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casethejoint

Modelling Paint Booth

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I finally got around to this last weekend. I have been thinking about making one for ages, mostly so that I can spray larger stuff indoors, in the garage, when it's too wet/too cold. And also for airbrush work which is always in my garage (where the compressor lives).

I've seen a few videos of these on YouTube, and lots of talk about the danger of sparks from bushed motor fans etc. Largely I have dismissed these, as most of what I spray is water-based acrylic and the flammable stuff I spray (mostly rattle can paint and lacquers) simply isn't in a concentrated enough form to explode when not under compression. So worst case scenario it might burn. Which is not a big deal for me and I have a fire extinguisher nearby and handy.

So what kick-started this for me and got me going was I saw this in my local B&Q for £25:-

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... which is the full kit including extractor fan and 3m of hosing, plus a couple of useful fittings for the hosing.

The fan is 20 watts. It sounded too lightweight to me to be effective enough but I figured in any event I'm going to need a baffle/filter box with a 100mm hole in it, some fittings and some hose. So I can always put a more powerful inline fan in later if I want to.

My basic design is a 6mm MDF based box with a 100mm hole in one end and the fan mounted. The filter frame is 2 parts of 6mm MDF with 4 slots cut in them (I did both at once with a jigsaw) that enables me to "sandwich" a filling of filter material in between them. The outside one of the pair is bolted into place with M3 nuts which you can see in the pic below. These will be replaced with wing nuts when they arrive which will make changing the filter easier.

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Currently my filter is a dishcloth ;). Thought I'd at least test that - some proper filter material is on way to me.

This gives you a sense of dimensions:-

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The dishcloth filter clogs up pretty quickly as you can see. This is Ford Tasman Blue I'm painting an F350 tailgate with:-

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I took the vacuum cleaner to the dish cloth filter and found I could clean it out again fairly easily.

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It clogs up even more quickly with lacquer. In fact that pretty much turns it into fibreglass ;)

All that said, it's working surprisingly well. The 20 watt fan is proving a lot more effective than I thought it would and if I'm careful and don't try and paint too fast I can ensure that no overspray ends up in the garage. In theory I can also vent the hosing to the outside to remove fumes etc, but haven't got that far yet.

I can make the unit a little more efficient by sealing a few of the gaps I have and I'll also try the new filter material this weekend if it arrives in time and will let you know how that improves things.

 

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I really like this. Have been thinking of making something similar myself and I really like your design. Let us know what filter material you are using.

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Like that a lot.  I've got my own paint booth in the workshop made from a large plywood workbench and 3 shower curtains that completely surround it, but I definitely need an extractor system.  I've got a snail fan somewhere but I need a proper filter and some more tubing to pump the gasses outside.

It doesn't help that we do a lot of woodwork in the workshop so the whole place is always full of sawdust.  The router in particular makes lots of very fine dust that gets over everything.  I have to mist down the spraying area before I begin to get all the dust away.

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Hi guys,

16 hours ago, njmlondon said:

I really like this. Have been thinking of making something similar myself and I really like your design. Let us know what filter material you are using.

After the dishcloth, my next test will be some 3mm thick activated carbon foam. As far as I've been able to find out, there are three pore sizes for different grades of filtration - the 3mm stuff seems to be "small". I'll let you know how that works out. I might need to try different sizes.

@Mad Ax - if you have height with your design (and so large air volume that the paint is moving around in), I don't think a 20 watt bathroom extractor type fan would cut it for you. With my design (where I've tried to limit volume and also create a funnel effect) it's just on the limit. With my airbrushing it's about perfect. I use mostly acrylics and so I'm painting in the 10-12 PSi range which is pretty light and low paint volume so the fan can keep up quite easy. When I spray a rattle can, which obviously has higher pressure + paint volume I find I am having to spray slightly more slowly to allow the fan to clear the booth out. Maybe 25% slower than normal (eg pauses in between passes).

This may not necessarily be a bad thing - anything that slows you down can have the added benefit of making you concentrate more. Don't know if it'll affect paint finish (I really doubt it) or my natural flow but time will tell.

Also worth noting - I read a lot about how an immediate right angle (like I have in my design) in the ducting can cause turbulence which is not ideal. That's why most commercial booths vent straight out the back. Again, I'll experiment and see if it's a problem. I wanted a side exhaust so that I could get a maximum (60cm) work area to match my workbench and not have anything protruding out the back. But I may have to review that.

With your bench design, you may have the opportunity to put a false floor/base above your bench and put a fan underneath, effectively pulling the air downwards. I noticed that a lot of the high end booths do that and a lot of people in various threads I read swear it's the best way to do it.

Also, one other other idea I came across when researching that might suit yours is someone used an old oven/hob extractor hood to great effect. You get the filter already there, a few hundred watt fan, speed control etc all built-in and all you would need to do is add the 100mm ducting. Probably plenty of old extractors like that on eBay.

 

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Some very neat ideas there @casethejoint.  I have a couple of snail-type extractor units, one of them is pretty big, if I can find what I did with it.  I ran it in my old place without a filter and the turbine is coated with a lovely lumpy paint effect in various colours :D 

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Booth got some action again today. Rear tailgate and sunroof for an X150 SRB.

I have now tested a few filter materials - 2mm black carbon stuff on eBay, some white paper-like stuff very similar to disposable face mask material and the classic dish cloth.

Surprised myself but have to say that classic dish cloth wins, by a fair margin. Excellent balance between "catch the paint" and "don't constrict airflow too much". On top of that of course it's cheap and very easily and readily available.

With my airbrush (typical acrylics at ~14 psi) it keeps up pretty well and almost no overspray/fumes leave the booth.

With rattle cans (I use Halfords here in the UK but I imagine worldwide they're probably not that different in terms of pressure etc) it does struggle to keep up and if you don't pause every few seconds you can see a build up of fumes and overspray inside the booth that gradually creeps out. Reality is I'll continue to spray rattle cans outdoors when the weather is good, but I can airbrush year 'round in the garage now :)

If you look at this pic you can see what the dishcloth is catching (it was originally blue + white). I can't find any overspray anywhere in the garage (and it would go *everywhere* before I built the booth :) ).

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