What's happening when you spray?
Let's explore the basic underlying concepts of spraying with an airbrush. Once you know what's happening and why, you'll be able to bend or even break the normal rules to create stunning effects and techniques.
"Knowledge is power"
Technical jargon warning.
An aerosol spray is a mixture of two or more liquids with a gas. The liquid gets broken up into tiny droplets, atomized. The atomized liquid is suspended in the gas, usually air.
Liquids in suspension tend to settle. It gradually falls to the floor.
End of technical jargon.
When the liquid hits the air stream the force of the moving air breaks up and atomizes the liquid into small globules (think tiny spheres but not nearly so neat and perfect as a sphere should be).
When the globule hits something it forms a dot. The height and width of the dot is determined by how much the droplet dries before impact with the surface.
- Greater air pressure = smaller dot = drier, rougher spray texture
- Lower air pressure = larger dot = wetter, smoother spray texture
Users try to spray with as little pressure as possible, but enough to actually break up the paint being sprayed.
- Thicker, chunkier paint = greater pressure to pull and atomize the paint
- Runnier, more uniform paint = less pressure to pull and atomize the paint
- Greater pressure = less paint sticking to the surface
- Less pressure = more paint sticking to the surface
But I do need to bring up one other rule here. Overspray. Overspray is the biggest health risk any painter faces. Breathe it and bad things will happen to you over time. So here's the biggest rule.
Ventilate your work area.
I'd much rather you stuck around for awhile.
The tip (apex) of this spray cone starts somewhere between the needle's tip and the nozzle's tip depending on how much liquid you're letting out at any one time.
- Less paint = cone's apex closer to the needle's tip
- More paint = cone's apex closer to the nozzle's tip
- Airbrush closer to the surface = smaller spray area
- Airbrush further from the surface = larger spray area
I should also mention that paint builds up quicker the closer you hold the airbrush to the surface. This is because you're spraying the same amount of paint in the same amount of time over a smaller or larger area, therefore...
- Airbrush closer to the surface = quick paint build up
- Airbrush further from the surface = slow paint build up
Don't spray at an angle or you'll get an off-kilter oval spray pattern. If you're trying to spray off-kilter oval-shaped spray patterns, then by all means experiment with angle, otherwise spray straight onto the surface for the circle.
Every technique any painter teaches you starts with you spraying perpendicular to the surface.
The circular dot is the basic shape that everything gets built out of while you airbrush. Here's how you do it.
Spray a quick blast of paint without moving your hand. Congratulations. You have a dot.
- Large dots = spray further from the needle's tip
- Small dots = spray closer to the needle's tip
Notice, again that it takes more time to 'cover' the larger area with paint than it does to 'cover' the smaller area. Remember...
- Spray intensity is greater the closer you are to the surface
- Spray intensity is less the further you are from the surface
Start spraying a dot and move your hand parallel to the surface. Congratulations. You've got a line.
If you did it like most beginners then you started spraying paint and then moved your hand. Notice the larger 'dot' at the beginning of the line. You spent more time there so the paint covered more.
- Start moving your hand before you start spraying and you'll eliminate this problem.
- Stop moving your hand after you stop spraying to eliminate a possible dot at the other end.
- Air On
- Paint On
- Paint Off
- Air Off
- When airbrush problems happen, then generally happen when
the air pressure changes dramatically. i.e. when you turn
your air on and off. This is the most likely time for your
airbrush to spit, or sputter. You should always...
Turn your air on and off on a test sheet to save your work from splats of paint and miss fires.
- Keeping the motions separate helps you do better work, for instance it lets you avoid dots at the beginning of your lines and dagger strokes.
To form a line, move your hand parallel to the surface of the work while spraying. But what happens when you vary the distance from your hand to the work?
You get a dagger stroke.
They take practice to get consistent. But it's worth it, especially if you want to learn how to write in script.
A line is all well and good, but what if you want something that covers more area than a small, tight, line. If you have amazing technique and excellent muscle memory (you have to do that same motion over and over just moved slightly over) you can fill in a larger 2 dimensional shape freehand and still preserve your hard edges.
For those of us who haven't penetrated the depths of airbrushing magic (or who use a spraygun) we need a mask. A mask presents a barrier between the piece being sprayed and the spray. It takes the heat in order to shield the piece below.
- The closer a mask is to the surface the more defined the edge becomes.
- The further the mask is from the surface the less defined the edge becomes.
Getting your airbrush basics down let's you move on to more advanced ideas and concepts. Most users understand what I just told you, though they probably never put their understanding into words. Master the fundamentals and everything else becomes easier. Skip your airbrush basics and you'll run into hardships later.