Explosion Proof Fans and home spray booth set up

Beau,
I had a production woodworking shop and was spraying 25-50 products a day, so I needed a dedicated booth and fan. I think that may be overkill in your application. We were spraying lacquer in our large booth and the OSHA guy told me about a table top unit that would suffice for when I was doing small projects. I'd look at table top or hobby spray booths. I'm guessing you're talking about spraying 1-2 instruments a week? You can get a complete booth for as much as you may have in the fan alone. Check ebay for some used ones. Some of them are even ventless. Here is an example by spray tech. Everything is contained in one unit.

Hi Anderw- that unit looks pretty good-

I just bought a 16" explosion proof fan for $275 which I will build into basically what is shown in your pic- a cabinet with filters at the back and the fan behind them- all enclosed in plastic cube with door and window with filters.

That unit looks cool for spraying non critical finishes, or, very small items, or ukes if it were installed in a clean room.

For spraying grain filled, polished, high gloss finishes, clean air is practically a requirement, otherwise a lot of time will be spent dealing with individual dust particles that settle in the finish. With filtered, dust free air and clean clothing, and a little basic clean technique, a 'recipe' can be developed for the finish that is desired. Coats can be built up quickly, with the actual spray time of each coat barely taking any time at all. One little dust spec in a sprayed coat throws a wrench into the whole thing. The polished, deep high gloss finish acts like a magnifying lens for any contaminants that happen to embed in the finish during application. Picking them out with a razor knife leaves a dent, which messes up the accuracy of the desired dry-film end result by the time the little hole is filled/ or sanded out. Trying to sand out some dust particles when the finish is still soft cured often just pushes the dust deeper into the finish, again messing up your finish' recipe'. In addition, sanding of troublesome particles is not fun! Effectively removing a dust particle that has settled into wet finish, and potentially touching into the softened previous coat requires waiting until the finish has cured a bit, more than an hour unless the lacquer is very thin. It is so much better to be able to do any sanding as it is needed on the instrument as a whole, not fighting dust. To be able to spray a coat, come back an hour later, spray another, and so on, without having to wait for the finish to cure hard enough to sand out the offending mess.

At the upper end of instrument finishing, knowing exactly how thick the dried film is, will play in to getting a consistent sound. This requires consistency in finishing technique, not chasing the whims of what happens to land in the finish during each spray session.

Spraying furniture grade finishes in satin, or even gloss lacquer is quite a bit different than spraying a gem like high end finish. In furniture grade finishing, a spec of dust here or there hardly matters. Not so with polished gloss little gems.

Lacquer can be sprayed quite effectively with zero fans at all, just walk into an undisturbed room, spray quickly, and leave, being careful to not stir up the dust with any airflow from the spray gun, or your feet/ movement. No fancy anything, just a spray gun and some abrasives. A properly designed spray booth is a tool that saves a lot of time in the long run if one is doing lots of really fine finishing. It can take the element of contamination and minimize it substantially. Time is money, and fixing finishes sucks.

Say someone finishes 40 ukes per year. If in the finishing process, they have to add another hour in dealing with contamination for every instrument, sanding at unknown intervals to keep it clear and smooth, not even counting the extra time to wait for finishes with contaminants to cure until they can be safely sanded, that is a lot of valuable time in the course of a year. Enough to justify some effort in cleaning things up.

Stink is not the biggest enemy in finishing. Getting a good finish is what is most important. Just because one stays safe, or doesn't make a mess with lacquer dust, that does not help at all if the finish is not good.

By the way.. another benefit of spraying lacquer at or near a 100% thinning ratio is that any potential contaminants can be removed more easily, as they are not embedded in as thick of a coat as they would be, say, if the finish were being sprayed straight out of the can in fully wet coats.


In a good spray booth setup, or a good location, contamination should not be much of an issue. Really, you do not even need a spray booth at all to achieve a very nice polished high gloss finish. A spray booth just makes it a lot easier to get there.

