Time for a bit of lutherie techno-babble

I've been working on three instruments. I started them more than two years ago, but building time is hard to come by on an average day. When I really need to make progress, I wind up doing most of my work between midnight and 2 a.m. I've been putting in a lot of those late nights recently because aside from needing to get these instruments into the (very patient) players' hands, there is a convention with a competition coming up in November that I would like to have an instrument for. If I can reach a point where I can start varnishing before the middle of October, I think I'll make it.

I share what I do online, both on Facebook and Instagram. I like answering questions for people who know little if anything about the process, and comparing notes and techniques with fellow luthiers who may do some steps differently. I make a point to stop and take a picture when I'm at a stage that would be visually interesting, but I don't share everything.

Among the things I don't tend to share are certain setbacks or mistakes. Not really because I'm embarrassed—mistakes happen and are often a good learning/teaching opportunity—but because the kinds of things that come up would take too long to explain, and I don't have a lot of time to spare. There are also sometimes things I have to ponder and make decisions about that are equally hard to explain succinctly. So I thought I might take a moment to lay out an example of that kind of problem here.

The most recent step I've been working on is graduating my back plates. I get the arching—the curvature of the outside of the plate—finished first, and then the scooping out of the inside of the plate is done with a combination of goals in mind.

As with most steps in violin making, I start with the largest possible tool, and work my way down to tools that remove smaller amounts of wood as the process becomes more refined. In the case of graduating, I start with large arching gouges, then move down to finger planes, and finally to scrapers.

 

 

I wrap my fingertips but I still got a small blister this round

 

So the factors involved that inform what wood I move from where and how much are: Thickness forming certain symmetrical patterns, tap tones related to the final pitches created on the top plate, flexibility, and weight. 

I have some basic patterns I learned in school that I form by measuring in from the edges of the plate to areas known as the break points and stop, as well as a "thin spot" that parallels the outline, the center, and some transition places. I check the thickness of the plate at these points with a set of calipers, and keep adjusting until I have the symmetry I want and the measurements I'm looking for. The school patterns are a starting point. I have a few ways of flexing the plate in my hands to see if it feels right, and if it's too stiff, I keep removing wood until I like it better.

I also start checking tap tones. There are two I'm interested in: One where you hold the plate at the thin spot along the upper bass bout and tap where the soundpost will eventually go, and one where you hold it in that soundpost area and tap a lower edge. I hum the pitches I hear into a tuner (currently using a link on my laptop) and note the pitches. Ideally, I want that first tap tone to be within a whole step of the octave tap tones I got when graduating my top plate, and the second tap tone to be a third, fourth, or fifth away from the first. My teacher's mantra about this, however, was "Don't hang on tap tones." They are the least important of the factors I'm trying to achieve, but still of interest, and if I can manipulate them to where I want, I do.

The final thing is weight (measured in grams) which I'm rather new to. We didn't discuss weight as a factor in school, but I suspect it generally falls in line when you accomplish the first three things. I discovered in discussions with luthiers over the past few years how many prioritize weight in the graduating process. The weight to aim for varies based on density and quality of the wood, but there is still a range that is useful to know.

Viola plate telling me how much more wood to remove

Now with all of those factors laid out, here's how my graduating went this round. 

The Amati model violin that I'm making for my daughter ended up 4g heavier than I wanted, but I like the flexibility. The tap tones were confusing. The top plate was a clear F, but the soundpost tap on the back alternated in my ear between sounding like an F# (yay!) or a C# (boo!). I know there are overtones, and both pitches are probably present, but I feel better when I get one clear pitch. I really didn't want to go thinner anywhere. I was pushing it with my measurements because I wanted to bring it into the better weight range, but I decided since the flexibility was there, I'm not going to worry about the last bit of weight. I can't drop below certain numbers without compromising structural integrity. Here's a picture of the plate held up in front of my bench light so you can appreciate how thin it is.

The viola I managed to get down to a weight I'm happy with, and good flexibility. The tap tones I think are okay, but the top was the one this time where the pitches were confusing, so it was hard to know what to match to. The graduation was definitely on the thin side, but that's where it apparently needed to be in order to flex properly.

The Guarneri model violin as of this writing I am still pondering a bit. I'm scared to take it any thinner, but I still don't like the way it's flexing, and the weight is almost 10g too heavy. The tap tones are great, but I'll probably have to sacrifice those to trying to make the plate less stiff. But I have no idea where to take the weight from right now. I may switch to tuning my bass bars for a while and come back to it.

Part of what makes violin making interesting is that it's never the exact same process twice, and there are always ways to improve your skills. Occasionally a step will go perfectly, and there is certainly satisfaction in that. But most of the time there is problem solving to do, and new circumstances to try and hone your abilities. 

I think often about my mom describing how as an artist, when she used to work almost exclusively in watercolors, that the day a painting came out exactly as she had imagined it and there were no surprises, it inspired her to move on to a new medium. Craft is about replicating things cleanly. Art is about exploring something new. The beauty in violin making is working in that crossroads, where you are creating a tool that needs to work properly, and also making it uniquely your own.

Each new instrument gives me the chance to try and improve upon what I've done before. I can't wait to hear how these latest instruments sound. And I already have ideas for the next batch.