problems.

I use Vallejo Airbrush Thinner for Vallejo Air and MIG/AK paints, since they passed the eye test and I figured they work together just fine, but now I'm starting to have second thoughts.

I've been considering buying either the Airbrush Flow Improver from Vallejo, dedicated AK/MIG thinners or just straight up switching to Tamiya/Gunze. Has anybody experienced this?

  • Member since
    November, 2018
Posted by oldermodelguy on Monday, May 06, 2019 4:44 PM

If it starts out spraying fine then screws up a ways into the paint job, I'd suspect tip dry. It's a good idea to do a couple of things. Either put some retarder or flow aid into your paint blends, thus avoiding tip dry for the most part. Then keep a paint brush or Qtip handy with a cap full of thinner near where you are spraying. Then when this occurs dip the brush or Qtip in the thinner and just wash off the end of the airbrush with the needle protruding out a bit.

If it starts right off painting screwy and assuming a clean airbrush, I'd then suspect the paint is not thinned enough and or the air pressure not set quite high enough.

  • Member since
    May, 2013
  • From: Indiana, USA
Posted by Greg on Tuesday, May 07, 2019 9:18 AM

What ranges of PSI are you using? I don't have much experience with AK or MIG but I might be able to help with Vallejo. What you describe does sound like dry tip, but I'm not so sure the same thing should be happening with the AK or Mig.

-Greg

  • Member since
    February, 2019
Posted by JackieK on Tuesday, May 07, 2019 2:00 PM
Thanks for the suggestions, I'll try the Vallejo flow improver as soon as I can. The brush also sounds like a great idea. I usually spray at around 25 PSI.
  • Member since
    May, 2013
  • From: Indiana, USA
Posted by Greg on Tuesday, May 07, 2019 7:48 PM

JackieK
Thanks for the suggestions, I'll try the Vallejo flow improver as soon as I can. The brush also sounds like a great idea. I usually spray at around 25 PSI.
 

25 PSI should be ok for Vallejo. They recommend 20-25, I use 22 or so, you use 25 so we are both inside recommended range.

Sounds like good advice from OMG re is your paint thinned enough, and dry tip. Glad to hear your are getting some Vallejo Flow Improver. You should find the improvement to be night and day.

-Greg

  • Member since
    November, 2018
Posted by oldermodelguy on Wednesday, May 08, 2019 6:59 AM

JackieK
Thanks for the suggestions, I'll try the Vallejo flow improver as soon as I can. The brush also sounds like a great idea. I usually spray at around 25 PSI.
 

I set my gauge @24-25 psi for MA, then after the drop when I hit the trigger I get 22-23psi working pressure with a siphon AB and side cup attached. That seems to work fine for me with VMA. But thats a siphon brush not gravity brush just fwiw.

  • Member since
    May, 2013
  • From: From the Mit, but live in Mason, O high ho
Posted by hogfanfs on Wednesday, May 08, 2019 7:08 AM

Greg

 

 
JackieK
Thanks for the suggestions, I'll try the Vallejo flow improver as soon as I can. The brush also sounds like a great idea. I usually spray at around 25 PSI.
 

 

 

25 PSI should be ok for Vallejo. They recommend 20-25, I use 22 or so, you use 25 so we are both inside recommended range.

Sounds like good advice from OMG re is your paint thinned enough, and dry tip. Glad to hear your are getting some Vallejo Flow Improver. You should find the improvement to be night and day.

 

 

I was getting dry tip with Vallejo too, and the flow improver did make a huge difference. And now from this experience, any new acrylic paint I purchase, I make sure to purchase their brand retarder or flow improver. Just to be on the safe side. 

 

 Bruce

 

 On the bench:  1/48 Eduard MiG-21MF

                        1/35 Takom Merkava Mk.I

 

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