Some Thoughts On
Safe Locations For
Bruce W. Maki,
There are many places I have done spray
painting and wood finishing: Outdoors, garage, basement, and
professional spray booths. I believe spray finishing can be done
safely in each environment, providing sensible precautions are
Spray painting or spray finishing can be dangerous,
hazardous to your health, and cause serious property
This article should not be viewed as
"instructions" or "advice". This article
is for entertainment purposes only.
If you undertake any spray finishing project, then you
are working at your own risk. Under no circumstances
will HammerZone.com or it's publisher be held liable for
any damages caused by your actions.
Be aware that
I am not an expert on this
subject. If you chose to pursue spray finishing, I recommend
that you do additional research... I do not know
everything about this subject. See
Recommended Reading at the end of this article and read the
Spray Finishing Outdoors:
Perhaps the most logical place to do spray
finishing is outdoors. The benefits are obvious... lots of space,
more-than-adequate ventilation, and little or no risk of explosion.
But spray finishing outdoors has some potential problems:
Temperature Control: Most paints,
stains and urethane products have a narrow temperature range that is
suitable for their application. Here in Northern Michigan I could
spray outdoors almost any day in the summer months, but that leaves
about two-thirds of the year where it's too cold. In warmer climates
it might be possible to do spray finishing during the cooler times
of the day, perhaps early morning or late evening. Spraying in
direct sunlight might not be the best idea because when coatings dry
too fast many problems can arise.
Rain: What more do I need to say?
Bugs, Dust and Other Junk: Bugs like
to take a break from flying, and they are certain to discover your
project. Maybe oil-based paint, stain or urethane smells like food
to certain bugs. If it's warm and sunny enough, flies might not land
on your work because they will need to stay cool in the shade.
There's not much anybody can do to control
the dust or pollen that falls in their backyard, but after it rains
there is usually less dust in the air. However, after it rains there
is often a chance of... more rain. I'll look at the National Weather
Service's website to check the radar for my area.
If there are trees around, it seems that
there's always something falling... leaves, twigs, bits of bark,
bird poop, squirrel fur, etc. You can't win. I guess it's a good
idea to stay away from tall trees.
overspray is impossible, but it can be monitored and there are ways
to control it. Distance is your friend. I wouldn't spray outdoors
unless I had lots of open land and great distances between my spray
gun and anything owned by someone else. How much distance? I don't
know. That's the problem... overspray might travel hundreds of feet
before it dries into a dust-like powder. It depends on how fast the
droplets dry, which is hard to predict.
I will only spray outdoors if the wind is
very light and if the direction of wind blows the overspray away
from anything valuable, such as the neighbor's house or (most
important) cars. I frequently stop spraying and look around
for evidence of overspray getting on nearby objects, and faraway
objects too. I have often been surprised by the distance overspray
An Overspray Horror Story:
When I was in college I had a
friend who had a summer job with a maintenance crew
that did regular repainting of a big steel highway
bridge. They brush-painted the entire bridge every few
years. I asked why they didn't spray paint it, and my
friend explained: Years before they had spray
painted the bridge (a lovely deep green) and later the
owner of a car dealership a hundred feet below and few
hundred yards to the south pointed out the green overspray on
every car in his lot. The maintenance company had to
spend $30,000 to remove the overspray from all those
Which raises the
question... How do you remove overspray from cars?
I'm guessing that it involves buffing the car with an
buffer and the appropriate buffing compounds. I've
article about buffing out scratches for another
website that I publish. I suppose the same process
(without the sandpaper) would work for removing small
specks of overspray. But... it takes a lot of time.
A few years ago I repainted the cab of my truck.
I disassembled the body panels and painted them
outdoors on sawhorses or laying across my small
read about this repainting job on yet
another website that I publish.
article about installing an extension to a
privacy fence, I spray painted sections of
lattice with a Wagner power sprayer.
Wagner power sprayer makes A LOT of overspray,
so it's important to keep some distance from
anything that could be damaged by overspray.
In the above two pictures I was
working in the back yard of a rural house I lived in several
years ago. That house had five acres of land and there was
lots of open farmland on three sides of the property. The
nearest house was at least 300 feet away. I had no problems
with overspray getting on anything valuable.
