The process
by which the paint mixture is broken up into finely
separated particles. Atomization allows the paint
mixture to be applied to the substrate in an even,
well-distributed manner.
Air
pressure
The air
required to achieve atomization. Air pressure should be
kept to the minimum required to achieve atomization and
control of the fan shape.
Bounce
back
Paint
particles bouncing back from the surface being painted
due to high air pressure
Closed
film
A closed film
is achieved only when a full wet coat is applied giving
an even gloss appearance
Coat
The total
amount of paint applied in one application.
Cross
coat
The
application of the paint in both vertical and horizontal
planes as one coat
Fan
shape/pattern
Fan shape can
be controlled or changed by using an adjuster on the
spray gun. A narrow fan or needle jet is used for
spotting or edge painting, a wide fan shape is used for
larger areas. A narrow fan applies a high volume of
paint relative to the surface area being painted,
resulting in a tendency for runs and sags.
Fanning/arcing
The spray gun
must be held equidistant from the surface being painted.
An arcing motion changes the distance resulting in
uneven film build and overspray.
Flash
off
The time
given between coats, necessary to allow evaporation of
the solvents. Adequate flash-off reduces the risk of
solvent entrapment leading to loss of gloss, solvent
boiling, popping, blistering, and sags or runs.
Fluid
pressure
The volume of
material required to achieve atomization at the spray
gun tip. Fluid pressure is critical. Too little will
result in a thin film Too much will result in runs, sags
and orange peel.
Gun
speed
The speed at
which the gun moves over the surface being painted.
Gun
or target distance
The distance
away from the surface that the spray gun is held.
Healing/toeing
This is a
paint film defect caused by holding the spray gun at an
incorrect angle relative to the surface being painted,
resulting in heavier film build either at the bottom or
top of the stroke.
Mist
coat
Tack coat or
tie coat are terms that describe the first light coat of
paint. This coat will not achieve a fully closed film,
but is used as the base for subsequent coats.
Overlapping
Part covering
the previous stroke. Overlapping can be expressed in
percentage terms (i.e., 25% overlap)
Overspray
The paint
which becomes airborne and resettles onto the paint
film. Care must be taken to avoid overspray on areas not
intended to receive the paint.
Pass
The number of
strokes it takes to cover the area being painted.
Stroke
A single pass
of the spray gun across the area being painted. Normally
no more than one meter (3 feet) in length.
Triggering
The act of
releasing the spray gun trigger at the end of each
stroke.
