Since there is so much controversy regarding how to maintain the airbrush, I'll share some of my thoughts and procedures about how I keep my airbrush functioning without blockage while never having to disassemble it.
The first rule that one must adopt is a simple one and relates to the laws of physics. Virtually all airbrush paint requires air to dry and goes through phases, including evaporation and curing.
Evaporation Phase
Paint contains a type of solvent which gives it a liquid form so that it can be applied. Once you apply the paint, the exposure to the air allows the solvent to evaporate, which we call "drying." The speed at which paint dries is affected by environmental conditions, such as humidity, air movement, and temperature. With some airbrush paints, drying can happen almost instantaneously.
The Curing Phase
In addition to the solvent evaporating, a chemical reaction in the paint occurs through oxidation and/or coalescence. The molecules of the paint form bonds through crosslinking to attach to the surface and each other. This is a slower process than evaporation, and the characteristics of the paint may change as curing progresses.
Air in the paint bottle
If air dries the paint, then why doesn't paint become solid from the air in the paint bottle? During the evaporation process, solvent leaves the paint, but airborne solvent may also re-enter the paint. If the concentration of solvent in the air is high enough, there will be as much solvent re-entering the paint as is leaving the paint.
In open air, the solvent is carried away, leaving more room in the air for the solvent to evaporate. In a closed environment, such as a paint bottle, the solvent leaving the paint builds up until the concentration is high enough that the solvent leaving the paint matches the amount of solvent re-entering the paint from the air, and reaches a state of stable equilibrium. Without the ability for the paint to have a net loss of solvent, the paint cannot reach a solid state.
However, if there is enough air in the bottle to hold the solvent, it may allow enough solvent to escape the paint in order for the paint to become solid.
Paint in the airbrush
A similar model is found when paint is inside the airbrush body. A small amount of air will not allow the paint to dry. However, if there is enough air in the body of the airbrush, it will allow small residual bits of paint to harden and dry inside it.
Prevention
While it seems obvious that to avoid paint drying and clogging the airbrush, it is simply a matter of preventing air from entering the airbrush body. However, the habit of spraying all the paint out of the airbrush before parking it, creates a scenario for paint to dry inside the airbrush, because this method replaces the paint in the airbrush with air, leaving small amounts of residual paint to interact with the air.
No air inside the body of this airbrush.
Air inside the body of this airbrush is in contact with residual paint and will dry and harden.
When this paint dries inside the airbrush, it becomes harder, and it compromises the performance of the airbrush and may prevent it from spraying at all.
Problem Solved
If the amount of air entering the airbrush can be minimized, then the user will not have to suffer these problems.
The good news is that it is easy to prevent air from entering the airbrush, by simply leaving the paint in the airbrush.
Many fear that paint remaining in the airbrush will dry and harden, but one must keep in mind that contact with open air is required for paint to dry. By leaving the paint in the airbrush, there is no exposure except for the surface of the paint in the cup, and that can be managed by covering the cup to prevent air movement, or adding water to the cup. The closed system functions just like a lid on the paint bottle.
Those who use a side cup airbrush have an even greater advantage, since the paint tube to the airbrush body is long and narrow, air has little chance of entering the airbrush.
If you still harbor fears about leaving paint inside the airbrush, simply replace it with water. However, make sure that you don't spray all the water out. Leave water inside the body of the airbrush, and any residual paint inside, will remain in a liquid state forever, just like it does in the paint bottle.
What about cleaning?
Using this method, I've been able to use and work with my airbrush for over a year now without disassembly and have experienced no clogs. The only time I need to clean my airbrush is when I'm changing from a dark transparent color to a light opaque color or white. Then I'm only flushing it out thoroughly with water, Windex with ammonia, or white paint (yes, white paint can be used as a cleaner). I haven't even removed my needle in a year!
I hope this helps reduce some of the fears associated with leaving paint in the airbrush.
