OK.  I admit it.  I’m guilty of doing some of this.  But I don’t recommend it unless you’re willing to buy replacements for the parts you mess up.  My excuse is that, as I stated on my first page, I love to tinker with things.  And, after reading about claims of improvement made by some people, I just had to try it.

Tuning, if you’re not familiar with the term, means making modifications or adjustments to improve performance.  In the case of an airbrush, this can include polishing the needle and changing springs.

Polishing the needle is the most common tune, and it can actually make some difference.  The new Renegade series of brushes from Badger advertise a polished needle, and this may contribute to the glowing reviews I’ve read.  Some people who airbrush for a living polish their needles, even with expensive brushes.  But many, maybe even most, don’t.  Theoretically, roughness on the tapered part of the needle can cause droplets to fly off before reaching the tip and result in unwanted overspray.

You can find a variety of instructions on the web for needle polishing, some involving tools like Dremel motors, hand drills and fine sandpaper.  I have a very fine Arkansas stone, and I stroked the needle gently on it while rotating it and trying to maintain the right angle.  I checked my progress frequently with a 25-power microscope.  When I saw that the machining marks were gone, I switched to a leather strop charged with cerium oxide polishing powder.  Then I finished off with liquid polishing compound on a paper towel. I did end up with a very pretty needle.

Did it help?  Well, at least it didn’t hurt.  It may have given me a tighter pattern but I would say it is insignificant for painting models.  The risk here is that if you change the taper of the needle, you might get a pattern you don’t want.  And, if you cause the needle to be out of round where it mates with the nozzle, it may not seal off the paint completely when you release the trigger, and it could even lead to nozzle damage.

Some have advised matching the nozzle to the needle by working them together with polishing compound, like you might do to seat valves in an engine.  I don't think this is a good idea.  In the first place, I don’t believe it will do any good.  I can’t see where what goes on inside the nozzle can have any effect on spray pattern.  Secondly, the wall of the nozzle is already very thin and easy to damage.  Any honing can only make it more fragile.

The other thing I’ve tried is messing with the air valve spring tension.  Being kind of lazy, I thought it would be nice not to have to press as hard to get air.  So I dismantled the air valve, being careful not to lose the tiny parts, and took out the spring.  Then I took apart some old ballpoint pens and found a spring that was pretty much like the original.  I carefully saved the original in case I needed to backtrack.  With a little stretching and trimming I was able to make the new spring so it was barely strong enough to shut off the air when the trigger is released.  Was it worth it?  Well, I like the feel, but I don’t think it will help the quality of my work at all.

In the end, if it had a significant effect for the average user, wouldn’t the manufacturers do it?  They certainly know what makes an airbrush tick better than you or I.


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