· Internal mix gun: In an internal-mix gun, the
volume has not been reduced at the tool by undersized
h o s e , h o s e m e n d e r s , u n d e r s i z e d bu s h i n g s , o r
air and the paint are mixed within the
quick-connect couplings that restrict the air flow.
internal-mix air cap. In this type of gun,
atomization of the paint is coarse, and the spray
pattern is fixed. The gun works only with a
pressure feed, but the pressure is lower and the
In the Navy, the basic painting equipment includes
amount of air used is less than for the
spray guns and their associated equipment, paint
external-mix gun. Because atomization of the
rollers, and paint brushes. Each of these items is
paint is coarse, more paint is applied on each
discussed in the following subsections.
pass. See figure 1-12.
A spray gun is a precision tool in which air and
paint are separately directed into the area where the
paint is atomized before it is sprayed on the surface
being painted. The mixing area may be outside or
inside the spray cap of the gun.
Spray guns are classed according to where the air
and the paint are mixed (external or internal), how the
air is controlled (bleeder or nonbleeder), and how the
gun is supplied with fluid (suction feed or pressure
· External-mix gun: In an external-mix gun, the
air and the paint are mixed outside in front of the
external-mix air cap. This type of gun requires
Figure 1-12.--Internal-mix air cap.
high air pressure; thus, it uses more cubic feet of
· Bleeder gun: A bleeder gun allows the air to
air per minute than an internal-mix gun.
Atomization of the paint is extremely thin and
leak or bleed from some part of the gun to
the size of the spray pattern can be controlled.
prevent the air pressure from building up in the
There is no wear on the nozzle. By the use of
hose. In this type of gun, the trigger controls the
different nozzles, an external-mix gun works
fluid. The gun is generally used with a small air
with both suction and pressure feed systems. See
· Nonbleeder gun: A nonbleeder gun is equipped
with an air valve that shuts off the air when the
that has a pressure-controlling device.
· Suction-feed gun: A suction-feed gun has a
suction-feed air cap that draws the fluid from the
container by suction in about the same way that
an insect spray gun operates. The suction-feed
guns are usually used with one quart (or smaller)
containers. See figure 1-13.
· Pressure-feed gun: A pressure-feed gun
operates by air pressure. The air pressure forces
the fluid from the container into the gun. This
type of gun, with a pressure-feed air cap, is used
for large-scale painting. See figure 1-14.
Figure 1-11.--External-mix air cap.