Chris,

You should get into the uke spraying business. I bet would do well!

Daniel

I have sprayed my lifetime recommended allowance of lacquer, but yes, you are probably correct. Guitar finishing also.


I am just beginning to explore binding, purfling, and inlay into my plinth work.

In the long term, there is a lathe and a mill in my future, for some specific audio related products.

Thank you Daniel.

Hey Beau, I didn't realize you meant a qualified cheap. I thought you meant cheap like me!

Good stuff Chris.
My spray room measures about 8' X 8'. The interior walls, ceiling and floor are all made out of heavy duty vinyl and made for easy removal and cleaning. I used to be in the art show business so I used my old art tent for this. (They are the ones you see at street art shows.) The better ones run around $2000 but you can often find used ones for a couple of hundred bucks or even free sometimes. Many even incorporate zippered doors in them. The cheap Big Box Store tents won't work. The walls I have are very thick, translucent, durable (I've had this one for 20 years) smooth and waterproof. The walls zip together with heavy duty zippers for easy removal. My floor is a single piece of linoleum that is laid on top of my existing floor. I periodically hose everything down and clean it well. I never spray toward the wall where the fans are. Instead I spray toward an adjacent wall on which I hang a 3' wide piece of kraft paper that runs from the ceiling to the floor. This is simply tacked on and replaced often as overspray builds up. I won't mention what kind of fans I use because I don't want to be responsible for anyone's misadventures. BTW, one of the reasons I like using an HVLP system is because the lager particle size produced keeps the air cleaner.

Chuck-
Your market vendor tent thingy is a really good idea for easy setup and breakdown. I only want to keep the booth up when spraying a batch and not all the time.

Previously, i was thinking of something similar to Japanese style walls with plastic instead of rice paper, but the market vendor tent (at least the frame) has benefits over this,

Beau, Black Bear is right on.
Ideally, the CFM of the fan needs to meet or exceed the internal volume of your closed spray booth.
A 6'x6'x8' booth would be 408 cu ft. so a 240 CFM bilge pump wouldn't be sufficient by most standards.
You also need to decide where the intake air coming into the paint booth is coming from....since you live in Colorado.
If it's coming from your shop, it will be sucking your heated shop air right outside. Might get a bit chilly in winter.
Most serious builders booths that I have seen are rigid construction with sealed sheet rock walls.
Often they will use a sliding glass door for the front.
Additionally, you might look into some kind of speed control for your fan. After you've sprayed for several hours and the instrument is in the flash-off stage, you may wish to reduce the airflow tip it has completely based off, which could easy exceed a day.
Good luck.

Mark

Partially correct. In a booth that is engineered to this standard, inlet air is filtered, and well... not just a passing thought of some filters that kind of work, kind of not... Strong airflow without filtration means that you will just be creating expensive sandpaper. Honestly, you do not really need ANY airflow. What you need is ZERO dust settling in the finish. With zero airflow, however, the lacquer mist will become similar to dust. ( though it is small, shrinks, melts in, and is clear) However, if the gun is set up right, and/ or you are using a turbine driven HVLP, the amount that settles in the finish in the first 3-5 minutes, which is when the finish is still the softest, the finish just cures the slightest bit hazy, and most often it can be sprayed right over in the next coat. Downdraft filtered airflow acts like a 'curtain' in protecting the freshly sprayed finish from having particles land in it. This is how top level spray booths are designed.

If you engineer a booth solely with the parameters of (given) volume, equals such and such airflow, without the inlet air being completely filtered, and also without thought to the direction, and other qualities of the the total airflow in the room, you will just be moving dust into your finish, guaranteed.

One nice spec of some airborne particle is going to slow you down, a lot. More airflow, if it is unfiltered, means more potential for dust.


