Arching

 

There are an infinite variety of archings, probably as many as there are makers, because even with a set of templates copied from an original instrument some variation is inevitable.  The earliest arches were the simplest: a straight up and over design or catenary curve, which is the curve that a chain makes if hung between two nails.  Arching became increasingly complex in its curves in the 1600s and then simplified again in the 1700s with the work of people like Stradivari and Guarneri, who by then had several generations of violins to study and could pick out what they thought worked.

 

The major job of the arching is to make the violin strong enough to withstand the weight of the bridge and strings by spreading their force evenly over the front.  It is estimated that this force may be equal to as much as 13 kilos.  The front and back of a violin are carved from solid wood using gouges, and then, when the gouges can do no more, small brass planes called thumb planes.  The instrument is then carefully finished off using thin steel scrapers, which are shaped to follow the violin's curves.

 

After the arch is formed, the plate is then pierced with sound holes. This considerably weakens the structure, which is then given additional support by the insertion of a bass bar and a sound post.  The bass bar is a beam of wood carefully fitted under the bass side of the violin bridge and running roughly at the angle of the Gstring. The sound post is a moveable pine dowel fitted just behind the opposite bridge foot.

 

Some of the mass produced French violins of the late 19th century have pressed plates.  Thin sheets of pine, or maple for the back, were steamed to make them pliable and then pressed into moulds.  This was an attempt to speed up the making process and create a cheaper product.  Some of the pressed instruments can work very well, much better than expected; some don?t work at all and can sound very uneven.

 

Arches can rise straight from the edge, or can scoop a long way in.  They can be flat or curved, high or low, scooped or not scooped, and each maker, country and time has their own preferences.

 

Arching is a major component in sound production, but it?s not the only one.  The thickness pattern used, the size and position of the F-holes, the proportions and placement of the bass bar and sound post, the neck angle, bridge shape and fit, and the style of stringing all have important effects; all these impact upon the arch and modify the sound it produces.

 

As a general rule a highly curved arch gives a "softer" or even, in extreme cases, a "hollow" sound, and a flat arch produces a stronger, punchier sound.  You can see how this happens if you think of Rolf Harris and his wobble board.  If you flex a thin sheet of metal or plywood back and forth, it creates a pulsating sound.  If the sheet is curved it would not return to, and pass through, its original state, and very little sound would be produced.  In the same way, a box van rattles if it goes over a bump, but the flowing curves of expensive car damp down the vibrations and you get a quieter ride.

 

High or low, the mark of a good arch tends to be whether the curves flow into each other cleanly, without sudden changes of direction.  If the curves are abrupt, the arch is stiffer, if the curves are smooth then there is a greater chance of enhanced tone production, given all the other variables mentioned.