Paint Spray Booths

[Robert Porter]

I don't like using a respirator, I find them horribly uncomfortable for more than a few minutes (and I typically airbrush for anything from 1 to 3 hours at a time) and I have a beard, face mask respirators don't seal properly on a beard so their effectiveness is limited. You also have to consider that your eyes are capable of absorbing fumes, if you're using something dangerous enough to use a respirator you should often also wear eye protection.

I also can't deal with fumes. I spray acrylics, lacquers and enamels. Acrylics bother me the least, enamels the most, lacquers are terrible if I huff them but the good thing about lacquers is the fumes are short lived, they cook off quickly where as enamels the model keeps releasing fumes for ages and I have to put them model in a separate unused room for a day or two while it's letting off fumes. I thin Tamiya acrylics with lacquer thinner anyway, so that's basically the same as spraying lacquers.

My technique is just to get fumes away from me.

I actually just use a cardboard box with a reasonably powerful desk fan as a vent.

I haven't burned my house down yet in spite of spraying pure lacquer, enamel and acrylic thinners directly in to the fan at 40-50psi, lol. I tested it before setting it up, trying my best to get the right ratio of fumes to air and I couldn't start a fire, not sure what sort of motor it has but thus far it's been pretty safe.

I honestly believe some of the caution is overhyped. I was able to generate a flame not an explosion by spraying directly into the motor of a box fan outside. Its an old much abused fan.

I recently visited a friend that makes and paints model figures for several different games. He uses the setup here: Jet.com - Prices Drop As You Shop

This one is advertised all over the place and several folks here have mentioned it. We took it outside, setup his airbrush to shoot at 30PSI and blew 2 full bowls of enamel thinner through it. Nothing, no flames, no bangs! Hardly scientific testing but I feel much more comfortable with something like that now.

I also don't particularly enjoy using a respirator but I do, I have a goatee not full beard but it does get in the way sometimes. And I have to agree about enamels in general. I have been diligently switching my paint collection to acrylics which as you mentioned are easier on the eyes and in general much less of a mess.

If I go silent on the board you will all know I figured out a combination to blow myself up! But honestly I think it will work out just fine.

 

[WolfRacer]

Yeah I guess it's important to know the risks. I don't have any flammable ducting downstream of my fan so I'm hoping if the fumes do one day ignite I can just stop spraying and hopefully the fire just goes out with no fuel to feed it, though maybe the fan itself might catch on fire in which case I'll throw it out the window and grab the garden hose

I'm not too worried about an actual explosion because the whole purpose of the fan is to keep the concentration of fumes in the room itself as low as possible.

I had considered hacking the fan apart and making a simple belt drive to get the motor out of the fan it self, but the airflow of the fan helps cool the motor so it's probably even more dangerous. At work we have some epic massive belt driven fans but they require an additional fan for the purpose of cooling.

Maybe you could cordon off a portion of the fan so it draws air from the room to cool the motor, while the rest of the fan draws air from the spray booth.

I mention the eyes because I've heard of some people who spray without an exhaust and just trust their respirator. It's probably fine if you're only spraying small stuff, but a mate of mine was spraying yellow primer on something with ~1m wingspan and his exhaust fan broke but he kept spraying anyway wearing a respirator. At the end of the session he was complaining his eyes were hurting and things looked cloudy, I had a look and they literally had a yellow tinge to them in spite of him wearing safety glasses (but not the sort he should have been wearing!), I can't imagine the solvents were good for him. Obviously that's an extreme situation but after that it's something I try and keep in mind.

 

[Robert Porter]

Yeah I guess it's important to know the risks. I don't have any flammable ducting downstream of my fan so I'm hoping if the fumes do one day ignite I can just stop spraying and hopefully the fire just goes out with no fuel to feed it, though maybe the fan itself might catch on fire in which case I'll throw it out the window and grab the garden hose

I'm not too worried about an actual explosion because the whole purpose of the fan is to keep the concentration of fumes in the room itself as low as possible.

I had considered hacking the fan apart and making a simple belt drive to get the motor out of the fan it self, but the airflow of the fan helps cool the motor so it's probably even more dangerous. At work we have some epic massive belt driven fans but they require an additional fan for the purpose of cooling.

