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It's often hard for experienced players to explain problems that less experienced players are having. I presume, because those issues are so far in their distant past that they only dimly remember them. Now that their technique is perfected and stored securely in muscle memory, they never have to give it a thought. As a rank beginner I'm having to overcome all of the issues beginners have, including bow bounce.
Here is what I have observed (and again as a rank beginner you can take it or leave it,) and I could be way off base. Consider a young driver trying to learn to drive a stick shift. Invariably they will press too hard on the gas and let the clutch out too quickly. When that happens the car lurches forward, the tires chirp repeatedly on the asphalt as the tires alternately loose traction and regain it, then the engine dies. Dad becomes frustrated and tries to explain how to let the clutch out slowly as the gas peddle is depressed smoothly. Then they repeat the process, until eventually the youngster can do both things smoothly.
The same thing happens with a violin bow. The middle of the bow is the bounciest part. When too much downward pressure is applied to the bow and/or the movement is too slow or too abrupt, the bow hair digs into the string, bends it, then suddenly breaks free and bounces on the string like tires breaking free on asphalt. This also happens very often when crossing strings, from the A to the D for example.
Having determined the cause, what is the solution? What I have observed (and again I'm just a rank beginner, but I've watched a lot of videos) is that there are two (maybe three) primary factors at play, similar to the clutch and the gas pedal. One is the grip. If your grip is correct and the pinky is on the top of the stick and flexible, as it is supposed to be, it will act as a shock absorber and reduce the ability of the bow to bounce up and down.
The second is the bow stroke (and this is the hard one.) Since we are talking about the upstroke, if one pushes the bow with the hand and/or arm, one (or at least I) will get a bow bounce. To mitigate or eliminate this problem I will refer to the Karate Kid metaphor of "Painta Fence. Upa, Down, Upa, Down. Vellly Gooo Daniel san." It seems to be very important to remember that the movement of the bow stroke is choreographed by the wrist, much more than the hand or the arm. They move, of course, but the wrist is what is leading the parade. The wrist begins it's upward travel by flexing slightly and it pulls the hand behind it and the same on the down stroke. The wrist moves first and pulls the hand behind it. This seems to produce a much smoother acceleration eliminating bow bounce.
Lastly, if you watch videos of expert violinists you will notice that the bow rolls across the hairs from side to side as they bow. I imagine, although I am not certain, that this maintains a constant amount of friction as the bow accelerates across the strings. Starting with fewer hairs in contact with the bow at the beginning of the stroke will reduce friction, then rolling into full contact with the string once the bow is moving sufficiently and then repeating the process on the down stroke. Just like the clutch and the gas pedal.
I'll shut up now and let the more experienced players correct my impressions while I sit quietly in the beginners section.
A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. ~Herm Albright
@Uzi If I suspected that the bouncing bow issue was as complicated as your last post I would have been scared off. It seems that almost all students simply outgrow the problem and I guess you will too.
One (frightening) parameter you did not mention is rosin. Much of what you do with the bow involves quantity and variety of rosin. I do nothing right if my bow is suffering from low rosin.
When you come to a fork in the road, take it.