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Building a Downdraft Table for Painting

Posted July 11, 2011 9:00 AM by frankd20

Amongst other things, my sister is a painter. She doesn't paint with brushes, but instead uses spray paint. It's an art form that has been around for a while and is typically seen at tourist locations.

The problem with spray paint is that it tends to pollute the air around where the artist is painting with a mist of paint and propellant. This mist is both bad for my sister and the people watching her work. My sister can wear a mask, but that still leaves it unpleasant for the other folks.

I decided to help her out by making a downdraft table for sucking the mist away as she paints. I wanted to keep the design compact, cheap, and easy-to-operate.

Acquiring a Filter

I started by looking for a filter to use. The idea was to use a simple home air filter that would capture most of the paint mist and vent the exhaust elsewhere for anything the filter didn't capture. I wanted to put the filter in the unit so she didn't need a separate one, so I designed the dimensions of the unit based on the filter I could find.

Unfortunately, I could not find a large filter that was as cheap as I'd wanted, but I did find that two placed side-by-side would work well. With my filters in hand, I set about building a box that would hold them.

Boxing It In

Using plywood scraps from an old sliding door I'd removed during a home renovation project, I constructed a simple box for the two filters to fit in side-by-side and made a good seal.

After the box was complete, I looked for a fan to use. I wanted something that would have a good draw and could output to a vent. I had a blower from the vent hood of an oven leftover from some kitchen renovations, which I installed in the box with a vent to a port on the side of the box. I used a simple frame to hold the filters in place, and also wired in a switch and a cord for powering the blower.

Finishing Touches

The painting surface had to fit on top of the filters and have holes in it to draw in the fumes. I cut a piece of plywood that would fit in, and then drilled a bunch of holes around the perimeter to capture the paint. I first thought about drilling holes all over the table part, but after putting a painting on it to determine the size, I felt it would give her a smoother surface to paint on if the holes were just on the perimeter.

After it was all together, I gave it a quick test. It seemed to draw the paint in quite well, and the filter under the holes did indeed have paint on it. I gave the unit to my sister and she has been using it ever since.

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#1

Re: Building a Downdraft Table for Painting

07/11/2011 9:48 AM

I my girlfriend youngest daughter is an artist going to college. She wanted to get into graphic design, but her mother said, if I paying for her college, you go and major in something that you can get a job. Shes going into her third year as undeclared.

Anyways, I bought her a airbrush kit for Christmas, I was thinking of something simular. I didn't think it was going to be much of a problem.

Question I have: Does the air current have much effect?

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#4
In reply to #1

Re: Building a Downdraft Table for Painting

07/11/2011 10:27 AM

I am not sure I understand your question, but when I tested it with spray paint I could clearly see the paint getting pulled down and into the holes on the table. Without the unit on the mist just hovered above the unit for a while, so it did make a difference.

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#5
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Re: Building a Downdraft Table for Painting

07/11/2011 6:28 PM

I was talking more of the depositing of the paint on the picture.

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#2

Re: Building a Downdraft Table for Painting

07/11/2011 9:59 AM

Have suggestion you may want to attach a hose to the output to move the fumes farther away from where she works. Though the filter is removing the solids the fumes it is dumping back out at her feet. Or a bed of charcoal to remove them.

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#3
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Re: Building a Downdraft Table for Painting

07/11/2011 10:22 AM

I agree, which is why the output goes to something that a hose could be connected to. I left that part up to her, I put in the filters to get the solids more to protect the blower from paint accumulation. The main idea was always to go to a vent hose to put the fumes somewhere else.

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#6

Re: Building a Downdraft Table for Painting

07/11/2011 11:46 PM

Is there risk with this design, which sends the vapors past the spark of the fan motor, of fire or explosion? If not, why not? If this is a risk, what would be the best way to avoid it?

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#8
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Re: Building a Downdraft Table for Painting

07/12/2011 10:50 AM

The blower motor is an induction type which does not create sparks.

The blower is designed for an overhead vent for a kitchen oven. I would think the risk of igniting an oil mist or smoke from cooking would be just as high and is designed accordingly.

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#7

Re: Building a Downdraft Table for Painting

07/12/2011 10:21 AM

I would substitute a couple of those square hole grilles you see for office over-head lighting to hold the canvas off of the filters.

Nice little project, makes someone's life a little better. What else could an engineer ask for?

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#10
In reply to #7

Re: Building a Downdraft Table for Painting

07/13/2011 8:58 AM

I agree. Overspray is a huge problem with spray cans and will kill these filters very quickly.

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#11
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Re: Building a Downdraft Table for Painting

07/13/2011 2:19 PM

I agree that the filters will get clogged frequently as would most filters, a big part of my choice of filters was cost and availability for that reason. I did this project about a year ago and just got to posting it now, but if I recall the filters came in a 4 pack and were in the $5 range for the pack. Since you use two filters at once that gives you two sets of filters, but still not bad for the added safety.

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#13
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Re: Building a Downdraft Table for Painting

07/15/2011 3:18 PM

I consulted my sister about the use of the square grilles you reference as I do think it would be easier than making a board with holes in it as I did. In addition to spraying paint on, she uses a tool to scrape paint off in various places. So while I think the plastic grille could be used, it would need a flat board under the painting so the grid pattern didn't come through.

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#9

Re: Building a Downdraft Table for Painting

07/12/2011 11:17 AM

In the 90's I took up the airbrush. After just a year, I started wearing a cannister mask. I started reading airbrush magizines and found they have similar tables (hoods). I was working inside a garage at first, then I got a filter hood and took painting indoors. In about my third or forth year, I had a physical at work and it pointed to kidney problems. A little investigation found it was not a work site problem, but a hobby causing the problem. I was trying very careful with the over draft of my paints. The problem was I turned off my hood fans when using the solvents. be aware of the solvent fumes !

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#12

Re: Building a Downdraft Table for Painting

07/14/2011 4:37 AM

Cool project. I hate spray cans myself, but if you have to or want to use them, then that downdraft box is a great idea .
Del

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