John Thomas Interview. Xrays and guitars.

John Thomas Interview | 2010 | Features

Best known as the X-ray guy, Law Professor John Thomas has been a prolific freelance writer with an excellent eye for detail and turn of phrase. His latest works on Kim Walker and the Larson Brothers has brought him greater recognition from players and luthiers alike.

We’re very fortunate to pry John away from his work to speak to us about his projects and inspirations!

TT: Hi John, thanks for taking the time for this interview. I have known you from the various articles you have written for various magazines- how did you get involved in that?

JT: My primary motivation to begin writing for magazines was … boredom! Really. I practiced law for about half a dozen years and then became a law professor about 20 years ago. Since beginning my teaching career, I’ve written dozens of articles for legal and medical journals. I love the creative aspect of writing, but yearned to write about a subject I’m even more passionate about and in a context that allows for a more creative presentation. Music magazines, and guitar magazines in particular, presented the ideal for me: I write about guitars, guitar makers, and guitar music and I don’t have to footnote my references!

TT: I also noticed most of your articles had a vintage Gibson bent to them…

JT: Well, I think that I’m a contrarian at heart (just ask my wife and kids!). So, I’ve gravitated away from the vintage Martins that the other vintage guitar obsessed folks tend to gravitate toward. In addition, I really like the “different.” Plus, my playing tends toward blues and ragtime. So, both my guitar choices and my writing have veered toward vintage Gibsons and Larsons. Both makers offer a sort of “bite” that appeals to my ear and suits my musical preferences.

TT: Ah, so what are you playing at the moment?

JT: I’ve got a gaggle of old Gibsons, including a 1931 Argentine grey L-2, a 1929 Nick Lucas, and 3 Banners: 1942 LG-1, 1943 SJ, 1943 L-50. My slide guitar is a 1931 National Style 1 tricone. Then, I’ve got a few Larsons, including a Dyer harp guitar. My modern guitars are 3 Kim Walkers, 2 of the Nick Lucas size and one that’s the size of a J-18

TT: And your current favorite?

JT: I’m particularly fond of my Kim Walker guitars. I’m fortunate to have three of them. Two are of the Gibson L-00/Nick Lucas style and one is his SJ style, based on the Gibson J-185 body shape. Though I rotate through all of my guitars, I’ve been playing the Walker SJ a lot lately. It’s maple/Adirondack with Kim’s hand rubbed, “Loarburst” finish. It’s also got a custom inlay. I drew a crude “S” shape for Kim and asked that he come up with something of about that size and shape, but more artfully done, of course. He got out the jeweler’s saw and bits of different colored abalone and produced what you see in these pics. It’s a wonderful instrument in every way.

TT: You mentioned you prefer the Gibsons and Larsons as you play blues and ragtime- maybe I could give you the difficult job of letting our readers get a feel for why this is so?

JT: Well, as we all know, great players can play any style of music on any kind of guitar. Alas, I’m not a great player. In addition, probably through recordings and listening to great players like Paul Geremia, I’ve come to like a a slightly rawer tone with blues and ragtime than with, say, contemporary fingerstyle. To my ears, maple and mahogany Gibsons have an emphasized midrange that suits blues and ragtime. They also tend to have a shorter sustain that comparable Martins. Brazilian rosewood Larsons have an exaggerated top and back radius and laminated X-braces that make them fall sort of in between Gibsons and Larsons: they’ve got that Gibson bite, but some of the Martin warmth. Plus, the design gives them really great clarity and sustain. So, again to my ears, they are the ultimate ragtime machines.

TT: Great stuff- but your analysis isn’t really limited to what you can hear – most folks will know you as that x-ray guy….

JT: Well, I suppose that it’s good to be known for something! I’ve been doing the X-rays (and CT-scans) for several years. It started as an adjunct to the Banner Gibsons book I’m writing with Willi Henkes. I wanted to document the differences between wartime Gibsons and those produced before and after the war. The images were so interesting that I expanded the project and I’ve now X-rayed and CT-scanned somewhere between 60 and 70 historically significant Martins, Gibsons, and Larsons. The imaging staff at my university and I have even written 2 articles about the project for the journal of the American Society of Radiologic Technologists.

TT: And are there any great revelations?

JT: I’ve learned a lot from doing the X-rays! In our first article, we documented differences between the Banner flattops and Gibson flattops built just before and just after the war. Simply put, the Banner guitars are just a bit more refined. Our technology allows us to measure to the 1/10,000 of an inch. The bracing and plates on the Banners are just a bit thinner, a bit more delicate. In our second article, we documented the evolution of bracing positioning.

