The Springboard (Pt. 8, Polyurethane)

This is the eighth of a number of posts pertaining to the progress of my 21M.299 (The Social Lives of Instruments) final project, The Springboard.

The final third coat of poly, freshly applied.

I finished my last post by contemplating whether I’d need to add another coat of stain, or go straight to the polyurethane. Since I was happy with the color, I went straight to the polyurethane.

I’m using one of the unused suite lounges in my dorm as a work space. This was great for applying stain in the morning, but I was going to apply the polyurethane in the evening and unfortunately the room’s lights were out. Fortunately, generations of prior students had left their lamps in the room.

Behold! The circle of lamps!

With lamps on and old newspaper strewn about, I began my work.

For this project I’m using clear semi-gloss polyurethane. I would typically have gone straight for the satin finish since I think satin looks more modern than high gloss, but figured a bit of gloss may help it look classy. The directions warn to stir, not shake. Apparently it wasn’t a fan of 007. I planned on doing two coats as per instructions, but ended up doing a third on the front and sides of the instrument’s body.

With the poly ready and my cheap bristled brush in hand, I started with the smallest pieces. The instructions say to use a thin coat, so I did as such. The pieces were done in no time, so I moved on to the back of the instrument’s body. Making sure to not create any puddles or drips, I was surprised by how much surface area could be covered with very little polyurethane. Soon I was done with the back.

Proof that I was actually doing this. Photo Credit Yara.

Happy with how the back of the instrument was drying a few hours later, I flipped the body over and repeated the process it on the front and sides. I had to lightly dab some drips that formed on the bottom of the body, but since it’s the back I didn’t mind too much.

The components with their first coat of polyurethane.

The following morning I prepared for applying the second coat by lightly sanding all the components with 220 grit sandpaper. This roughens up the finish so that the next coat can adhere better, and also smooths out any small imperfections that may have occurred. After wiping the dust off the pieces, the second coat went on mostly without issue. Two minor issues compelled me to do a third coat; first some wood dust landed on the front of the piece shortly after I applied the coat, and I also found a drip that left a very obvious mark on the front. I hoped the sanding before the third coat would remove these imperfections.

The same evening (today) after classes I repeated the process to apply a third coat to the front. The dust disappeared and it is drying as I type this. The gloss is increasing with each coat, but is still where I’m happy with. In retrospect, I’m glad I added the third coat as it should hopefully better protect the fingerboard from scratches. Now to let it dry for 24 hours…

Remaining Tasks

If I really wanted, I could make the instrument look even better by sanding it with even finer grit sandpapers, putting on a thin layer of polish, and then waxing it. Given my temporal and financial constraints and the fact that this wasn’t even a nice wood to begin with, I’m not going to bother.

After the pieces have finished drying, I will rebuild the instrument and make sure everything still fits together and it works as expected. The final task will be figuring our how to mount the piezo transducer. I will experiment with that then, but am likely going to epoxy the center of the transducer directly to the rear of the instrument near the spring mounting screws. Until then!

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