The reasons for high airflow in a booth are to minimize overspray from landing in the finish (which is an insignificant problem in comparison to dust or other foreign contaminants) and also MOSTLY (where spray booth regulations come from) to protect the operator. In reality, it takes very little airflow to keep overspray from being a problem.

Double or Triple layer, glued 5/8" drywall construction, with a sliding glass door, and excellent filtration on the inlet side, and enough airflow so that the operator does not really even need to wear a respirator, YES! that's awesome! That is how a spray booth really should be built. If you cannot quite muster that, In my experience, clean air is WAY more important than quantity of airflow.



With the only design parameters being considered in designing a booth as being 'x' amount of airflow in ratio to a given booth volume, and not exacting consideration to filtration... well, good luck with that.


And, if you are sucking unfiltered air into a booth from a woodshop, that is a recipe for a lot of work and inferior finishes.



Those Can filters, like this: http://www.canfilters.com/canfilters_150.html connected to an 8" can fan with insulated flexible ducting, and then led into an industrial HEPA filter, or at least an 85% ASHRAE filter would make an excellent filtration system with minimal effort, and the carbon filter will work well when run as a circulating fan in the shop for particulate matter and also for residual solvents. I have had one of those (the 150) running 24/7 in my shop for 5 years now, It is awesome. It is almost silent. For the first year or 2 of the filters life, it will also work for solvents. I have owned one of those metal box woodworking filters with the squirrel cage and the cloth bag filters. Those are a total joke to a setup like I just described. Aside from clogging immediately, with severely reduced airflow, squirrel cages are noisy and energy inefficient.


I guess I should also state, that if you are doing lower or average grade lacquer finishes, like satin, or unfilled, unpolished finishes, you can get away with a less exacting environment. I am talking about how to cost effectively ( on the cheap) spray a tip-top quality, fully polished gloss finish. The kind that, honestly, I do not see too many builders doing, and many that do hire the finishing part out. Of course, just having the booth and a good gun/s does not account for spray skills, and experience based intuition.

I find it hard to believe that one couldn't produce high-quality high-gloss finish without double or triple glued dry-walled enclosure with a sliding glass door, et al., but perhaps I'm misunderstanding the suggestions. The suggestions given to me by the local pros included: filter your incoming air to keep dust out of the booth, filter your outgoing air to keep spray from building up on your vent fan, air intake source should be up high up in the booth, outgoing air should be lower and directly under whatever it is that you're spraying, or near enough as possible, because the overspray is heavier than air and will naturally want to fall, cfm should equal or exceed booth volume, otherwise you're not moving enough air to keep the fumes from building up and possibly escaping the booth altogether, seal the booth up best you can to keep the air coming into the booth restricted to the filtered intake vent, and clean your booth regularly to generally keep a clean environment. I think the idea of positive pressure is genius, as it pushes the air out rather than sucking it (and potentially dust) in.

Talking of explosion proof electrics ....I have a sparkless stop start switch , it consists of two mercury contact beakers.
Sealed in glass in a switch casing....the idea is that this switch connects to a relay breaker placed at a safe distance outside the danger zone, so no sparks occur when switching the fans or other equipment on and off.....It was designed for the petrochemical industry.....I've never found a use for it.

im going to use Japanese rice paper style walls, but with heavy plastic.

Each wall will have hinges and with cheap yoga matt rubber running up the wall edge that squishes together when at a right angle to form an air tight (enough) seam. (yes the yoga matt will corrode with acetone but not very fast with just fumes and over spray hitting it- i might seal it with shellac) I will do the same on the wall edge that sits on the floor, the weight of the booth will be enough to hold it down tight. along with a temporary plastic floor.

I've not thought much about a door and intake/outtake windows- something utterly totalitarian no doubt.

I build at home but spray at my work. I have my HVLP 3 gallon pot sitting on the floor next to the back door and I walk outside, spray the instrument then come back in and hang it up in the corner of my warehouse out of the way. So much for high tech.