Airbrush question.

[mikeyb2]

Well my airbrush arrived but unfortunately without it's compressor, so I'll have to wait another few days before I can use it.
I've no experience at all with one, but I bought it to touch up the sunburst where needed and also possibly to use it to give the sunburst a shellac seal coat.
Would I need to thin the shellac any further than a 1lb cut, which I already have mixed? Or possibly raise the compressor pressure to an appropriate level?
Thanks in advance. Mike

[Richard500]

Quick, simple answers? I’ll try. First, there are many airbrush designs, principles of operation, air cap (nozzle) options etc. Versatile, controllable models are used by artists, plain atomizers are the hobby level and inexpensive ones. But there are some basics:
1. Highly-thinned (low viscosity) paints. Much thinner than would be used in a larger spray gun. If the gun doesn’t have one, make or buy a small cup with a hole in the bottom: this is your viscosimeter. Once you get a good workable recipe, the cup will tell you (seconds to drain) that you’re thinned properly.
2. Know your tool. Clear a workspace, take the assembly diagram and take the gun apart several times. Because you will have to do this every time you forget to flush it after use, or make a mixing mistake, or fail to filter your paint. Many small parts! Do this early.
3. Filter, filter, filter. All spray tools have tiny orifices, sliding needles, and are easily gummed up or clogged. Even a big automotive gun needs 100 micron filtration.
4. Pressure. Yes, it’s a control parameter, but the little (diaphragm) continuously running (no tank) compressors usually supplied are limited, around 35psi, which is not much, and may not even have a usable regulator, since there’s really no tank.
5. First runs: start with spraying plain solvent. Two reasons. The gun needs cleanup even when new, and the low viscosity solvent stands the best chance of actually spraying. Test the control or controls on the gun to see how much comes out, how it’s distributed and whether there are ‘spits’ and drips.
6. Then, start mixing pigments, tints, whatever, cautiously. Take notes, spray lots of test pieces, even cardboard. Since the airbrush often only holds a few cc of material, for consistency, mix up a larger amount in a small jar. Use a syringe or eyedropper.
7. After each use, especially with something that dries very quickly, like shellac, run the solvent or thinner for that material through the gun to clean it.
—all this sounds like finicky work, and it is, multiplied by having different materials to shoot. Each material is a different story about atomization, drips, runs, thinning.
For something that has to be thick (like protective coats) an airbrush may not be the most sensible solution compared with a pad or brush.

[mikeyb2]

Richard, I take your point about understanding the airbrush and practising etc. and everything else you pointed out, but with regard to your last sentence, the shellac coat is only to prevent the waterbased stains used for the sunburst from smearing, prior to clear coating. I've seen many references to airbrush use for this purpose, as a pad or brush is more likely to disturb the burst, so the airbrush is the most sensible for this purpose. It seems common practice according to what I've read.
thanks Mike

[sounds_good]

Richard, thank you for the detailed tutorial. I do not have an airbrush,
but I can visualize the steps you describe. If ever I think maybe I
should purchase an airbrush, I will come back here first and re-read
your post.


Thanks,
sounds_good