Spray booth questions...

Since you're going to be painting in a garage, why not just rig up a plastic sheet with a zipper and seal off your hobby area from the cars? The zippers are available at most hardware stores and will keep any particulates from reaching the car. Then you only have to worry about breathing in the fumes, and a respirator will take care of that. You probably don't even have to go that far, as airbrushes don't pump out the CFM that would move paint mist far enough to adhere to a car. The paint hardens long before it would travel even 4'. I sometimes have issues with paint drying too fast at 6"!

The spray booths you refer to are more suited to an in-house requirement. As you are in the garage, and well removed from the main living areas, you don't have the same issues that many of us deal with, so why put out the money? You can buy a LOT of kits or paint for the cost of a small spray booth!

A couple issues besides getting paint dust and overspray on your cars...what about dust from your garage on your model as you are painting. Regulating humidity and temperature (depending on climate location) as well as fumes.

You don't need duct work, IF you pump it right out through the wall. Ducting is mostly necessary because of location of the booth itself and the spot most feasible to dump out the vapors to the outside.

Here is a resource for making an inexpensive paint booth. You can also use a box fan mounted in a window instead of having a dedicated exhaust fan. Or even use your SHOP VAC to act as a exhaust system. Here are a couple illustrations you might find useful.

While I have a flange on the outside of my homemade booth, I often do not have a duct/hose hooked up. I also primarily want it for avoiding overspray in the rest of the shop, and to cut down odorl.  Yes, it cuts down oder even without an outside vent (though it is better with the vent hooked up)  The booth is right next to a window and I have a simple piece of wood with a hole in it and another dryer hose flange over that hole.  The piece of wood goes in the bottom of the window opening (full width) and the window lowers down to clamp the wood in place.

You want a good sized fan (greater than 100 CFM) because the filter offers resistance that cuts down the CFM especially when it gets some paint on it.

The booth includes muffin fan, a furnace filter, and a top mounted liglht that shines into the booth.  An article on its construction was in an old issue of Ships in Scale if you have any access to that magazine.  The body was made from 3/8 and 1/2 inch particle board.

Bgrigg

You probably don't even have to go that far, as airbrushes don't pump out the CFM that would move paint mist far enough to adhere to a car. The paint hardens long before it would travel even 4'. I sometimes have issues with paint drying too fast at 6"!

Excellent point! 

When I was growing up I built models in my parents' garage all the time with no issues whatsoever. And that was without a cleaning station, a spray booth of any kind, etc. Now, I did have issues with overspray and paint fog the last few times I built, but that was in an indoor environment after my parents moved.

Think I may have to run a few tests once I get the workspace a bit more cleared away...

HawkeyeHobbies

A couple issues besides getting paint dust and overspray on your cars...what about dust from your garage on your model as you are painting. Regulating humidity and temperature (depending on climate location) as well as fumes.

Regarding dust, I'm planning to get the garage as clean as I can and keep it vacuumed and swept regularly. When not actively painting, I'm planning to cover the models to keep dust away. Not ideal, but it is what it is.

Regarding humidity and temperature...we have plenty of both here in Austin, especially during the summer. Not much I can really do about it except wait until things start to taper off a bit. And before anybody suggests moving the show indoors, I've got a very inquisitive two-year-old in the house, so apart from maybe decal work, the modelling and all the harsh chemicals and small plastic bits are staying outside.

You don't need duct work, IF you pump it right out through the wall. 

Here is a resource for making an inexpensive paint booth. You can also use a box fan mounted in a window instead of having a dedicated exhaust fan. Or even use your SHOP VAC to act as a exhaust system.

That's just the thing. I'm basically up right up against a 40-ft section of wall. No dryer vent to tap, no windows. Just drywall, framing, insulation and then brickwork (which I'd rather not cut through). 

Though I have to say, I'm really digging the Shop Vac idea! I saw a DIY booth someone built out of one of those big, clear plastic bins, and with a little modification and a plenum on the back that might be just what I need...

DoogsATX

That's just the thing. I'm basically up right up against a 40-ft section of wall. No dryer vent to tap, no windows. Just drywall, framing, insulation and then brickwork (which I'd rather not cut through). 

Though I have to say, I'm really digging the Shop Vac idea! I saw a DIY booth someone built out of one of those big, clear plastic bins, and with a little modification and a plenum on the back that might be just what I need...

 

The shop vac idea is a pretty good one and there are a couple issues to think about.  I've had a chance to measure duct velocities at the face of the hoses for these things.   Many--if not most--have been in the 5,000 fpm range, which is considerable.  Simply cutting a hole and sticking the bare end of the hose inside a box is not the brightest thing to do.  In that configuration, all the air is directed toward the hose.  That includes the air and paint coming out of your airbrush or spray can.  In addition, there will be "dead" areas airflow-wise where capture simply will not occur. 

