On May 26, 8:44 am, "dadiOH" wrote:

Lap I guess. Say you have a horizontal surface...do you start with the edge
closest to you - in which case the spray from each pass would sort of
feather out to the not yet sprayed area - or the area farthest from you in
which case the spray from the current pass would feather out into the
previously sprayed area?

In a perfect world, it wouldn't matter as the overspray/drift would
simply melt into the finish wherever it goes on the surface, providing
the surface is still wet.

However..... experience has taught md differently based on the "hot"
materials I like to spray. When the heat is on down here in South
Texas, I cannot spray a door with enamel and get to the other end
without the overspray turning to dust and sitting on the previously
sprayed areas.

Here's my solution.

Assume you are spraying some like a house door, laying flat. This
would also work on a table, since flat is flat. Since I know I have
the hose behind me and ** I will ** drag it across the previously
sprayed area, I tend to start away from me, and work my way back
towards the turbine, keeping the hose behind me. Maintaining the
proper gun position and distance to target is imperative here, as you
want to minimize any drift.

The natural feel is to tilt the gun back slightly, and this will push
overspray onto your previous finish. You need to keep the gun
perpendicular to the surface to minimize this problem.

Make your first pass by pointing the tip of gun at the edge of the
work, then spraying. While half of your spray will hit the floor, you
will start with a half lap, which will make your edges cleaner and
will make your finish thickness uniform over the piece. Likewise,
finish off the same way.

OTOH, if you are using long finishes such as alkyds and clear polys,
this isn't as crucial because they have such a long cure out. The
overspray (unless there is a lot) will simply melt into the previously
sprayed areas.

But remember, when shooting anything out of the HVLP, you have thinned
it (unless you get into a 3 - 4 stage machine), and it will dry out
faster. With latex, poly, long enamels, it shouldn't be a problem.

With lacquers in higher temps (+80F) it can be.

This reinforces the fact you should keep a recipe book of notes on
material, humidity, % thinned, temps, etc., when tailoring your
specific formulas.

When I spray vertical surfaces, I always start from top and go to
bottom since the hose stays out of the way, and the drift will work
downward anyway.

As a tip, you need to remember that these turbine units put out a
certain amount of air. With baffles on the machines, it may not be
too bad, but it can get the air swirling pretty good, putting dust in
the air that will foul your finish.

Why no one ever does this or uses it as a tip, I don't know... Put
the turbine on a box or stand, and keep it 24" off the ground. If you
think it will fall over, off, etc., secure it with a bungee cord.
This is crucial.

Keeping your turbine out of the crucial 8" constantly moving dust
layer will cut your dust distribution by 75%. Think of all the dust
and debris on the floor of the shop or spray area, and then think of a
vacuum cleaner or shop vac blowing all that stuff around. Not good,
right? I must say, I seem to be the only one that has noticed this,
though.

Also, it will keep the filter on the machine clean. One old complaint
about the use of HVLP guns is that they get hot, then they spray hot
air into the finish, fouling the finish. If you find this to be the
case, stop spraying.

Most of the time, when an HVLP turbine overheats, it is because it is
working too hard. It works too hard because the air filter is clogged
with dust and debris (remember keeping the machine off the floor?)
that accumulates when the machine filters the air before sending it to
the gun. It strangles the air flow to the turbine. Dirty filters are
a no-no, and as cheap as they are I always keep an extra on hand.

One more thing, as a great way to keep that overspray (I shoot stuff
that is hot enough that it is powder before it drifts 3' to the
ground) is to put a cloth drop cloth of some kind under your spray
table. A crumpled drop cloth seems to catch a great deal of the drift
and keep it from circulating while you move around spraying your
piece.

Robert