Air Gun Protocol

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This is about a high volume, low pressure, air-powered spray gun - like the Purple Classic by Harbor Freight.

Basic Procedures

  • Let people know they are painting so they bring old clothes
  • Rags should be available - so gun is cleaned from spills readily.
  • Gun holder jig should be available for hanging gun for refills, with hose attached. Holder holds gun so strainer cup can be placed above cup.
  • Strain directly into cups, using a ladle of some sort. For 5 gal buckets, ladle can be hung on side of bucket. For 1 gal paint, ladle can be left submerged. Put lid on partially to limit evaporation in both cases.
  • Use 20 oz paint cups for longer spraying duration between refills


  • Start at 80 PSI on regulator - it should be 40-60 PSI during operation, not when idle. Look at regulator.
  • Use an air/dirt filter
  • Air filter clean-out should be pointing down, by gravity
  • Turn air on all way at bottom of handle- and use regulator to set pressure
  • Use air pattern control to get spray wider or narrower - observe and practice with water.
  • Practice spray pattern with water onto a visible surface, such as stone, cardboard, fabric
  • Hang five for distance from work piece, hang five for spray width
  • Always keep gun direction at a normal to the surface sprayed. This means 2 dimensions.
  • If sheet is on floor, normal is impossible - the only way you can do it is if angle of substrate is near 45 degrees when working on panel material
  • Long material can be hung on a wall with blocks - if using a temp structure
  • Elevate panel on floor jacks as another option.


  • If you take a break of any lenght longer than 2-5 minutes - take off cup, take off air hose, leave gun suberged up to handle in about 6" of water immediately - for water-based paints.
    • This can be done in less than a minute
  • Wipe gun with rags, so paint doesn't harden
  • For oil paints - if you're taking a break - do a diesel or mineral spirits blow-out - this also takes less than a minute


After finishing the day, this is what will make your gun last for years without clogging -

  1. Take off cup, clean it in water or solvent with a brush.
  2. Take out needle, being careful about the jumpy spring when screw thread runs out - and submerge in cleaner (water or diesel)
  3. Take off nozzle
  4. Take off subnozzle with 17 mm thin wrench - the first time taking this off you may need to put the gun in a vise
  5. Now you have the back, front, and top of gun accessible for cleaning with the small brush and cleaner. All remaining paint in feed, outlet, and back should be cleaned.
  6. For the subnozzle - may need to poke center hole with 0.035 wire if center hole is clogged.
  7. Brush the nozzle and subnozzle and needle to get all junk off.
  8. Look through subnozzle - oberve light through center hole, and all radial holes. If light is not coming through - needle out the holes. The subnozzle appears to be steel - and smooth welding wire works great for center hole. Steel is not as susceptible to damage as is the outer nozzle.
  9. Look through nozzle - observe light through mid hole and tiny radial holes - make sure all holes are clear. Torch tip cleaner needles may be required if brushing is insufficient. But that can damage the brass nozzle - so torch tip needles are the last resort.
  10. Summary: 3 apertures cleaned, all light holes shine light in nozzle + subnozzle - and you are done.
  11. Final step - run diesel through the gun, which keeps the innards lubricated. Don't use water if you're using latex paint. Just do diesel.