Paint Spray Booths

[Robert Porter]

I am sure this topic has been done to death, I did search the forums but did not see my particular questions answered so I am going to give it a go here.

First in an effort to save some money I would like to make my own. I anticipate using a 20x20x1 furnace filter for catching particulates. Not being an engineer I need some guidance on how powerful a fan I need to suck air through say a 4 - 5 inch round duct and the filter and still be effective. Fans seem to be rated in CFM so is there a magic minimum I should be looking for?

The duct run will be about 10 foot long at maximum. (I live in a condo and will be venting out of a window.) However this could be reduced considerably if necessary.

Second I have seen in various forums and threads a lot of debate over brushless motors vs regular motors such as those used in range exhausts and bathroom vents. The issue appears to be the risk of fire/explosion when using flammable fluids especially when they have been aerosolized via an airbrush.

My own experience spraying thinner at 30psi through a box fan resulted in a momentary flamethrower so I know the risk is real, this was even outside. I just wanted the fumes as far away as I could even when wearing a respirator. Obviously not something I am looking to repeat indoors.

So with all that being said, any advice, caveats, general do's and don'ts? I am okay with building the box and any minor metal work for attaching the duct work to the fan etc.

 

[Wurger]

There is a difference in airbrushing at an area of 10 square centimeters of a model or 10 square meters of a car. So...if you aren't going to paint your car with an airbrush, the cheapest way to prevent aginst the fire/explosion is :

1.Stop smoking while airbrushing.
2. Don't use the spray next to a naked flame or any incandescent material.
3. Don't spray at any electric device being working directly.
4. Keep a window open.

There is no need to use any spary booths IMHO.

 

[fubar57]

I believe 450cfm is a number I read years ago in Fine Scale Modeler. Also the exhaust fan should have an external motor to prevent possible explosion using lacquer or enamel based paints

 

[Robert Porter]

There is a difference in airbrushing at an area of 10 square centimeters of a model or 10 square meters of a car. So...if you aren't going to paint your car with an airbrush, the cheapest way to prevent aginst the fire/explosion is :

1.Stop smoking while airbrushing.
2. Don't use the spray next to a naked flame or any incandescent material.
3. Don't spray at any electric device being working directly.
4. Keep a window open.

There is no need to use any spary booths IMHO.

I understand what your saying but even with a window open, 5 minutes of spraying the fumes permeate the entire condo and as I am not the only one home not everyone wants to wear a respirator plus the wife complains it affects her cooking! So in my case its outside or a good working spray booth.

 

[Robert Porter]

I believe 450cfm is a number I read years ago in Fine Scale Modeler. Also the exhaust fan should have an external motor to prevent possible explosion using lacquer or enamel based paints

There are a number of fans that have a separate motor so that is indeed what I am looking at. I believe a lot of them go by the common name of "squirrel cage" fans. 450 sounds reasonable. My range exhaust fan is rated at 100 CFM and does not do a very good job even with a clean filter of exhausting the cooktop. I will post back here with my actual selections and see if they pass muster or possibly help someone else.

 

[Robert Porter]

I believe 450cfm is a number I read years ago in Fine Scale Modeler. Also the exhaust fan should have an external motor to prevent possible explosion using lacquer or enamel based paints

Found this thread at FineScale, very informative, possibly the one you were referring to?

DIY vs. Commercial Spray Booth? - FineScale Modeler - Essential magazine for scale model builders, model kit reviews, how-to scale modeling, and scale modeling products

 

[Wurger]

I understand what your saying but even with a window open, 5 minutes of spraying the fumes permeate the entire condo and as I am not the only one home not everyone wants to wear a respirator plus the wife complains it affects her cooking! So in my case its outside or a good working spray booth.

I've grasped. However I airbrused a couple of models at my room that isn't too large and there have never been any trouble with fumes. So either you use too huge air pressure and too much of too thinned paint or the airbrush nozzle is of too large diameter. Also the distance you apply your paint from can be incorrect.