Your idea of a plenum is good, but I would suggest the addition of a baffle placed in front of your hose to help even out the airflow.  The baffle distance from the back of the hood should be 0.75 times the diamater of your hose or ducting (for a solid baffle).  The baffle area should be 0.60 times the area of your hood (width x height). 

The hood should also be deep enough to create linear airflow and provide adequate capture.  Many plastic boxes aren't deep enough to do that.  What I'm giving you is ideal, but it gives you something to use as a base (if you want).

Hood width should equal your work size + 12 inches.

Hood height should equal your work size + 12 inches.

The distance from the front of the baffle to the face (front) of the hood should be 0.75 times the height or width of the booth, whichever is greater.

Lastly, the positive pressure side of the vacuum needs to be far, far, away; not because of vapor concentrations (that will be solved through dilution ventilation), but because all that airflow is going to stir up dust that you couldn't reach in your clean-up efforts, and it will be entrained into your booth where it will be deposited directly onto your model (Murphy says so.)  Get yourself some cheap plastic dryer hose or other similar stuff and connect several feet of it to your vacuum discharge outlet and place the discharge end away from your work space (rafters/ceiling, maybe?). 

Hope this helps.

Gip

Its not hard to cut in and install a dryer vent through a wall. For a handyman its a thirty minute project.

You might want to partition off the modeling area with solid (temporary) walls or a durable heavy curtain. Then you'd be able to run a small room air conditioner to regulate temp and humidity in your workspace. The new a/c units (floor type) with hoses allow you to route outside the work area such as this one.

It takes these units just a few minutes to make even a medium size work area comfortable enough to work in.

When I had my shop in my 2 1/2 car garage, I partitioned off 2/3rds to use as workshop and office area. The temporary walls were made up of pegboard with insulation to keep the winter chill and summers heat and humidity out. The whole thing went up in a day or two and was easily removed and most reused when I took it down.

This pic shows (right side) the wall between my modeling area and the vehicle bay. I was still able to retain and use the 16' wide overhead door. I stepped the wall down below the door so as to not interfere with its operation. Every part of it was assembled using drywall screws.

DoogsATX

 

Bgrigg:

 

You probably don't even have to go that far, as airbrushes don't pump out the CFM that would move paint mist far enough to adhere to a car. The paint hardens long before it would travel even 4'. I sometimes have issues with paint drying too fast at 6"!

 

Excellent point! 

When I was growing up I built models in my parents' garage all the time with no issues whatsoever. And that was without a cleaning station, a spray booth of any kind, etc. Now, I did have issues with overspray and paint fog the last few times I built, but that was in an indoor environment after my parents moved.

I don't even use my spray booth for airbrushing- only for rattle can work. I find so little overspray with an airbrush I just have the setup at my normal assembly bench and very seldom get paint on anything else other than model I am painting.  And after most sessions with airbrush I find little smell compared to when I use a rattle can.

This is what I use and it works for me.  I made a spray booth 3' x 3' x 3' out of plywood.  I mounted an under the counter fl. light under the top, cut a hole in the back and mounted a muffin fan and a flange.  In front I cut an odd remnant of clear lexan or plexiglass 3' wide by about 2' and mounted it by hinges to the top.  Then, set the whole thing on a steel service cart from Harbor Freight.  My compressor sits on the bottom shelf.  I mounted a power strip on the outside where the light, fan & compressor plug in, then an extension cord to power.  When I'm ready to paint I just wheel the whole thing to the open garage door where the overspray and fumes get sucked outside.  When I'm done painting I slip another piece of clear lexan or plexiglass 3' x 1' to cover the gap in the front bottom, clean my air brush, then just roll the portable paint booth to it's place against the wall and you're done.

Hope this helps,

Michael B.. 

Thank you all so much for your thoughts and suggestions! Some really great stuff here. 

At this point I think I really need to pick up some paint and do a few spray tests to determine how much, if any, exhausting power I need. 

Hopefully nothing or a simple box fan + furnace filter will do the trick. I've got a big compressor on the other side of the garage, and the tank can run an airbrush for hours without having to kick in and refill, so it'd be awesome to keep that relative quiet. But if I need an exhaust fan or shop-vac, so be it.

@Hawkeye - blocking off the third bay and bringing in a portable AC unit sounds awesome, but I think at this point it's well beyond the wife acceptance factor. Definitely something to eye over time, though, and maybe try to get in place for next summer.

Managed to do a bit of spray testing last night with some PVC joints I had lying around. 

The good news? Overspray was not a big deal at all. The fumes were actually a bit stronger than I figured they'd be, but nothing a respirator and/or a hint of air movement couldn't fix.

The bad news? Nasty spattery paint.

Blech. I've got a new Iwata HP-C Plus on the way, but I'd been hoping to keep the old Paasche H around for clear coats and the like. Looks like it'll need some new tips and needles...

Give it a good soak in lacquer thinner, and some love and they'll be good as new!