A Stringed Instrument Relies on Its Ribs

By Christopher Jacoby

A violin consists of three basic parts: the neck and scroll, the plates—the top and the back, and the ribs. But at its core, an instrument relies upon its ribs, the bent sides of the instrument. They stand proud between the top and back with as little as 1 millimeter of thickness to support the torque of strings and bow.

While I have seen homemade fiddles with the ribs sawn out in a single piece from a hunk of hardwood, mainly and traditionally the ribs of an instrument are bent. Which involves heat. And if you’re planning to bend hardwood, you’re probably going to singe a few fingertips and break some maple before you get the hang of it.

There are a dozen ways to use heat to bend the ribs—NASA heat blankets over a form, a cauldron full of boiling water, a steam box and a spring-loaded mould, or whatever else your imagination can dream up. But the oldest way works about the same as the rest. You heat up a hunk of metal with rounded edges—be it an iron pipe, an aluminum or bronze form with the same curves as the C bouts of your instrument, or a copper saucepan—and you force the rib around it until it takes on the shape you desire.

“The iron must be so hot that water dropped onto it bounces off in popping droplets, instead of flashing to steam.”

Making a Form

So how do violin makers determine what shape they desire? We make a form. I use inside forms, meaning I bend my ribs around it against the shape of an outer form. Some others use outside forms and press their ribs into the form.

I start with a drawing, whether I am copying one of the great makers of the Cremonese Golden Period, or inventing my own outline. Forms are most often made from the outline of the back of an instrument, because the back is far less worn and distorted than the softwood top after years of playing and repair. If you are drawing a violin, you draw the corners, the C bouts between them, and the broad hips of the upper and lower bouts.


The shape the violin will have when finished is determined by the shape of the ribs. After many, many instruments, and some casual standing on the shoulders of giants, a maker can start geometrically and build an instrument from the form out. But to start, every maker is trying to emulate a great instrument he or she admires. With the top and back glued to the ribs, that great instrument must be built around the ribs as they were bent.

So to make a form, you draw backward, through the making process.

Take a look at your viola, cello, or violin. There is an even distance, on most, from the rib to the rounded edge of the spruce top and the maple back. Basses sometimes don’t have overhang—the distance from the rib to the edge of your top and back plates—but most bowed stringed instruments do. It’s nice to have an overhang on your plate edge, because Labrador retrievers, baby brothers, and patches of ice happen. An overhanging edge protects the most delicate part of the instrument—the ribs—from impact and disaster. The ribs are more or less an even distance in from the outline of the back, all the way around (though there are some variations in style).

To travel from a back outline to a finished form, you pass the purfling. The purfling is the black/white/black string around the top and back of your instrument. Very decorative—and just as utilitarian as the overhang of the edge in building an instrument to last.

In most cases, the purfling is not just drawn or scratched into the plate. It is three thin strips of wood: black/white/black, inlaid into a channel carved around the perimeter of your violin, scored with a wickedly sharp knife, and then hollowed out with tiny chisels. Makers bother to do this because when that Labrador or baby brother drops your violin onto its edge overhang and it cracks, the trench around the edge, and the three-strip purfling in that trench, stop the crack from running up the plate.

As a matter of philosophy, the form of the rib garland—the flexible body of the ribs and the blocks—sits right inside the line of the purfling, as it travels around the top or back. With few exceptions, this is true. Thus the rib garland is protected with two lines of defense, which is just good sense considering that disassembling an instrument to cleat cracks in the rib garland is invasive and expensive.


So if I am making a form from the back outline of a violin, I trace inside the inner black of its purfling, all the way around, and begin to plan for my blocks. The blocks are vertical towers of willow or spruce that stand between the top and back, and violin makers glue our bent ribs to them after carving them to the shapes of our form. The blocks are set into the form, and the fragile ribs are bent around them (and glued to them) to get to the desired outline.

Bending the Ribs

Then comes the actual bending process. For violin, maple is the material of choice for ribs. Maple is light, but stiff, and can be carved down incredibly thin before its resistance to pressure is compromised. For viola and cello, softer hardwoods can be used to good effect, but it’s rare to see anything but maple on a violin.

Using an electric bending iron, dampened ribs are pulled with strong pressure around its shape. The iron must be so hot that water dropped onto it bounces off in popping droplets, instead of flashing to steam. To reduce breakage, a strap, or bending caul is wrapped around to help put even pressure on the rib as it bends. I use flexible leather, although metal flashing and other materials are just as good. The lignin in the maple softens in the heat and pressure, and allows the maker to change the shape of the 1-millimeter-thick ribs to whatever the form and blocks imagine for it.


It’s a learning process to get such a straight-forward step right. Not hot enough, and the ribs crack and split, and are useless. Too hot and the wood chars even if it bends, and leaves ugly black scorch marks on the sides of the violin. Like baby bear’s porridge, you have to get the heat for bending ribs just right. All of that to bend some ribs into rounded shapes!

With some practice, and a few pieces of maple turned into kindling, a violin maker can determine the thickness of a set of ribs, bend them, and glue them to the blocks in his or her form in a few hours. It’s only the hundreds of hours spent getting that ease of practice that can fool the onlooker. 

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This article originally appeared in the May 2018 issue of Strings magazine.