Introduction

Are you shooting nitrocellulose (or something else) on your instruments, then you need a spray booth! Spray booths serve multiple functions in the spraying process and are vital to getting a clean finish. A booth not only keeps bugs and dust from settling in your fresh finish, it also keeps spray particles from adhering to everything in your shop while also creating a more controlled environment inside a workshop that might be too humid to spray in (in winter for instance).

You’ll see a variety of spray booths on YouTube or Instagram that range from dedicated rooms with heavy filtration to smaller stations that capture over-spray. These are great if you have the money and space to do this, but not mandatory to get a great finish on your instrument. I’m going to show you how to make a spray booth on the cheap that will suffice until you’ve decided to create something more substantial.

(A note…I previously had a dedicated spray room in my old shop. BUT I decided to step away from making fretted instruments and focus on violins. Shortly after, I moved my shop to a smaller (but better) space without a spray room. Low and behold a year later I needed to spray something, so I made a booth!)

Outline

Planning your Booth
Materials Needed and Costs
Frame Assembly and Draping
Other Considerations That Could Make Your Finish Better

Planning Your Booth

First thing is first…where are you going to put your booth?? How much space do you need to create a booth that’s big enough for your needs? How much light is there in the room? Is there power nearby for your air compressor and extra lights? (I’ll talk about these later) What kind of ventilation does the space have? Is it a dusty space or relatively clean?

Next thing to consider (which is important), is how large you need the booth to be. Are your instruments small like a ukulele or large like a guitar? I personally like to hand hold my instruments and turn them while I’m spraying them to help them stay even, so I like a little extra space. Also, what are you going to hang your instrument from while it dries? You’re going to need a place to hang from in your booth, and I’ve laid out how to do that.

Materials

The materials part is really simple! You don’t need anything fancy here, just some pvc pipe and plastic painters plastic sheeting and a bit of tape!

PVC Pipe: For the pipe I recommend going with the ¾” pipe in “schedule 40” due to its thicker wall, hence giving a bit more stability in the structure. All of the fittings will of course be ¾” as well. I made a 7’x7’ booth so I got the 10’ lengths of pipe. (12-pieces = $60.36)
Fittings: 8 Side-Out Elbows, 4 Tee’s, 1 Cross, 4 Couplings ($45.93)
Painters plastic: a 5-pack of .7mil 9’x12’ plastic drop clothes. ($9.98)

Out the door the cost was around $120 from Lowe’s, which isn’t terrible considering a little work you’ll have a collapsible spray booth!

Building Your Booth

Since you’ve already decided how big you want this booth to be, it’s time to cut your pieces. As a luthier I’m sure you have a variety of saws at your disposal, so use whatever floats your boat to cut your pieces (I went with a sawzall). I went for 7’ lengths for the base and vertical risers, keeping the 3’ off-cuts for later.

The top two 7 footers for the front and back side of the booth were cut in half (3’6”) to make space for the tee’s that will allow for the cross-bracing up top. I wanted the center of the cross to be more towards the back of center, so the upper side pieces were cut at 4’ and I used some of the 3’ off-cuts from earlier to complete the length of the piece. Once the upper cross is assembled, it’s time to drape some plastic cloth.

For draping there isn’t a whole lot of rhyme or reason to it. Just make sure you get some on the floor and cover your gaps as best you can because that nitro will go everywhere. Be sure to cover the top and to leave yourself an opening! I went with a tent-style opening that I could close behind me. Apply your favorite painters/masking tape liberally and try not to rip the thin plastic as you put it up. This plastic isn’t meant to hold up over a long period of time, and will likely have to be disposed of when you disassemble the booth. Heavier plastics are available if you want it to be more substantial.

Easy peasy, lemon squeezy!

Other Things to Consider

Here are a couple other things to think about that will make your job easier.

Ventilation

You’re going to need this! Dedicated spray rooms have fume collection hoods (or even walls) with big heavy, grounded fans. This is great if you have a few thousand dollars sitting around but isn’t realistic for someone starting out or doing one or two instruments a year. One way of doing it is to have an opening in your booth big enough for a box fan. On that box fan attach a HVAC filter of your choosing so it collects particulate before it goes through the fan (get a few because you’ll need to change them as they collect particulate and clog). Note this will pull in air from outside your booth. (Dedicated spaces have filtered air intakes) ALWAYS WEAR A RESPIRATOR!!! Nitrocellulose isn’t something you want to breathe. Respirator, glasses, head covering, long sleeves, etc are recommended. (Check the state/county/ordinances in your area regarding spraying finish as it might impact how you do things)

Lights

You may have good lighting in your place, but you can always have more! I highly recommend mounting a couple cheap aluminum light fixtures to the inside of the booth. With them get some full-spectrum LED floods. They make a WORLD of difference when it comes to really seeing how your finish is landing and making sure your coverage isn’t too much or too little.

Humidity Control

I cannot stress how IMPORTANT this is. If you’ve sprayed in a damp place (or when it’s raining outside) and gotten the iridescent white layer in your finish then you know how frustrating that can be and how much time you’ll spend to fix it. Hang a little humidity gauge in your booth to help you keep an eye on things. I’ve gotten away with spraying at 50% humidity in the past, but that’s playing with fire in my experience. Best to have ambient humidity below 40%. If your shop get pretty damp, a good thing to have around is a dehumidifier. I have a Hinsense model digital dehumidifier and it works great.

**Note to remove the dehumidifier from the booth before spraying, you don’t want nitro getting in the machine and nor do you want the machine to spark the nitro particulate and turn your booth into a fireball.

Spray Gun

HVLP (high volume low pressure) spray guns are the only way to go when it comes to spraying nitrocellulose. I purchased my DeVilbiss Finishline FLG4 (gravity feed) from an autobody supply shop a while back and it’s been a workhorse for me. They are pricy but they clean-up well and spray consistently.

Air Compressor

There are so many air compressors out there that will do the job, so this is just my setup. I use the Kobalt Quiet Tech 26gal compressor. No frills, but it gives me more than enough air to spray guitars without having to worry about my pressure changing as I get near the end of each round, plus it’s easy to roll out of the closet when I need it.

On the compressor I’ve installed and in-line moisture trap to catch any water that might sneak its way into the line. Compressors condensate air as part of their process, and this isn’t a problem in most applications of compressed air, but it is here. You don’t want to put in the effort to lower the moisture content of your booth to then have some water in your air line muck up the works, right?! I run an IMI Norgen Water Separator to solve that problem. Install it with a couple pieces of ½” copper pipe, some sealing tape and a couple connector fittings and you’ll be good to go!

And that’s about it!

And that’s about it! This is just one man's way of doing this, so do what works for you. Follow your own path for spraying nitro and find what works for you and your woods. Keep notes on what you do! I can’t tell you how many times this has saved me. Be consistent with your work, keep your lungs safe (wear a respirator!), keep your shop safe and make gorgeous instruments for folks to enjoy for generations to come!

Cheers!
Ryan Davidson
Davidson Strings
www.davidsonstrings.com

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