Spray Finishing In The Garage:
A garage would be the next obvious choice
for spray finishing locations. It's out of the sun, the rain, and
birds rarely fly over your project. In cold weather a garage may not
be a suitable location for spraying, unless it's insulated and
If adequate cross-ventilation can be
achieved, a garage could be a safe place to spray paint, stain or
urethane. What exactly is "adequate ventilation"? I don't know. Some
characteristics of adequate ventilation: There are no explosions,
and nobody gets sick, light-headed or dizzy from the fumes. And
nobody develops cancer or brain damage later in life.
There are only a couple of times that I've
done any spray finishing in my garage. When I did, I opened the
garage door about 12 to 24 inches, I opened at least one additional
door or window, and I put large box fans in places that would create
a good cross-flow of air.
Since the vapors from most common solvents
are heavier than air, they will sink. It makes sense to place
fans at floor level, blowing air into the garage at one side and
blowing air out the opposite side. It doesn't make sense to fight
the prevailing wind direction... it's better to place the incoming
fan on the windward side of the building (the side exposed to the
wind) and the outgoing fan on the opposite side.
I suppose a fully-opened garage door would
do the best job of preventing vapors from building up, if there is
another door or window open and a fan running. But... when the door
is opened completely there may be a greater chance of overspray
getting outside and onto something valuable. (Isn't this a
Spray Finishing In The Basement:
Most of my spray finishing has been done
indoors, in a basement. While it hasn't happened to me yet, THERE
IS ALWAYS A CHANCE OF BLOWING UP THE HOUSE. Seriously.
When I've done spray finishing in a
basement, I ALWAYS do the spraying directly in front of an
open window with one of more large fans blowing the air OUT. I also
place another fan in a window on the OPPOSITE side of the building,
blowing air IN.
I only use fluorescent lighting around my
spray area. I don't use halogen work lights because they get so hot
I fear they might ignite the vapors. I've heard about fires where
that happened. Even regular incandescent lights might be capable of
igniting the vapors.
In this photo you can see the fans in the open
window behind me. Those are 20 inch box fans,
which I bought at Home Depot for about 15 bucks.
The grills and blades on these fans developed a
coating of stain and urethane, which tells me
that they are doing their job.
Also, note the plastic sheets beside
me. I rigged up 2 of these by cutting a sheet of
polyethylene plastic, rolling a 1x2 around each end and
stapling it. The upper board is screwed to a beam above.
When done spraying I just roll up the plastic around the
lower board and hold it up with Velcro straps. These sheets
do a great job of keeping overspray away from the rest of
Where Do The Solvent Vapors Go?
While writing this article, I looked online
for information about the vapor density of various solvents. I
was under the impression that most of these vapors were lighter than
air and therefore would rise upwards. I was wrong. Just because you
can smell the vapors doesn't mean they are all rising up. It turns
out all of the common household petroleum solvents emit vapors that are
In the above photo, it's entirely possible that flammable vapors
were gathering on the floor behind me. Luckily, I had another fan
just behind the camera, blowing air across the floor towards the
window. This probably stirred up the air enough to prevent a
dangerous ponding of vapors.
BUT... five feet behind the camera sits my
gas water heater, which has a standing pilot light. A pilot light is
a common cause of flammable vapor fires. If the vapors had been able
to flow back along the floor, I could've had a big problem.
The next time I do any spray
finishing in my basement, I will take a small tilting fan and
place it on the floor near the wall, blowing air upwards toward the
window. That should keep fumes from building up near the floor. The
goal is to bring fresh air in a basement window, blow air
across the floor towards the spray area, then blow air up
towards the out-blowing window where my two large fans will suck the
air and vapors outside.
Just to be on the safe side, it would be a good idea to
turn off the gas water heater, so the pilot light goes out.
Of course, that means the pilot needs to be re-lit later, and there
might not be enough hot water for anybody else in the house.
Overspray Problems: Since the fan
blades get coated with stain and urethane, I knew that overspray was
getting outside. My neighbor's house is about 12 feet away from that
open window. Realizing that there was a chance that some overspray
could reach their house, I rigged up a simple deflector to make the
air turn upwards. I just placed a wheelbarrow on it's side about 3
feet from the fans, so the air and overspray were deflected upwards
or back towards my own house. I didn't see any traces of overspray
on anyone's siding.
