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Operating Instructions
Introduction
The spray gun is a vital link in any fin-
ishing application. In addition to oper-
ating the spray gun properly, tech-
niques of surface preparation and paint
preparation must be understood. These
instructions will explain the differences
among various spray technologies and
serve as a guide in the proper opera-
tion and techniques of spray painting.
Refer to the Replacement Parts Manual
for model specific information.
SPRAY GUN TERMS
Atomization - Conversion of bulk liq-
uid to spray droplets (mist).
Bleeder – In this mode, air passes con-
tinuously through the gun whether
spraying or not. This mode is generally
used when the air is supplied by a con-
tinuously running compressor that does
not have a tank.
Bleeder/Non-Bleeder – Indicates
whether air flows through the gun con-
tinuously or as the trigger is pulled.
External Mix – Process where the air
and paint are mixed just after leaving
the nozzle. This type of mix should be
used for fast drying paints and when a
high quality finish is needed.
Feed – Method used to bring paint into
the gun for spraying.
Fluid Control Knob – Used to control
the amount of paint being mixed with
air.
Gravity Feed – Method of paint feed
similar to the siphon feed method.
However, the cup is inverted to create a
positive fluid pressure at the nozzle.
Internal Mix – Process where the air
and paint are mixed inside the air cap
just before being sprayed. This method
is best for heavy bodied, slow drying
paints and can only be used with the
pressure feed method. Do not use fast
drying paints with internal mix. The
paint will dry inside and quickly clog
the air cap.
Mix – The mixing of paint and air when
spraying.
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Non-Bleeder – In this mode, air flows
only when the trigger is pulled. This
type of operation is used with a com-
pressor equipped with a tank or with a
large factory air system.
Paint Tank – An auxiliary pressurized
paint reservoir that allows continuous
spraying of large amounts of paint with-
out stopping for refills as with a canister. It
also allows using the spray gun at any
angle without causing paint to drip.
Pattern Control Knob – Used to form
the proper pattern (size and shape) of
paint as it is sprayed from the gun to
the workpiece.
Pressure Feed – Method of paint feed
where a canister or paint tank is pressur-
ized to force paint to the gun. Either
internal or external mix air caps are used
with this method. Pressure feed is gener-
ally used for spraying heavy bodied
paints or for large size projects.
Siphon Feed – Method of paint feed
where atmospheric pressure creates a
partial vacuum to siphon paint to the
gun. Only external mix air caps are used
with this method. Siphon feed is used
with light bodied paints.
Viscosity – A measurement of the
resistance to the flow of liquids.
CONVENTIONAL VS. HVLP
Conventional spray guns use a much
higher air cap pressure to atomize
paint than HVLP spray guns. This results
in more overspray and a lower transfer
efficiency.
HVLP, electrostatic and airless processes
are currently the only compliant spray
methods that meet the strict 65%
transfer efficiency criteria required by
some air quality management districts.
This enhanced transfer efficiency results
in a significant material savings com-
pared to conventional spraying. Check
local, state and national regulations
that may be in effect before perform-
ing any spraying operations.
HVLP spraying is a growing trend in the
finishing industry due to its environ-
mental friendliness. By definition,
dynamic air pressures in the air cap
must be 10 psi or less to qualify as
2
Gravity Feed Spray Guns
HVLP. A soft, low
Conventional
velocity pattern is
produced which
increases control
and reduces
bounceback and
HVLP
overspray (See
Figure 1). For
these reasons,
Figure 1
HVLP is also well
suited for spray-
ing parts with recessed areas.
Spray Gun Set-up
The pressure for atomization is con-
trolled at the air source. The amount of
fluid is adjusted by the fluid control
knob, the paint viscosity and the air
pressure.
The gravity feed cup screws onto the top
of the gun body creating a positive fluid
pressure in the nozzle (See Figure 2).
Figure 2 - Gravity Feed Cup Set-up
Preparation
1. Thoroughly mix and thin paint in
accordance with the paint manufac-
turer's instructions. Most materials
will spray readily if thinned
properly.
2 Strain material through cheese cloth
or a paint strainer.
3. Fill the canister about 3/4 full and
start the air compressor.
4. Set up a piece of cardboard or other
scrap material to use as a target and
adjust for best spray pattern.
Filtered,
Regulated
Air Source
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