Maybe you could cordon off a portion of the fan so it draws air from the room to cool the motor, while the rest of the fan draws air from the spray booth.

I mention the eyes because I've heard of some people who spray without an exhaust and just trust their respirator. It's probably fine if you're only spraying small stuff, but a mate of mine was spraying yellow primer on something with ~1m wingspan and his exhaust fan broke but he kept spraying anyway wearing a respirator. At the end of the session he was complaining his eyes were hurting and things looked cloudy, I had a look and they literally had a yellow tinge to them in spite of him wearing safety glasses (but not the sort he should have been wearing!), I can't imagine the solvents were good for him. Obviously that's an extreme situation but after that it's something I try and keep in mind.

I remember hearing something similar about the eyes being a commonly overlooked source of absorption. When I worked at Glaxo, big pharma, and had to go to the server room in one of the labs, we were required to wear full face respirators when certain operations were under way. They were uncomfortable and hot and mine kept fogging up at the worst time, but the reason I am sure was to protect our eyes from the fumes.

Like you mentioned I believe the dangers are real but unlikely to result in an explosion. I mean they sell thousands of these type spray booths and I can't honestly recall a news story about anyone blowing themselves up using one. Although I laugh at the illustrations which always show the exhaust vent pointed right back at the operator! Hopefully no one is foolish enough to think thats a good idea!

 

[mikewint]

If the fan/blower has brushes (electrical ones not paint) then you have an open spark, BUT, ignition is a matter of fuel/air mixtures ratios. Dilute or rich mixtures will not ignite. Fill a room with pure hydrogen and make all the sparks you want, without oxygen nothing will happen. So small amounts of solvent to air mixtures are not going to ignite.
IMHO, for the small amount of enamel or lacquer sprayed by the average modeler it is not worth the expense of a commercial-type booth. A simple box and a fan/vacuum is sufficient with a hose leading to a open window works just fine.
Now chemical allergies to the various solvents are a different problem altogether. Various individuals can react to extremely small concentrations of solvents and/or particles of overspray that escape into the air. Those individuals may need respirators and fume hood type booths to safely spray even small amounts of any type paint even acrylics.
Again, personally, I spray acrylics. I use an old cardboard box about 2ft x 2ft x 3ft and seldom use the vacuum. Now when I built the 1/48 B-29 I used the vacuum quite a bit as I sprayed quite a bit of metallic aluminium paint.

 

[Robert Porter]

If the fan/blower has brushes (electrical ones not paint) then you have an open spark, BUT, ignition is a matter of fuel/air mixtures ratios. Dilute or rich mixtures will not ignite. Fill a room with pure hydrogen and make all the sparks you want, without oxygen nothing will happen. So small amounts of solvent to air mixtures are not going to ignite.
IMHO, for the small amount of enamel or lacquer sprayed by the average modeler it is not worth the expense of a commercial-type booth. A simple box and a fan/vacuum is sufficient with a hose leading to a open window works just fine.
Now chemical allergies to the various solvents are a different problem altogether. Various individuals can react to extremely small concentrations of solvents and/or particles of overspray that escape into the air. Those individuals may need respirators and fume hood type booths to safely spray even small amounts of any type paint even acrylics.
Again, personally, I spray acrylics. I use an old cardboard box about 2ft x 2ft x 3ft and seldom use the vacuum. Now when I built the 1/48 B-29 I used the vacuum quite a bit as I sprayed quite a bit of metallic aluminium paint.

I truly think you are correct, and no one in the house has exhibited allergies, I get light headed pretty quickly spraying enamels or even brush painting with them so I do use a respirator. But I am convinced that I will be perfectly safe with my low end spray booth. Like you said I would need a pretty good mixture to put myself at risk. Don't think thats going to happen. Heck I know a guy that sprays acrylics in his kitchen into a box with no vent and just the windows open and he is still kicking!

 

[mikewint]

I don't spray in the kitchen, I have a basement work room but 95% of the time I spray acrylics thinned with Tamyia's thinner without any type of vent. With one exception. I use Tamiya's lacquer thinner to thin for bigger paint jobs. The difference between it and isopropyl or denatured alcohol is, in my opinion, night and day. It's more forgiving and, once you get your mix, pressure and distance figured out, it goes down ridiculously smooth.
I've also read that Tamiya's thinner has a wetting agent of some sort in it