60 ■ POPULAR WOODWORKING
Airless spray guns are commonly
used by painters for coating large
surfaces such as buildings. Air-assist-
ed airless spray guns are commonly
used in factories and large produc-
tion shops and are quite expensive.
So I’ll limit this discussion to the fi rst
three types used by most amateurs
and small professional shops.
Each of these types work by using
air to turn a liquid stream of fl uid
into a mist, a process that is called at-
omizing. There are two sources of air:
compressors and turbines. Compres-
sors produce air under high pressure.
Turbines produce high volumes of air
under low pressure. Both can be used
to power HVLP (high-volume-low-
pressure) spray guns.
The way compressed-air HVLP
spray guns do this is by pinching the
air coming through the gun so that
the pressure is greatly reduced when
the passage is opened up again.
Both of these types came on
the market 30-to-40 years ago and
are now so widely used because of
the softer spray they produce that
it’s now diffi cult to fi nd the older
high-pressure spray guns except on
the used market.
So if you’re thinking of buying a
spray gun how do you choose which
one to get?
You have three choices to make:
the type you want (conventional,
conversion HVLP or turbine HVLP);
how much you’re willing to pay; and
the brand.Type
If you already have a compressor
large enough to operate a conversion
spray gun, or if you intend to buy a
compressor for other uses, such as
running pneumatic tools, then you
should buy a conversion HVLP spray
gun. These guns will cost you $200
or more, but you’ll get the highest
quality results and this will be your
total expense except for exhaust.
If you don’t already own a com-
pressor, have no other need for one,
and don’t expect to be doing produc-tion work, you should buy a turbine
HVLP system. Your total expense
will be less and you’ll get excellent
results. Turbine HVLP is the way
to go for most amateurs and small
woodworking-shop professionals.
Another advantage of turbine
HVLP systems is easy portability so
many painters who do their painting
on site buy this system.Cost
Buying a spray gun or spray system
is similar to buying a table saw.
With a table saw, the more you pay
the better the durability (you can
operate it for longer periods of time
without it wearing out) and the
more accurate the settings. With
a spray gun, the more you pay, the
better the durability and the better
the atomization. You should always
buy the best quality (most expen-
sive) you can aff ord.Brand
There is a lot of competition among
companies, so you usually get what
you pay for no matter which brand
you choose.
The most important diff erence
among brands is availability of
service. If anything should go wrong
with your spray gun you want to
be able to get it fi xed. You may also
want extra parts, like various sizes
of needles, nozzles and air caps or
you may want the spray gun rebuilt
after a number of years of use.
Service is usually provided by the
distributor and not by the manu-
facturer so you should look for a
distributor in your area that provides
service. If you decide to buy by mail
order, do the same. Find a mail-order
company that will take care of you.
Beyond these three consider-
ations you may look for special
features, but most spray guns of
equivalent price are very close to the
same in features. PWBob Flexner is the author of Flexner
on Finishing, Wood Finishing 101, and
Understanding Wood Finishing.Spray Gun Basics
5 6
7
5-6 The way to judge the quality of
atomization you’re getting is to spray a
short burst of fi nish onto cardboard or
brown paper and look at the edges of
the pattern. How big are the dots? The
picture on the left shows good atomi-
zation. The picture on the right shows
poor atomization.
7 Poor atomization leads to increased
orange peel because the fi nish has
more diffi culty fl attening out.