 

[Robert Porter]

I've grasped. However I airbrused a couple of models at my room that isn't too large and there have never been any trouble with fumes. So either you use too huge air pressure and too much of too thinned paint or the airbrush nozzle is of too large diameter. Also the distance you apply your paint from can be incorrect.

Quite possible on all accounts, I have setup for another trial run with a window open and a box fan behind me so will see if that works. The issue is usually just with enamels, acrylics have not been a problem yet.

 

[Wurger]

I see. I've been using enamels for years and mostly but didn't find them troublesome.

 

[Builder 2010]

This thread has come at a very apropos time. I'm contemplating doing the same thing. Unlike Wurger, when I spray solvents in the basement, the HVAC system picks up the odor and sends it all through the house to the discomfort of my wife. Even when spraying water-based paint, I don't like breathing in all the fumes. After spraying the B-17 Vallejo aluminum, when I blew my nose later in the day, it was all aluminum dust. That can't be good. That being said, my wife is having a problem with cutting a hole in the basement wall for the 4" dryer vent. I'm still lobbying to get past this impediment.

Which brings me to the same question that Robert has; make or buy. I kind of like the idea of a brushless motor with speed control. No commutator = no sparks = no ignition source. Pace Industries has a nice 36" unit with lights, extra outlets and fully wired ready to go, but it's pricy (over $400 not including installing the outside vent). My grandson (very smart) suggested cobbling together a frame out of PVC pipe and covering it plastic sheeting and using a square box fan with the filter attached. I've also designed a MDF version, again using furnace filters in a slot, but can't decide on the motor/fan combination.

So I need technical and moral support.

 

[fubar57]

One thing you didn't bring up but touch on is a respirator....

 

[Robert Porter]

One thing you didn't bring up but touch on is a respirator....

View attachment 356548

Agreed, I do use one, even when working outside both for brush and airbrush when using Enamels. I skip it when brush painting with Acrylics but always use it with Enamels. My wife has a phone video of the one time I brush painted with enamels inside without one and after an hour I slowly tilted sideways and took a nap.

In all honesty there is no good reason not to use one, especially while using an airbrush. It is annoying but my health is worth more than a little discomfort. Hence this whole thread. While I was the only one affected to that degree the smell was pervasive in the entire condo which is of course a source of contention.

My takeaways from this thread and my research are as follows, please anyone feel free to chime in if you can add or correct my thoughts.

1. MUST be vented outside (an open window by itself is not sufficient in most cases).
2. Needs to be a sufficiently strong fan/motor to provide an airflow of @400 CFM for a booth size of 24X24 inches in height and width. Take into account length of duct work, filters etc. Bends in the duct work should be avoided if possible.
3. The filters should be sufficient to remove particulate but you don't need or want HEPA level filters. A standard furnace filter should suffice.
4. Air flow should be routed in such a manner as to avoid the exhaust air stream from flowing over the motor itself. Separate motor from fan needed.

Other than these factors everything else seems open for individual wants and tastes. My research into fans/motors indicates that cost can be anywhere from @200USD to OMG! But some searching on craigslist yielded a number of sources for less. But pay attention to the CFM rating. One fellow I know uses an old squirrel cage fan from an 1960's era oil fired furnace. Its quiet but rather large and the plumbing as it were was all hand built.

But to fubar57's point, a booth does not remove the need for a respirator. And the little cloth or paper masks you see all over the place will not provide sufficient filtering you need a real respirator. Locally here Harbor Freight sells a nice one for @20USD.

 

[Robert Porter]

Recently in all my research I came across this warning on every single one of the available Hobby Spray booths. For an example follow the link below and scroll down to the product details. They all vary a little but essentially say

• Note: Not intended for use with Hazardous Materials, Flammable or Explosive Paints or Materials

Unfortunately that describes all enamels, lacquers and some other paint types used in modeling.

