I found a Sata Minijet 4 for a reasonable price and these were Allen's comments.
The tip on the gun was designated as an SR (spot repair) and I didn't know whether it would be suitable for instrument finishing.Allen -
The price of the gun is really good. I would grab it no matter what.
I don't know if its going to spray the shellac well or not for you. There are heaps of variables in gun set up and spraying style as well as air pressure.
The gun is designed to spray automotive paint, and it would be thinned to the same consistency as what you are using. Perhaps even a bit thicker, and it does that brilliantly.
All a spray gun is designed to do is atomize paint into small particles that aren't too large (heavy looking surface) and not to small either (dries before it reaches the surface). You can vary the way a gun does this by several ways.
1. Air pressure, lower has less atomization. Do this if product is too thin. Higher if too thick.Small adjustments can make big differences.
2. Fluid tip and air cap. Larger for thicker material, smaller for thinner.
3. Fluid needle adjustment. In for thick material (less has to be atomized) out for thin (more can be atomized).
4. Thin the paint more or less to bring it into line with your equipment and spraying style.
5. Spraying distance and speed.This is probably the biggest one. No matter how well a gun is designed and set up this will make or break the finish that you get. Takes a bit of practice, but you adjust this by looking at the wet edge you are spraying and observe how the finish is laying down. I would get my apprentices to fill their gun with water and practice laying a nice even wet coat on an old bonnet. They think that it is too easy until they try it.
So I guess I need to know what those knobs actually do Allen.Allen -
The gun is designed as a spot repair gun for the automotive trade. It's the small size. No good at all for spraying a complete Landcruiser.
We would use a gun this size for doing door jams, fender skirts etc. Anywhere that we would only want to make up a small amount of paint and have the convenience of a small gun.
It should be good for guitars. You want the pot to be able to hold enough product to get one coat on the intended surfaces. It's not necessary to have enough for 3 coats, 'cause your going to let the surface flash off an appropriate amount of time before you spray some more.
Gives you time to refill and let you have a little break.
The tip should be fine to use on a guitar. You aren't trying to paint anything huge here. The rest would be controlled by air pressure, solvent, spray technique etc. The fluid nozzle, tip and air cap will be sold as a unit, it you were wanting to change them, and they will be pretty expensive. Essentially they are the spray gun, the rest is there just to make those pieces work.
I'd be glad to give anyone pointers on spraying. It's a lot easier when I've got them right beside me, but I should be able to clear a few things up. Most people haven't got a clue as to what all the knobs are for on the gun, and just knowing what they do makes a huge difference in your ability to trouble shoot spray problems.
I've just searched every thread on the OLF for this type of information but Allen has nailed it all in a couple of PM's.
So, I owe him lots of beer.
I'm sure a few other people will have some questions too.