Strange issue with new AB, could use some help

I have to apologize for the latter half of the text being hyperlinked...I tried to edit it, but it didn't work. 

It just occurred to me to mention what paint was already on the work when I had the above problem.

The first time it happened with this airbrush, it was spraying Tamiya flat red acrylic over cured Tamiya TS-17. The next time was a custom mix of thinned Tamiya acrylic greens for the green nose of the P-51 I'm now doing. The time after that was today, spraying straight Future over decanted Tamiya AS-12 Bare Metal Silver. 

TF

Hi mrmike, thank you for your reply.

After work tomorrow I will pull the needle and do as you suggested. Provided it checks out, I'll reassemble the AB, crank up the pressure and do a test. If the needle has a burr or is out of true, I will install the other needle it came with and do a test. 

Thanks again, and I will let you know what I find.

TF

It may be your air pressure.  I have a brochure from Paasche on the H that says:

20 lbs or less: Stipple and granulated effects, pressure will vary with viscosity of fluid.

20 to30 lbs: Medium consistency water colors, inks and dyes.

30 lbs or more: Heavy fluids, acrylics, reduced lacquers, varnishes, paints or ceramic glaze.

It looks to me like you are getting stippling.  Older versions of the H had a trigger limiter to cause this on purpose.  Artists use it to get texture.  You might want to see how it sprays something thin like ink or food colors.

Don

Hi Don,

Thanks for your reply! I will try to crank up the pressure and see if that helps. It seems to me that the last time tried to get more pressure out of my little Badger compressor that it would not go much higher but I'll give it a whirl. 

Incidentally, it is common or normal that an airpressure gauge will read at one point while not spraying, then drop a few psi when spraying? It rather makes sense to me that it would, but when talking about the above pressures you listed, would I be correct in guessing that the pressures you listed are what would be observed while the trigger is pressed? It might seem like a silly question, but for most of the 20 years or so I've airbrushed, I never had a gauge/regulator, and I only started using it less than a year ago. If the pressure seemed too high, I'd simply loosen the hose connection at the compressor to cause a leak, and use a small piece of tape to hold the connector at the right spot. A bit of a craptacular solution, but it worked.

I don't have any food colouring at home at the moment, but I accidentally bought a double of a Tamiya acrylic colour recently so I'll mix up a very thin batch of that and test on some scrap...something, lol.

Thanks again,

TF

It is normal for the pressure to drop a little when the trigger is depressed.  It doesn't matter as long as you're getting enough air to get good atomization.  If you are, whatever the gauge says is pretty much beside the point.  Nothing wrong with the way you were doing it. That's essentially how pressure is controlled with the Iwata SmartJet compressor, an adjustable bleed.  I believe Paasche's intent is that the pressures recommended are with the trigger depressed.

Try spraying your thin paint on some paper towels.  You'll be able to tell if it's atomizing OK.

Don

Mrmike and Don,

Thank you both for your help. Using both of your tips, I was able to solve my problem tonight! Rather than do one thing at a time to see which solution did the trick, I "threw the book at it" because, to be completely honest, my patience was beginning to wear thin and I really want to progress on my current project!

Mrmike, the first thing I did was disassemble the H and check the needle. I could see no issue with the tip with the unaided eye, but under a magnifying glass, the tip appeared to be juuuust slightly flattened, and when running it lightly along by finger, sure enough, I felt a burr. I thought I read somewhere about using an emery cloth to polish out a burr on a needle, so lacking an emery cloth, I used some Testors sanding films, the finest two grits, and that sorted the needle. 

As far as the air pressure goes, I turned on the compressor and reefed on the adjuster until the pressure went up, and it maxed at just under 50 psi. That seemed like it would be WAAY to strong, so I dialed it back until with the trigger pressed the gauge read about 25 psi before performing a test.

I mixed up the paint, Tamiya X-5 Green, with some X-20A thinner and filled the paint cup. The picture below is the first spoon I sprayed (I found a few plastic spoons). The atomization seemed quite good, but I needed to play a bit with the paint adjuster and distance to the work.

The picture below is the last of four spoons I sprayed, the preceding two getting a bit better than the first. The last spoon really got a wet coat quickly, so I dialed back the paint adjuster and continued. After a few coats, a few minutes between coats, this is my result. 

The picture below was an extra experiment since I had extra paint. I sprayed the side of an empty tissue box, and tried to do a gradient. It worked really well, being nice and even and gradually darkening from box edge to the center, but I had so much extra paint I just kept spraying, darkening toward the center. You can see that the atomization toward the box center is actually rather good, being fine and even. I'm quite happy with the result.

Don and mrmike, thank you both very much for your help! I really appreciate it very much. You guys helped preserve my sanity! 

That's great to hear that you got it figured out.  Thanks for getting back to us with the solution.  Maybe it will help someone else with a similar problem.

The H is a very capable airbrush.

Don