Spray Finishing In An Industrial Spray
Industrial paint booths are designed for
spray finishing. Most have built-in furnaces to heat the air in cold
weather, and some have air conditioning to keep the air cool in hot
weather. All are designed to minimize or eliminate the risk of fire
While I'm not going to suggest that you
spend tens of thousands of dollars on a professional-grade paint
spray booth, it might be possible to borrow or rent one.
You might find a custom-cabinet company in
your area that has a spray booth. Maybe they aren't using their
booth 100% of the time, and maybe they would be open to the
idea of letting somebody else use that booth for an hour a day over
a couple of days. The bigger problem is: Where do you park your
project while it dries, and where do you do the
scuff-sanding that is required between coats of urethane? If they
have a small section of their shop that you can borrow/rent to scuff
the finish before applying the second coat then this idea should be
If you were going to try this approach, it
would be best to provide your own spray gun (make sure their air
hoses can connect to your spray gun, or get some fittings that will
work), bring your own stain, urethane, and solvent for cleaning up,
and bring your own organic vapor respirator.
If you stayed out of the way of their
workers, didn't interfere with the flow of their projects, and worked
around their schedule, this might be a feasible solution for
somebody looking to spray finish their own furniture or wood trim.
A more likely place to do spray finishing is
a local independent auto body shop. I'm referring to body
shops that are not part of a large chain, and are not
associated with a new car dealership. I've learned that some smaller
independent auto body shops find it increasingly difficult to make a
decent profit doing repair work that is paid by insurance companies.
Consequently these shops sometimes prefer to do custom work, car
restoration, and special non-automotive painting/finishing jobs.
I suppose a do-it-yourselfer could call some
of the smaller auto-body shops in their area and (if they have a
spray booth) ask if they would be willing to rent out their spray
booth and a small area of their shop. I've seen it done before, but
please understand that not every body shop would be willing
to do this. If you are looking for a safe place to apply spray
finish, it might be worth a phone call.
same suggestions mentioned earlier still apply: Bring your own tools
and materials, and don't make their life difficult.
photo, the painter is spraying a car hood. Note
the vent inlets down low on the wall. This spray
booth is big enough to fit a large car, pickup,
or SUV, so it's big enough for any furniture or
amount of trim.
This photo was taken for
an article on BodyShopZone.com, which I
publish with a friend who is an experienced auto
A properly equipped industrial paint
booth is the only location that I would actually
recommend to anybody wanting to try spray finishing.
While I've done spray finishing outdoors, in
my garage and in my basement, I'm not going to recommend
those locations to anybody. If you chose those locations, that is
your decision, and you bear the consequences.
Warnings About Do-It-Yourself Spray Finishing:
Whether applying paint, stain,
urethane or lacquer, there are some bad things that can
happen when spray finishing.
Explosion and/or Fire:
Many wood finishes are oil-based and use flammable
solvents such as mineral spirits, acetone or lacquer
thinner. When these finishes are sprayed, the solvent
vapors can be explosive. Keep away from open flames or
hot surfaces such as light fixtures. Spray
finishing requires lots of ventilation.
Health Risks Of Paint Fumes:
Petroleum solvents can make you feel light-headed, but
the bigger problem is that solvents dissolve the fatty
myelin around your nerve cells. Myelin acts as
electrical insulation for your nerves and brain, and
when this stuff dissolves your brain can
short-circuit. You wouldn't melt the insulation
on the wiring in your car, would you? Don't do it to
If you spray finish indoors,
wear an organic vapor respirator. I bought one for
about 40 bucks at Home Depot. These things use activated
charcoal filters to absorb all the volatile organic
compounds that pass through them. Eventually they get
plugged up and the filters need to be replaced. I store
my respirator in a sealed Ziploc bag when not in use.
Overspray: Even with an
HVLP (High Volume Low Pressure) spray gun, there is
still plenty of overspray. If spraying indoors,
the overspray can cover large portions of your work
area. If spraying outdoors, the overspray can
fall on cars parked nearby. If you cover your neighbor's
house or car with paint overspray, you may be held
liable for damages. Sometimes overspray wipes off like
dust, but sometimes it sticks really well. Watch the
direction of the breeze, and observe how far the
overspray is travelling.