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Dealing with overspray - WaterlooMarc - 01-10-2017
I have finally joined the world of spray finishing and picked up a Fuji Q4 for what I thought was a pretty good price. I did my first project in a garage bay with plastic drop clothes hanging from the garage door hardware and what apparently were too small boxes underneath the legs (painted my floor). Needless to say I was amazed by the amount of overspray floating about with just a simple fan blowing outside so I moved to the driveway for the second coat. This isn't going to be a good longterm solution for me. So I'm thinking of building a spray booth.
I've seen the plans around for a knockdown booth and besides the scale I think one of these will work for me. Although Im not sure what product they are referring to by 'insulation board'. My problem is that I would like to be able to spray in the shop, not the garage. But I only have one window in there so exhausting is an issue. So my question is this: so long as I stick to just water based finishes can I build a booth with sufficient filters and CFM's to simply mechanically catch the overspray? Basically build a spray booth as normal but with the fan exhausting to the shop rather than the outside?
Is this a furiously stupid idea? New to all this...
RE: Dealing with overspray - jteneyck - 01-10-2017
Mark, not a stupid idea at all. I use my DC fan as the exhaust from my temporary spray booth, which is nothing more than plastic hung from the ceiling joists and paper on the floor. 10 minutes to put up/take down, and takes up almost no storage space. The DC fan only has about 1200 cfm yet I have no over spray problems even though my booth is about 8' wide. The key to dealing with over spray, besides getting your gun dialed in to minimize bounce back, is to spray start as far away from the exhaust inlet as possible and spray towards it so that the over spray doesn't fall on what you've already sprayed.
With my setup I use no filters; the over spray goes thru the fan and out the window so there's nothing to ever clog or blind. If you want to return the exhaust air to your shop you will have no choice but to put filters in the outlet air to trap the over spray. Of course, they will plug up and you will have to change them, which can happen surprisingly quickly unless you have a huge bank of them. This was the primary reason I decided to vent my exhaust outside - no filters required. I can and do often spray for an hour and the temp. in my shop doesn't fall off appreciable even in the dead of Winter. If you do elect to vent the exhaust outside make sure you allow for make up air. I have to open an upstairs window and let the air come down my cellar stairs, but that's much better than pulling air down the chimney. Just think it through and it will be fine.
In any case, you can safely spray WB and shellac indoors with a very simple setup. And of course you need to wear a good respirator with organics filters, too.
John
RE: Dealing with overspray - WaterlooMarc - 01-10-2017
Thanks for the insight. My dust collection is piped in so i can't just exhaust it outside although that's a great idea. Of course it may pay just to go grab a cheap HF dust collector just for the blower...
I'm definitely still in the early stages of adjusting the gun. I was more focused on just trying to get a smooth consistent coat laid down. I probably overdid it with the fluid but better safe than sorry.
RE: Dealing with overspray - Joel H. - 01-11-2017
Marc, can't help you on the other part, but I'd go just the opposite on the heaviness of the spray. When spraying, lighter is better. Then you can always spray another coat. you'll find with spraying you use about 1/2 the amount of finish as wiping and have a much more even coverage.
I'm not a pro, and there are lots here that have much more experience, but that's my finding
Joel
RE: Dealing with overspray - jteneyck - 01-11-2017
My DC is piped, too. I use a convenient 5" drop hose as the inlet to the fan. My DC has a hose between the fan and bags. I remove that hose to bypass the bags and replace it with another hose from the fan outlet to the window. I get a little "slag" around the inlet of the drop hose but it just flakes off. I've never had any build up on the fan or housing. WB and shellac are dry before they go very far.
John
RE: Dealing with overspray - fredhargis - 01-11-2017
(01-11-2017, 09:57 AM)jteneyck Wrote: WB and shellac are dry before they go very far.
John
True, that! I don't have a fan, just the curtains and when using waterbornes they wind up as a white dust on the floor that gets swept up. Can't say I've seen that with shellac but I'm sure that happens with it as well. That said, my next shop will have a way to use a fan to evacuate the fumes/overspray/etc.
RE: Dealing with overspray - Cooler - 01-13-2017
(01-10-2017, 05:09 PM)jteneyck Wrote: Mark, not a stupid idea at all. I use my DC fan as the exhaust from my temporary spray booth, [...]
John
I have raised this point in the past. I think exhaust fans are a bad idea for spray booths. It will exhaust the fumes but it will suck in the dust.
A better solution is to blow filtered air into the room. A simple 20" x 20" furnace filter attached to a box fan will move a lot of air into the space. It has the further advantage of keeping a space enclosed with plastic sheet "inflated".
If you are spraying volatile materials it will blow the material away from the motor and not suck it towards the motor.
I have built three darkrooms over the years. Photographic darkrooms are another room that hates dust; hates it more even than a spray booth. My darkrooms had filtered forced air into the room which I turned on before I opened the door to the room. With the blower going opening the door did not suck any dust into the room.
This is not something I invented. "Clean room" technology is built entirely on the idea of filtered positive atmosphere. It is a very effective way to deal with dust.
https://en.wikipedia.org/wiki/Cleanroom
RE: Dealing with overspray - jteneyck - 01-13-2017
(01-13-2017, 08:39 AM)Cooler Wrote: I have raised this point in the past. I think exhaust fans are a bad idea for spray booths. It will exhaust the fumes but it will suck in the dust.
A better solution is to blow filtered air into the room. A simple 20" x 20" furnace filter attached to a box fan will move a lot of air into the space. It has the further advantage of keeping a space enclosed with plastic sheet "inflated".
If you are spraying volatile materials it will blow the material away from the motor and not suck it towards the motor.
I have built three darkrooms over the years. Photographic darkrooms are another room that hates dust; hates it more even than a spray booth. My darkrooms had filtered forced air into the room which I turned on before I opened the door to the room. With the blower going opening the door did not suck any dust into the room.
This is not something I invented. "Clean room" technology is built entirely on the idea of filtered positive atmosphere. It is a very effective way to deal with dust.
https://en.wikipedia.org/wiki/Cleanroom
That approach is all good except you need to have a sealed room for it to work. That's pretty hard to do unless you build a complete enclosure, and once you do that it is unlikely to be something that is easily stored. I've never had dust problems with my open spray booth that is exhausted to the outside. The air velocity is too low for dust to be drawn into it.
John
RE: Dealing with overspray - Cooler - 01-13-2017
(01-13-2017, 09:18 AM)jteneyck Wrote: That approach is all good except you need to have a sealed room for it to work. That's pretty hard to do unless you build a complete enclosure, and once you do that it is unlikely to be something that is easily stored. I've never had dust problems with my open spray booth that is exhausted to the outside. The air velocity is too low for dust to be drawn into it.
John
As I've grown older I am drawn to making smaller items. That allows me to use my old darkroom as a "paint booth". It is just 12' x 8' and has a counter, but for small items it works. I use the old filtered air system of the darkroom for the spray booth. I even have a vacuum hose that snakes into the room through a wall so that the vac sits outside the room when I clean it. It is not nearly as important with finishing as it was with printing photos.
RE: Dealing with overspray - Snipe Hunter - 01-17-2017
Sometimes I sound like a broken record.
Spray outside.
I do it 12 months a year and I do it for a living. Even with rain, hail, sleet and snow, I have fewer problems outside than I do inside. Some days I just can't spray so I get a day off.
I think most people's problems with outdoor spraying is that it doesn't make sense to them. It doesn't have to make sense.