Detecting top cracks in musical instruments
Pat DiBurro ◊ Master Luthier
The fingerboard on Hugh’s mandolin was troubled. Obstinate, stubborn, worn to the rails. A decade ago he cased the 2003 Collings MT2 with finality. Until deciding to give me a crack.
Leveling / crowning / polishing of the frets returned a degree of playability. But the same issue of fret wear eventually brought the day all musicians dread. Back to the shelf, the World Of Unloved Instruments.
Restoration of a professional-grade instrument is a specialty skill. Just removing old frets is a labor of patience and intuition. Several local shops practice the mechanics of refretting, but Hugh wanted the best. Full Throttle Top Hat. An artisan who works with passion, love, and purpose.
After exhaustive networking we locate the luthier ten hours north in Exeter, New Hampshire. What we wanted was the only way Pat DiBurro would do the work: OEM 18% nickel-silver fretwire sized .080″ x .040″ individually radiused to the existing wood, set as-new upon the bound ebony fingerboard. What we got back was stunning.
A new nut impeccably cut, string gap perfect, pair spacing precise. Fingerboard leveled, frets immaculately set. The fret ends were especially impressive. Two cracks nearly invisibly repaired with true New England ingenuity, its Collings tone noticeably improved.
ATB – How did you get such a perfect fret end dressing? The binding has not a stray file mark upon it. Was everything taped off except the fret?
DiBurro – The short answer is 30 years of doing that: the fretting tools, particularly the file; my fret file which I customized 30 years ago; it almost burnishes the fret end. It is all handwork; I did not tape the binding. The right angle will cut the frets but not so much the file will roll over and bite into the binding.
• The feel is perfectly consistant. Did you level and crown the frets?
For the most part, no, I do not fret level, but keep the original crown intact. You start with a level fingerboard.
• Did you cut the new nut by eye? The strings are spaced exactly like the old one.
DiBurro – No jig, just my Starrett 6” ruler using 32th fractions. I precut – scratch – four slots with an X-Acto blade, rub my thumb [dirt] into the marks so can see the lines. Using an OptiVisor, overhead looking straight down, a magnified bird’s-eye view, I can see if anything is drifting. If a slot starts to drift it will be filed back in line. Then nut files. The nut is much wider than the neck so I have room to move it either way.
Funny thing about the fretted instrument trade. Nuts and saddles are considered to be something any repair technician can do. Nuts are really challenging.
• Our thoughts too. The gap between the individual pairs is perfect even as string gauge changes. How did you learn how to cut an instrument nut?
DiBurro – I started by going to different music stores, asking if they needed any repair work done. One day I got the response, “We need a nut on this 5 string electric bass”. I took it home, made a nut, and got lucky. I was quite green to repair work, but I got lucky.
ATB – People who consistently get lucky performing skilled handwork are hard to find. We’re happy you accepted our job. It was worth every dollar, and then some.
• Tell us more about the frets. Are they set by friction in the ebony fingerboard?
DiBurro – No, with Collings, their frets are glued in with clear cyanoacrylate. I use StewMac #10 [by Stewart-MacDonald]; it’s viscosity is water-thin out of the bottle and cures in seconds. The CA wicks into the slot and freezes the tang to the substrate. It’s not a lot, just enough to ensure a solid bond. The hardest part is removing existing adhesive [within the fret slot].
• The tone is definitely improved. By the bridge saddle work or the top crack repair? That huge crack on the bass side of the bridge saddle, fixing that would have made a difference.
• Your invisible top crack repair is amazing. I thought it was a stress crack in the finish. No, it was cracked. Flapping in the wind. How do you know? I puddle naphtha first. Across the crack. It’s my crystal ball, allows me to see cracks or an area where finish has delaminated.
When owners come in with their instrument, I can remove strings, light up the interior, and run naphtha right over the crack. Using mirrors, the owner can see the dark line. Naphtha will bleed through the crack. No matter how tight the crack, the naphtha will get pulled right in. It’s capillary action. It will bleed through to the underside. It does not raise grain or do anything to the wood. Within a minute or so it evaporates.
• How do you get the glue into the crack? I use marine-grade epoxy. The epoxy, I heat it to 150˚F and it becomes as thin as water. No matter how tight the crack, it wicks right in. I use West Systems clear marine epoxy. #105 is the resin, #206 is the hardener, 5 to 1 ratio.
It’s very important to have the ratio as accurate as possible. Ten years ago I bought a high quality microgram scale, and have since gone over to weighing the product. Ambient temperature is also very important; 55˚F is the minimum I’ll work.
• You spend a few weeks per year at each of the Big Three (Martin Taylor Collings) keeping current on their techniques? Do you perform repair work for them as well? Yes, but the trips are more about understanding changes in production from the last visit. It is important to know if they changed a process or if there was a production hiccup to watch out for.
• What is the single hardest repair to do on an instrument? Usually correcting badly executed previous repairs.
ATB – Here is Pat performing a top replacement on a Taylor. • You remove a top by essentially carving it off the guitar? And you try to leave the binding intact? Yes, the outer binding is left intact and the new top is inlaid. This negates having to touch the sides. • Wow, and then you make a new top fit whisker-tight!
ATB – Pat received this Collings MT from a customer who had tried to remove frets themselves … It is not as easy as it seems, but all ends well under the focus of Pat’s Higher Calling.
What a long trip this mandolin has had. Shipped 2003 from Bill Collings, Austin, Texas, to Medley Music, Bryn Mawr, PA. Employee Tom Wade sold it to Hugh Mason. Hugh took it on the road, literally – the Porkchop Circuit. Then to Exeter NH and now back in the Commonwealth. Just in time for post-Covid bluegrass circle festivities … ∆