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I'm a new airbrush user with my first generic brand airbrush for practicing with before I commit to a more expensive model.

Recently my airbrush has started making a spluttering sound when I apply more air pressure. The paint is coming out unevenly. The paint is coming out as a very thin mist with lots of large droplets.

I'm using Vallejo acrylic paint, and Vallejo thinner.

I can't even put down a smooth base coat any more.

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    Have you disassembled and cleaned your airbrush. Dried paint on the needle and/or the nozzle can disrupt the vacuum effect which draws paint into the airstream. I clean my brush after every session. Aug 30 at 17:37
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    If the brush is clean, consider your paint to thinner ratio. Thinner doesn't just make the paint lighter so that the airstream can grab it and so it can get through the gun, it also breaks down the paint's tendency to clump together. You can't just skimp on the thinner and compensate by increasing the air pressure. If you do, you get large droplets. Aug 30 at 17:53
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Good advice from Henry Taylor in the comments. A clean nozzle and proper thinning are two key things. Another is various problems with air in the wrong amounts and the wrong places.

Why Your Spray Gun is Spitting is a good article on the common problems and fixes. Some of the components mentioned may not apply to your airbrush, but I'll paste the essential portion (bulk of the article), here in case the link dies:

  1. Fluid Nozzle – The first area to check if your spray gun is spitting is the fluid nozzle. A loose fluid nozzle does not properly seat in the tip of the spray gun and causes air to enter the fluid supply resulting in spitting. To solve this issue properly tighten your fluid nozzle or if unable to tighten the fluid nozzle inspect the head of the spray gun to see if there is any stripping of the fluid seat or the fluid nozzle threading is stripped.

  2. Air Cap Properly Matched – If you are using a siphon/suction-fed spray gun, the correct air Cap is vital to being able to properly spray and not experience spitting. With a suction fed spray gun you have to use a suction/ siphon fed spray gun air cap and NOT A PRESSURE FED AIR CAP. Siphon-fed air caps cause air to be drawn across the material allowing it to be supplied and sprayed; a pressure cap will not create a suction effect, resulting in fluid not being supplied to the spray gun.

  3. Packings - If you have the correct air cap and fluid nozzle, it might be that your packing nut is bad or the physical packings are worn. Inspect the packing nut to ensure it is tight as well as the packings to ensure they are not worn or missing. If the packings are missing, make sure to order new packings.

  4. Fluid Connections- If you are using a pressure-fed spray gun, make sure your fluid connection is tightly applied to your spray gun.

  5. Gravity or Suction Cup – If you are using a gravity or suction-fed spray gun, make sure your cup is seating tightly into the spray gun. Inspect the threads of the cup to ensure they are not stripped as well as inspect the threads of your spray gun to ensure they are in good shape and not stripped. If either are stripped replace the cup or gun body if necessary (or buy a new spray gun).

  6. Material is to Heavy/Viscous – If you're using a suction-fed spray gun, your coating may be too viscous to be sprayed with a suction-fed spray gun. If you want to use a suction-fed spray gun to spray the material, you can try increasing the fluid nozzle and/or selecting a higher CFM air cap (which will allow for better draw of the material up to the fluid nozzle).

  7. Air Cap Clogged (Suction Spray Gun) – Check your air cap to ensure that is not blocked by any paint. If it is, clean it out using a cup of proper cleaner.

  8. Fluid Pressure too Low – If you're using a pressure-fed spray gun, you may not be applying enough pressure to your coating to supply the gun appropriately. This often happens with very thin material like stains that you are trying to keep coating to a small amount. To remedy this, try applying a little more pressure to the coating and then using your fluid adjustment knob to restrict fluid to the spray gun.

  9. Fluid Passage Clogged – Clean the fluid passage of your spray gun with an appropriate cleaner to ensure no particle has become lodged in the spray gun due to sitting for a while or a partial hardening of material. If this is a recurring issue consider adding a fluid filter to your pressure pot or straining your material prior to spraying appropriately.

Note: This quotation has been corrected for spelling, punctuation, and capitalization to improve readability.

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  • Everything was OK at first, then I changed colors. I rinsed the brush out with water, then airbrush cleaner, then flushed with water again. Then I dried it and left it to settle. After that, it went wrong. Aug 31 at 8:22
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    Then I dried it and left it to settle After each session you should disassemble the Airbrush, take the needle out and clean the needle and nozzle properly with an old brush, cleaner and some paper towels. Between colors you can fill some water in your airbrush, "pinch" the nozzle with your thumb and index and then slowly letting some air out. This will flush out most of the pigments that way.
    – Lapskaus
    Sep 1 at 13:49

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