In this recording of Jascha Heifetz he frequently tilts the bow inwards (by which I mean towards the bridge instead of "outwards" towards the scroll). Here's a frame showing it:
I have never seen this done before. Is this a known technique, with a known purpose? Is it used by any other virtuosi?
Heifetz uses a Russian bow-hold. This is almost never seen today in classical violinists and is more common in gypsy jazz. Some things are easier with a Russian bow-hold, you naturally apply more pressure near the tip, and some things are more difficult because you don't have any contribution from the fourth finger balancing the bow near the frog or when the bow leaves the string as in the staccato here.
Mischa Elman was another great from about the same time as Heifetz who also used the Russian bow-hold. Here you see him also tilting the bow the "wrong" way, showing the audience more of his bow hair.
A frame from Hora Staccato. Must be a reason for using this technique for this piece. If you watch this piece through, he also completely changes his bow hold when reversing the bow.
There is not need to do this when it's slow, it even is a mistake. But when very fast, to facilitate repetitive string changing, we tilt it when switching up bow to down bow. When doing this, make sure to not skid.