Link to example: Portable Hobby Airbrush Paint Spray Booth Kit Exhaust Filter Extractor Set Model | eBay

This is ridiculous! The name and rest of the description makes no mention of what paints it is safe to use it with.

 

[fubar57]

I'm going to assume it's to do with the motor type. Here's a few other places you can check out

MicroMake Ultimate Airbrush Outfit

Pace Enterprises

SPRAY-BOOTH

 

[Robert Porter]

I'm going to assume it's to do with the motor type. Here's a few other places you can check out

MicroMake Ultimate Airbrush Outfit

Pace Enterprises

SPRAY-BOOTH

That is exactly what it is, when the price is under $150 it has the cautionary statement. As soon as you clear the $300 mark the warning statement goes away. Which is what I find with all the DIY stuff as well. I can buy motors all day long below 100 but they all have the "explosion risk" warnings. Once you get above the 200 mark for motors that mostly drops off. Either because it is a brushless motor, or as discussed above the motor is removed from the airstream.

I just think its a shame manufacturers are not more clear about it. The first link you sent is the EXACT same booth I was looking at for $90,00 but the link you sent was for $300.00+ when I read the specs on both it was the motor that was different. The booth itself was the same.

Of course those cheaper booths sell all the time and we don't read about modelers burning their house down very much so I know its relatively safe either way. Its just with my luck I will be the exception that proves the rule.

 

[fubar57]

And then the headline reads, "Local Meth Lab Blows Up". I'm strictly an acrylic user and everything I've read says acrylic is not flammable so if you go that route you're probably safe with a cheaper model. Mine came from the papermill I used to work in and was used for extracting moisture from pulp samples using an external motor. The power of the fan is really over-kill here, I could probably use it to inflate something the size of the Hindenburg in about 30 seconds. Something not mentioned here is the length of the exhaust hose, the longer the run, the more power needed

 

[Robert Porter]

And then the headline reads, "Local Meth Lab Blows Up". I'm strictly an acrylic user and everything I've read says acrylic is not flammable so if you go that route you're probably safe with a cheaper model. Mine came from the papermill I used to work in and was used for extracting moisture from pulp samples using an external motor. The power of the fan is really over-kill here, I could probably use it to inflate something the size of the Hindenburg in about 30 seconds. Something not mentioned here is the length of the exhaust hose, the longer the run, the more power needed

Thanks! No explosions wanted. And I believe you are right about the acrylics not being flammable. You might want to consider pointing your fan at the border after our recent election, I hear a lot of folks are thinking of heading your way!

This is a little off this topic but I have to ask. I grew up on enamels and have occasionally used acrylics. In particular the Tamiya Acrylics and the Vellejo Airbrush Ready line. I have had reasonably good luck with acrylics and assume my reluctance to switch is pure habit nothing more.

I believe you live in Canada so manufactures may be different but which brands do you find the most useful in Acrylics? I can find enamels in every hobby store but most just don't stock a wide variety of acrylics here. Do you end up buying online or can I use the "Art" acrylics found in every craft store I see?

 

[fubar57]

I'm a 4hr round trip from the nearest hobby store(just got back as a matter of fact. Left a 7:30 this morning) and they are limited to Tamiya, Vallejo acrylics and Humbrol, Testors enamels and they don't restock on a regular basis. Ordering online is sketchy at best, either they won't ship because of a countries laws concerning fluids (some include acrylics) or the shipping costs are unreal

 

[mikewint]

I've never had a problem with smell and acrylics but a simple and cheap solution for models is a cardboard box and a small wet/dry vacuum cleaner with an exhaust port so it can be used as a blower. Vacuum hose to box and a second hose from the exhaust port to a open window. Overspray will get into the vacuum but all have a foam filter or paper-bag filter. Used this system years ago with the old balsa wood - rice paper - dope flying models
As to enamels I use and prefer the Testors line either the 1/4oz for basic colors or the Model Master line for more "official" colors

 

[WolfRacer]

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.