Questions: Ebony Tailpiece Cracks

by Ted Megas

Originally published in American Lutherie #73, 2003 and Big Red Book of American Lutherie Volume Seven, 2015

 

Susan from cyberspace asks:

I have a new custom-made archtop and the ebony tailpiece has developed a few very thin/small cracks. Should I use lemon oil on it? I have a humidifier in the room, but it seems impossible to keep the humidity at a constant level.

Ted Megas of Portland, Oregon responds:

I would be concerned that the structure of the tailpiece is undermined. A cracked tailpiece is potentially a very dangerous situation, since it’s under a lot of tension. I’ve even heard of tailpieces exploding. Lemon oil will neither fix the cracks nor prevent further cracking. You need to be in touch with the maker of the guitar or a reputable repairperson.

The cause of the cracking would be my concern as a builder. It’s absolutely imperative that the wood used for tailpieces, fingerboards, and other fittings be quartered and aged properly. Buying blanks from wood suppliers is not a guarantee of either. In fact it’s almost a guarantee of the opposite — wood sawn every which way is now sold for these purposes. Most suppliers gave up on trying to cut quartersawn fittings and fingerboards years ago. And a lot of makers, including factories, are ignoring the grain-orientation when selecting parts. Only cutting it for yourself or personally selecting precut pieces with sufficient knowledge to know quartersawn wood when you see it, aging it properly, and using in under the proper humidity conditions in the shop will insure stable wood.

I caution people who own my guitars to keep humidity at about 45% relative, give or take 20%, especially if they requested slab-sawn backs such as quilted maple. This is not difficult to achieve in most situations with a small room humidifier or with a dampit, especially when the guitar is outside its home environment. It is really the builder’s responsibility to build under proper humidity conditions, which makes humidity variations a lot less critical for the owner of the instrument. Most hygrometers, even expensive ones, are useless unless calibrated regularly with a sling psychrometer, which you can buy for about $80. It’s really the only way to know what your building conditions are so you can maintain your shop humidity within acceptable range, which for me is 40%–45%.