Fred Parker on thu 25 jan 07
Ingeborg:
"Overspray" can mean lots of different things from "everything in sight
gets coated" to a near-negligible amount of mist in the air. Remember
that for overspray to be a real problem, it must contact a surface while
it is still wet. If the overspray droplets dry before contacting
anything, it becomes harmless dust that can be removed by a simple
dusting. Factors that control how wet or dry overspray is include the
size of overspray droplets, relative humidity, distance from the spray
source, amount of time suspended in the air etc.
The airless sprayers that housepainters use produce a relatively coarse,
wet spray which tends to land on the wall and not become suspended as
overspray. These systems are hydraulic instead of pneumatic. They work
more like a Windex sprayer by pumping the paint out at a very high
pressure, which breaks into droplets when it hits the air. A conventional
sprayer typically atomizes the paint by subjecting a syphoned stream of
paint to a high pressure blast of air, a process which produces MUCH
overspray.
Painters using airless equipment sometimes use a portable shield that
looks something like a giant putty knife and can be held against a wall to
block overspray from the immediate area (for instance, when painting a
window frame.) If NO overspray is your criterion, then no spray equipment
will work. However, if you can live with SOME overspray, most of which
will probably be dry dust, then airless might beat the roller if you have
much area to cover.
One word of warning: DO NOT accidentally or intentionally spray yourself
with an airless sprayer! The pressure is 1500-2000 psi or so. It will
inject paint under the skin, which demands IMMEDIATE medical attention.
If it happens, do NOT think it will heal in a few days -- it won't.
Ignoring it can result in amputations or worse...
On Wed, 24 Jan 2007 22:03:39 -0500, Ingeborg
wrote:
>Fred,
>
>Thanks. I have been to a number of paint stores to get input and they
have
>all pretty much said "to spray means to overspray" I thought perhaps the
>clayart community would have the secret. Lo and behold, there appears to
be
>no secret which means I will be rolling for days and days on end since I
>cannot tolerate overspray.
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