I think of my data base of images as a treasure trove of guitar research. I’ve got Martins from what’s possibly the very earliest guitar to be branded a “Martin” though the late 1940s. For Gibsons, I’ve got images of some of Orville’s hand-carved, pre-Gibson company instruments through to a mid-1950s SJ-200. And, I’ve got an array of Larsons, including small, large, and harp guitars. The next big imaging push will occur next fall when I host the 9th annual Harp Guitar Gathering. I’m anticipating X-raying and CT-scanning a variety of Knutsen, Larson, and Gibson harp guitars.

A 1932 Gibson L-00 awaiting its X-rays

TT: Were there any difficulties in getting the guitars xray’d?

JT: There were no difficulties whatsoever in getting the X-rays! I teach a a university that has a great health sciences program (and a medical school on the way). With great trepidation, I’d emailed the imaging staff with my proposal to X-ray guitars. I anticipated that I’d be told, “we have far more important things to do.” But, the faculty answered that they thought the idea novel and very cool and jumped at the chance to work with me. It’s been great fun working with these folks.

TT: And how about the technical aspects? Maybe you could talk us through an example of how you would interpret a guitar xray- the various densities…

JT: With X-rays, we take full series of 4, overlapping images, first from the top and than from the side. It’s a digital machine, so I can then stitch the individual images into a complete, seamless X-ray from the top and from the side. The obvious thing the we see is precise brace placement of the bracing. So, I’ve been able to document Gibson’s transition in the mid to late 1920′s from H to A to X bracing. Similarly, I’ve documented Martin’s move from forward to rear shifted X bracing. And, because the the machine provides for precise measurement of everything, I’ve documented Martin’s transition from 1/4 in. thick bracing to 3/8 in. thick. The side view x-rays have, for example, let me determine when Gibson ceased using a bandsaw to cut dovetails to using a router. It’s like industrial archaeology.

The CT scans are a whole ‘nother matter. We’ve got an absolute state-of-the-art machine. a typical CT scanner takes an X-ray slice every 5 mm. Ours takes a slice every 1/3 mm. The guitar goes through the machine twice, first slicing vertically and then horizontally. The attached computer then assembles huge amounts of data into 3 dimensional images that you can rotate before your very eyes, Best is that you can peel away layers, leaving just the exterior in see through view or just the bracing. You can even look from the inside to the outside, again at just the bracing or whatever.

Our latest experiment was to run chunks of tonewoods — Brazilian rosewood, EIR, Honduran mahogany, Red spruce, Sitka, etc, — through the CT scanner. We got density readings on the samples and we can now run instruments through the machine and produce definitive determinations of the species of woods used for their various components.

John says: "A 1943 Gibson Southerner Jumbo. You can see that the X-ray really does let you look through the instrument. The position of all the bracing, X, tone bars, and finger braces, is easily noted. The machine also lets us measure the thickness of those braces to the 1/10,000 of an inch. You can also see that the neck does not have the customary metal reinforcing rod."

TT: I bet the costs are pretty high!

JT: The costs are nonexistent! My university and colleagues love what I’m am doing and have supported me completely. I’ve shown my gratitude by writing articles for scholarly journals and, rightfully, given first authorship to those who know everything and do all of the work. Plus, I bring really good sushi for lunch!

TT: And how about your plans for the future?

JT: I’ve got so much going on in the present that it’s hard to think about the future! Regarding the imaging project, some of that will find its way into the Banner book, some into articles, and I’ve plans for a book about the evolution of the American steel string guitar.

I’m also involved in two projects that I’m really excited about. The first is the Buddy Holly Guitar Foundation that I founded with Buddy Holly fan Peter Bradley of the UK and luthier Rick Turner in California. We’re building 18 replicas of Buddy’s 1942 Gibson J-45, each with an original fret from Buddy’s guitar. We’ll loan them out to artists on 2 year renewable terms to raise money for school music programs around the world. On our board of directors are Maria Elena Holly, Buddy’s widow, Graham Nash, Jackson Browne, and Julian Lloyd Webber, Andrew’s cello-playing younger brother. Our artists include Graham, Jackson, Brian May, Peter Frampton, Dave Stewart, and other great guitarists. You can learn more about the project on our website:

The second project is the film Alive and Well: Based on Bradley Denton’s great, comedic sci-fi novel, Buddy Holly is Alive and Well on Ganymede, the film stars Jon Heder and and filming will begin next summer. I’ve just agreed to put the music together for the film. This one promises to be great fun.

©Terence Tan.
Pictures courtesy of John Thomas & Kim Walker

Any infringement of copyright or errors is entirely unintentional- although we try very hard not to make them. Any guitars represented remain property of their current owners. Any issues should be address to: We will attempt to resolve these issues quickly.

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One comment

  1. Yiannis says:

    John Thomas is a talented person and a guitar afficionado too.
    I’m lucky having him as a friend.
    Thanks for the interview!


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