AIR BRUSH PAINT RECEPTACLES
Now that we’ve covered the basic types of air brushes, we need to look at a method of making the paint available for the use by the air brush. The two most common methods are via an under hung bottle or a cup. The cup may be under hung, side slung, or over head for gravity feed.
To begin with, why use a cup or a bottle? The bottle is used where large areas of the same colour are to be painted. Obviously because of their size, bottles carry a relatively large amount of paint. This allows you to cover a large area with one coat, or a smaller area with multiple coats, without refilling the bottle. Also, these areas can be covered more quickly than with a gravity feed cup.
The down side for a bottle, in some applications, is the size. If you are only doing a small amount of a single colour, or using that colour sparingly, the bottle may be too much for your needs. This is the case when doing art graphics with an airbrush. Artists painting pictures with an air brush aren’t going to use the same quantity of the same colour as, say, someone painting the hull of a large vessel. For the vessel, the large bottle works well whereas the cup would rapidly need refilling just as you are getting into the swing of the painting (no pun intended). One thing to keep in mind with the bottle, it has a small hole in its lid (something around .060” dia). Ensure this hole is open and clear. Failure to do so will mean erratic paint application as the air brush will draw a vacuum on the jar preventing paint rising to the brush. Obviously open cup arrangements don’t have this problem.
Another difference not often considered is the mass weight of the paint receptacle on the air brush. The bottle filled with paint imparts a weight mass to the brush that can be somewhat awkward to control when painting very fine areas. A paint bottle is not the best attachment when airbrushing lines for example. One needs a steady hand with as light a unit as possible. Here the cup excels.
As well as mass, the paint bottle has the down side of being large. If you’re tying to get into a small area there is obviously a restriction with the paint bottle. That being the paint bottle can get in the way when trying to get the air brush into a tight spot.
An upside to the paint bottle, as well as the volume of paint available, is the fact the top of the bottle is covered. Many of the paint cups on air brushes aren’t. Tip the air brush from any position but vertical and you wear your current choice of paint, or worse yet, your project does. Some cups have covers on them. I have a De Villbis that has a covered cup, however, most don’t. The bottle is much more forgiving in this area.
As I mentioned earlier, cups can be made to interchange with bottles, some cups are permanently mounted to the air brush, some are on the bottom, some on the side and some on the top so the paint gravity feeds to the air brush. What’s the difference?
BOTTOM FEED refers to airbrushes on which material enters through a siphon tube or colour cup attached to the bottom of the air brush. This type of air brush should have at least 18 PSI while spraying to operate properly.
GRAVITY FEED refers to air brushes on which material enters at the top of the airbrush through a top-mounted colour reservoir. Gravity draws the material into the air brush. This type of air brush can be operated at spray pressures as low as 8 PSI. Gravity feeds are the best for detail work. Because of the lower pressures and they are ideally suited to fine detail work
SIDE FEED refers to air brushes on which material enters at the side of the air brush through a side attached color reservoir. This type of air brush operates best at approximately 12 PSI. The side feed also allows the cup to be swung for and aft in an arc to allow for variations in brush position while painting. (ref. Badger Airbrush Co.)
For me, the bottom feed from a bottle works well for my general use. That said I can certainly see benefit to the use of a paint cup when doing fine weathering work with an air brush. The control of a gravity feed is best in this case. However, since most of us don’t want to buy more than one air brush, consider getting an air brush that you can change from a bottle to a cup readily. This gets the best of both worlds with the minimum of cost.
John

Side mount open cup air brush

Permanently attached closed cup (cap on it) gravity feed air brush. Ideal for graphic arts

The familiar bottle for the underfeed, bottle fed air brush.

Air brush with bottle attached. This bottle and fitting can be slipped out of the air brush and a cup put in its place on this particular model