Spray booth exhaust fan - water based only

[BTWILL864]

I have done multiple searches and bought two books and a video on spray finishing, and I still am not sure I have the right answer, so before I spend more money than I need to, here goes:

I want to spray water based finishes in my garage, and want to build a knock down open-end spray booth to control the overspray. I bought Michael Dresdner's video on spray finishing, and he had a setup using 4x8 pieces of cardboard. He had cut a square hole near the floor on the back panel, and opened his garage door a couple of feet and then place an exhaust fan over the hole. This is EXACTLY what I am looking to do. I plan to spray water based ONLY, and my question is about the fan.

His looks like about a 24"x24" whole house fan. Its got its own metal "box", and it looks like he has attached plywood to the top and bottom and maybe some chicken wire or something in the front to hold some blue filter fabric. I'm pretty sure its a house fan because it has the shutters on the back. Okay, so I have found a similar fan at Lowes for $149, and the filter fabric, but...

Is the fan to big? I believe it will move around 2000 cfm. I have a 20x20 garage, but I figure I'm only drafting the air close to my spray enclosure. I have read of people using explosion proof fans and axial turbine fans, but I don't think I need that. I have also heard of people using 16" gable attic fans, which I believe move about 1300 cfm or so, but I would need to build a frame around it. I saw something similar to this used as a dust collection setup in the Taunton Press "Workshops" book. I have also heard of using a regular box fan, I believe it was in American Woodworker, and Dresdner uses one in the video for a benchtop setup for small projects. That is a complicated lead-in, but I wanted to let everyone know I did my research. So, given that I'm not spraying any solvent based lacquers or anything like that, and will probably use it to spray some latex paint most of the time (Porter Cable HVLP conversion gun, 2.2 mm tip, gravity feed, 5 HP 20 gall Campbell Hausfield compressor, already used it to spray cabinets and doors and it seems to work fine, the wife likes the results) does anyone have any tips on what size fan I should get? The difference between the house fan and the largest attic fan I would buy is about $75, so its a fairly big deal, but I also want to make sure I control the fumes and overspray. It will vent to the back of the house away from the neighbors.

Anybody got any ideas or experience? Thanks in advance.

BW

[Larry Jaques]

On 12 Nov 2003 02:26:38 GMT, [e-mail] (BTWILL864) brought forth from the murky depths:

-snip of research-

IANAP, but... I'd try the cheap box fan routine and an HVLP sprayer setup. If it doesn't work well enough, go to a higher volume fan. (Replace fan when it stops working due to gummy residues.)

Make sure you have a good (and direct) flow of air into the "booth" and out the back. And make sure the flow of air is in the proper temperature and humidity ranges for spraying. (There's your Winter "Gotcha!") G'luck.

Sure you wouldn't rather have a nice, hand-rubbed oil finish? (Huh? Huh? Huh?)

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[Ed Angell]

shop. The biggest problem is dust that comes from the surrounding room. Most of the painters cleaned the work area fairly well and wet down the floor to keep dust from being drawn into the spray area and on to the work.

Ed Angell

[Terry Jensen]

BW, I am also looking for some replies to your post. Basically, what works?

However, you may want to consider spraying more than water based. Shellac forms an excellent barrier coat that will allow you to use water based dye (or oil based stain) under a water based finish. Terry