How tight to tighten a bow and its effect on tone production.

How tight do I tighten my bow?

Believe it or not, I get asked this question a lot. I’ve also heard a lot of interesting things such as “enough to fit a pencil through”. Now this statement is okay for a direct beginner as a rough guide, but I feel another better general rule should be adopted.

 

Torsional Waves and Slip-Stick Motion

There are plenty of good articles that expand on the physics of the bowed string:

http://newt.phys.unsw.edu.au/jw/Bows.html

http://newt.phys.unsw.edu.au/jw/torsional.html

When a string is bowed, there is a combination of slip-stick motion. As the bow pulls the string, it is stuck to it, moving it a specific amount. When the string has reached its limit, the string slips off the bow and swings back the opposite direction. Hundreds of slip-stick phases occur in a single bow stroke.

When you pluck a string, you create a wave in the plane of that of the pluck. However, when you bow a string, you do not only create motion in the plane of the bow stroke, but one that is more rotational along the length of the string. Thus essentially causes a spiral motion in the string.

Lastly, with the violin laying down on its back, the top vibrates up and down. There is little motion in the plane of the top but much in the plane perpendicular to the top.

 

So What does this mean!?

With the hair really tight, there is less grip on the string than when it is loose. With less tension on the bow, the hair can wrap around the string more, essentially allowing for better “stick”.

All variables remaining the same, except bow tension the following can be concluded.

With the stick really tight, there is more “slip” motion happening more often, causing smaller waves in the vertical direction, this in turn causes less vibration to the top: No Tone

With the stick really loose, there is more “stick” motion happening, causing larger waves in the vertical direction, this in turn causes more vibration to the top: Good Tone

 

What about volume?

Volume is not a function of pressure alone, but a combination of bow placement, speed and pressure. An amount of pressure is required to initially excite the string, to get a good attack, a clean and clear start to the note. After that, much of the volume is determined by bow placement and speed. So pressure should not be solely used to produce volume. I find many players use too much pressure and bottom out the bow against the hair and strings. I’ve seen a good many of bows where the corner facets on octagonal sticks have been rounded out just by playing. If bows were meant to be bottomed out then I’d humorously imagine they would have been designed with a replaceable brass plate on the lower three facets. Basically, this is to be avoided at all costs to prevent irreparable damage to your bow. 

 

So what do I think?

I feel that bow tension should be more organic, not one specific tension but adjusted to suit the many styles of music and playing. Next time you see a soloist, watch how much they adjust their bow, though there may be other reasons as well, but you will catch them adjusting the bow, between movements, sections, and sometimes phrases. Something more aggressive requires, more tension on the stick. Here, some tone is sacrificed to produce a barrage of energy with quick and loud playing, where the attack of the notes are more important. The stick is loosen for more “romantic” parts, where tone production is crucial. Many players will have more than one bow for different repertoire. Some bows can handle the brut force of aggressive pieces while others do not, but instead excel on the light and romantic repertoire. For the sake of the bow if you continually bottom out your stick, change your technique or get stronger bow. 

To put all of this into one idea:

Keeping the hair as loose as possible with enough tension so that the stick does not touch the hair when playing.