Bridges are a very important piece of the the violin family instruments. Bridges allow the vibrations from the strings to be transferred to the large resonating body of the instrument. They also hold the strings away from the fingerboard at the proper height for playing. Bridges are made from maple with very tight annual growth rings. The best bridgewood grows high in the mountains where the winters are long. The wood for bridges comes to violin-makers as “bridge blanks” with some of the intricate carving started. This is to save time, but carving a bridge is still very labor intensive because every surface must be worked to its final shape.
Paramount to the function of the bridge is how well it fits with the top. The “feet” of the bridge must conform exactly to the shape of the top, which can be complicated on some older instruments. This is achieved by putting a light coating of some colored substance on the top in the area of the bridge feet (some people use carbon paper, or graphite, I use a red watercolor pencil) and then placing the bridge on the top. Wherever I see color the feet are making contact. I remove the high spots with a sharp knife and mark again. When I see color everywhere the job is done.
Because all the sound from the strings travels through the bridge it has a profound affect on the final tone of an instrument. It’s almost like a filter or an effect peddle on an electric instrument. Like everything on the violin the bridge must be light and strong. It must have just the right amount of flexibility. The basic structure of a bridge is a “X”. One can remove wood from all around this “X” and still retain a large amount of it’s strength. We call the cut-out in the middle the “heart” and the two holes on either side the kidneys. How much wood you remove affects the weight of the bridge and also the stiffness. Where you remove the wood from also affects the stiffness.
In addition to its technical duties, a bridge must be beautiful. Every maker or shop has their own subtle style to how they carve a bridge. When it is done well a bridge can last decades. There are many fine old bridges from the Hill shop still floating around.