all you ever wanted to know about spray painting
Bill Noble
first, some credentials - for hobby (not business), I have
painted at least
10 cars, including a couple of porsche, more than a couple of
cadillacs, and
various other things. I have used laquer (both acrylic and
nitrocellulose),
enamel, polyurethane, epoxy, and probably some other stuff I
forgot. I
have three air compressors (a tiny one by binks, a 2 hp
craftsman and a real
industrial 5 hp unit) - and I have a good airbrush (paasche),
several siphon
guns and a binks hvlp gun (of the $450 variety).
Ok, so I know something of what I speak, so now I'll yack for
a bit.
1. water and oil in the air - both of these will settle out if
the air cools
down - cheap compressors or really hot air on a humid day will
cause
trouble. But if you fill a container and bring it home
anything will settle
to the bottom (so be sure to extract air from the top) - it
will not be a
problem.
I did have trouble with water, from time to time, from the
crafstman unit,
but my industrial unit has an intercooler between the two
compression stages
and there is never water or oil in the air from it (this is
sooooo nice).
2. beware of cheap spray guns. I have acquired several and
they have cost
me more in paint (to redo the work) than I paid for them -
they are all gone
now. a good gun will have excellent control, will produce a
fine and
regular mist and little overspray. a poor gun will have an
irregular spray
pattern and may spatter. My hvlp gun lays out a pattern that
varies from
about 0.25 inches in diameter spot to a line about 18 inches
long - the spot
is useful for spraying just a bit into a tight recess without
making
anything run, the line is useful for painting body panels -
otherwise you
spend all day (compare to a spray can - output is a 1 inch
(aprox) circle -
the hvlp gun will spray about a quart of paint in 2 or 3
minutes - maybe
faster if you are just emptying it - you need this with big
stuff.
3. there are siphon guns and the hvlp guns that have the paint
container on
the top - I believe these are called gravity feed. with a
siphon gun I
usually spray with 30 to 40 psi at the regulator (which is
about 6 to 8 feet
from the gun) and with hvlp, 15 pounds or less - so you get a
fine mist with
the siphon gun and lots of overspray, you can get a heavy mist
with very
little overspray with hvlp.
4. there are things called touchup guns which would be more
appropriate for
radios - and cheaper to - I'd still go for hvlp.
5. beware cheap air compressors - its the pump, not the motor
that matters.
what many taiwan air compressors do is put a large motor on a
small pump -
so you see a 5 horse air compressor for $299 or something and
it seems like
a steal. I've looked at these, read the data sheets, and so
on - one of
those cheapie 5 horse compressors puts out about half the air
as my 2 horse
crafstman and less than a tenth the air of my industrial grade
5 horse
compressor. you are better off with a smaller motor and a
larger (and
better quality) compressor - you will get more air, and you
will get a lot
less water and oil.
ok, did I forget anything? oh yeah - about 10 feet of 1 inch
water pipe
between the compressor and your air outlet, inclined towards
the compressor,
is a good thing - it lets the air cool down and the residual
water condenses
out and trickles back to the compressor. a water trap is
nice, maybe
necessary if you are on the east coast where humidity is high.
----- Original Message -----
From: "Bill Jeffrey" <NOSPAMa...@aspi.net>
Newsgroups: rec.antiques.radio+phono
Sent: Friday, July 14, 2000 3:13 PM
Subject: Re: Refillable Spray Can
> Bill -
>
> Air from a gas station, as from many other piston
compressors, often
> contains a bit of oil. I would think that oil would mess up
a lacquer
> finish big time. Have you experienced any problems like
this?
>
> Bill Jeffrey
> ----------------------
>
> Bill Noble wrote:
> >
> > This is convenient if you really want to test out some new
> > mixture in a spray can - however, you will actually have
at
> > least as good results if you get a small air brush. You
can
> > convert an old freon container (or propane) to an air
pressure
> > resivoir and that will drive a small air brush for many
tens
> > of minutes - you charge it up with pressure from a gas
> > station. A really good air brush costs $80, but there are
> > cheaper ones.
> >
> --
DUSTYMUSTY
pressure is highest (BEFORE the tank and, especially, before the regulator).
Some compressors come with finned pipe between the cylinder outlet and
the tank to achieve this cooling. Those that don't can easily be
retrofitted
with a length of copper tubing snaked into a suitable coil or squiggle
(thelonger the better). The outlet of the cooler / condenser can go
directly to
the tank or, better yet, to a "coalescing" separator that causes water and
oil mist to aggloberate into larger drops that settle out and can be purged
from the bottom of the chambers. These gizmos are expensive if you buy them
through regular supply houses like Grainger, etc., but they often show up on
auction sites, and they usually go cheap because very few folks understand
what they are or how to apply them.
A small continuous or periodic purge from the bottom of the tank is also a
real good idea, to prevent accumulation of liquid and eventual rusting and
shedding of rust dust.
A cartridge type air filter in the line AFTER the regulator and as close as
practical to the gun is a good idea too. It's amazing how much "space dust"
will spontaneously generate inside the hoses, no matter how carefully you
cap
and store them.
