A few simple tricks to help keep your bridge healthy and warp-free
By James N. McKean
A version of this article first appeared in the July 2015 issue of Strings.
When you pick up a manuscript, the notes are all there. It takes an amazing level of training and technical skill to play it at all, but it’s your own artistry that transforms a sheet of paper to musical notes that sing. Cutting a bridge for your instrument is much the same. On a technical level, it requires the highest level of skill and precision. But working with the knife to give the instrument its full voice is where the art comes in.
While there is not much more fun than making a bridge, there’s nothing more frustrating than having to replace one. If properly cared for, they can last a lifetime—or several lifetimes, in fact. I see bridges cut 50 years ago at the long-shuttered Wurlitzer, or even older, from the Hill shop. It takes half a day to make a cello bridge, which means that for you it’s a very expensive proposition—a cello bridge at a top repair shop can easily cost $700. The raw blank itself is $60.
Luckily, for you, taking care of your instrument’s bridge could not be easier. In fact, there’s only one basic requirement: Don’t let it warp. And that’s easier than you think—just a couple of precautionary measures on your part will greatly reduce the chances of it ever happening.
The bridge represents a delicate balance of flexibility and strength. It has to be able to withstand the immense pressure of the strings (up to 85 pounds on a cello) and still transmit the vibrations to the body. The bridge is also shaped to move—the crown rocks back and forth. In order to do this, it’s very carefully designed. If you look at your bridge from the side, you can see the belly on the front as it tapers from the width of the feet to the narrow top where the strings rest. But while the back appears flat, it’s not—there’s a slight roundness planed into it so that it doesn’t collapse.
But, it only works if the bridge is standing perfectly upright. The wood for a bridge is selected from the hardest, most narrow-grained maple that can be found. Even so, it’s still wood—and if it pulls forward, it will very quickly start to bend and deform. The key to preventing warpage lies in the strings. At full tension, they hold the top potion of the bridge in place. But as the strings are tuned, they can pull the bridge’s top forward. This is not usually a problem because when you’re tuning one string, the other three hold the top in place.
It’s when you are changing strings that you have to be most careful. When you take off the old string and put the new one on and start bringing it up to pitch, it rides over the groove. Even though the strings seem to be perfectly smooth under your fingers, they are not. Most strings have a winding on them and the winding can pull the bridge forward. There’s a simple trick you might have seen your repairman use that greatly reduces the effect: Before putting on the new string, take a soft pencil and rub some graphite over the notch where the string goes. At the same time, put some in the groove on the top nut.
As you’re bringing the string up to tension, lift it clear of the bridge until you can’t hold it free any longer, and then do the final tuning. This helps to equalize the string’s pulling forces in front and behind the bridge.
Now comes the important part: Only replace one string every two days. Never put on a full set at the same time. All new strings—even metal ones—will stretch as they settle in. If only one string is stretching at a time, the tension of the other three will hold the crown in place as you gradually adjust the pitch of the new one. But if you have all new strings, the crown will be pulled forward as you do this final tuning.
Remember to keep an eye on the bridge when the strings are all at full pitch. Next time you are at the shop, ask your repairer to show you what the bridge should look like when it’s straight. All bridges deform to some extent and what you need to know is the proper setting for your bridge. If it has pulled forward, I strongly suggest that you take it to the shop to have it set right. The crown is flexible, but it can be hard to get it to move. If it binds, and you pull too hard, the bridge might come all the way over. And that would be a disaster. I’ve seen a cello top smashed by the impact of the tailpiece’s fine tuners crashing down on it. Also, the top is very flexible. In concentrating all your attention on the bridge, you might inadvertently lean your elbows on the top and crack it.
This past winter, at least in my part of the world, saw wild extremes in the weather—on one or two occasions, the temperature dove fifty degrees in twelve hours. That causes abrupt changes in the tension of the strings, which can make the pegs pop free and the strings go slack as the wood expands and contracts with the temperature and humidity changes. In this case, the safest course of action is to take it to the shop to have it properly retuned. If the bridge fell down, there’s a good chance that the soundpost is also out of place, plus bringing the strings back up to pitch will likely pull the top of the bridge forward—which will result in a warped bridge.
When the bridge does warp, it can be straightened. But like a sprained ankle, it will never be as strong as it was. The best course of action, for everyone concerned—you, your repairman, and your cello—is to stagger changing the strings, use a soft pencil on the bridge and nut slots when you do, and remember to check the bridge every now and then to make sure it’s still straight.
Want more instrument and bow care? Try Strings’ Violin Owner’s Manual. We also offer a handy series of web guides: Care & Repair of Violins or Violas, Caring for Your Violin or Viola Bow, Care & Repair of Cellos, and Caring for Your Cello Bow.