For real finicky oil-sensitive applications, you might want to consider an
oil-free compressor. I think DeVilbiss still makes units that use flexing
diaphragms instead of oil-lubricated pistons. The downside of these is
maintenance; the diaphragms need frequent replacement.
Doug
Eddie Brimer
combos fairly inexpensively. any auto finish supplier can supply you with throw
away filters that screw into the inlet on the gun. a little fish-eye preventer
and retarder on those hot days will help with agood finish too. a tip on the
equipment. don't go cheap and don't go small. a good compressor will have
coolers installed at the factory. the big motor/little compressor ripoff is
common. oil in the lines is ussually caused by worn rings or cylinders. cheap
guns are a pain in the butt. you might as use a spray bomb. (which will give
great results by the way.) in other words, you get out of it what you put into
it.
Eddie Brimer
2480 S. Beersheba Rd.
Sharon SC, 29742
visit my web page "THIS OLD RADIO"
http://members.aol.com/EB062559/THISOLDRADIOINDEX.html
Bill Turner
THE TANK. I AM ADVERSE TO WATER COLLECTING IN THE TANK AND RUSTING IT
OUT. I UNDERSTAND IT BECOMES LETHAL.
disregard caps, visual problem
Bill Turner WA0ABI
1117 Pike Street
Saint Charles, MO 63301
636-949-2210
Bill Noble
major intercooler - even with an intercooler, the air is still
pretty hot when it enters the tank, it sits in the tank and
cools down, then cools more as it travels the hoses. that's
why you need it some distance after the tank. If you had room
for 20 feet of 3/4 inch copper tubing to spiral around between
the compressor and the tank, then you probably could collect a
reasonable fraction of the water before it gets in the tank.
with my sears unit, if I was painting a car, the tank would
stay pretty dry - e.g. the air was so hot it didn't release
much water even in a 20 gal tank. the siphon gun I used then
needed 7.2 cfm and that was exactly the compressor's capacity
so it pretty much ran all the time. the compressor got hot
enough to burn off the paint (just like a lawn mower engine)
and after two cars I had to rebuild it (cracked a ring and
burned a valve). With the larger industrial unit, I collect
most of the water in the tank, and then about 10 ft away there
is another water trap, and then at the end of a hose I place a
third - so I have pretty dry air.
got all the traps and stuff at swap meets and surplus sales -
I doubt I paid more than $10 for any item, most were a dollar
or so - except of course the nice compressor, $800 rebuilt
from a specialist that does this work.
"Bill Turner" <dial...@webtv.net> wrote in message
news:16721-39...@storefull-126.bryant.webtv.net...
Eddie Brimer
>THE TANK. I AM ADVERSE TO WATER COLLECTING IN THE TANK AND RUSTING IT
>OUT. I UNDERSTAND IT BECOMES LETHAL.
>
>disregard caps, visual problem
>Bill Turner WA0ABI
>1117 Pike Street
>Saint Charles, MO 63301
>636-949-2210
>
>
won't work bill. at least not in any reasonable set-up. on the small
compressors that most people use here, (less than 10 cfm) if you are spraying,
the compressor runs almost without stopping. you are pulling in humid air at
outside temperature, say 80-100 degrees and compressing it. the process of
compression adds heat to the air. it removes none of the moisture. to remove
the moisture, you must cool it. and give it a surface to condense on. (the
tank and filter) and a place to go. hopefully the bottom of the tank and the
water trap. as i said, most good compressors come with a cooler before the
tank. if you put a trap/filter combo after the tank, most of the condensation
will occur in the filter and tank. you will have further cooling in the air
lines. a filter at the gun will remove most of it. if you are spraying on a
moisture laden day, the moisture can be put back into the mix when it leaves
the gun. as far as being lethal, all tanks, if not drained periodically will
fail. from the moment the tank leaves the factory it is rusting. if it is a
quality tank, the compessor will wear out long before the tank becomes lethal
if it is maintained. however, if you buy a cheap tank that only meets minimum
safety requirements...i suppose anything could happen.
John Bartley
- I can verify that Bill. we have been thru' two compressors in my
repair shop (lawn equipment repairs), but only because the compressors ran
out of life, and it's cheaper to replace and sell the old one than to
rebuild. We drain thru' a tank bottom drain cock every week during the
summer and evry month in winter time, and have seen only a bit of rust come
out with the condensation. When I paint, I put a dryer about 6 feet down the
line from the tank and have never had fish-eyes, even without fisheye
eliminator.
--
============================
= regards - John Bartley =
= Ottawa, Canada =
============================
"Eddie Brimer" <eb06...@aol.com> wrote in message
news:20000715175027...@ng-bd1.aol.com...
> >I THINK I WOULD PREFER THE MOISTURE SEPARATOR BETWEEN THE COMPRESSOR AND
> >THE TANK. I AM ADVERSE TO WATER COLLECTING IN THE TANK AND RUSTING IT
> >OUT. I UNDERSTAND IT BECOMES LETHAL.
> >
> >disregard caps, visual problem
> >Bill Turner WA0ABI
> >1117 Pike Street
> >Saint Charles, MO 63301
> >636-949-2210
> >
> >
>
> won't work bill. at least not in any reasonable set-up. on the small
> compressors that most people use here, (less than 10 cfm) if you are
spraying,
snipped