Dounis said that most string players 'don't realize that the technique of Up Bow is very different than the Down Bow.'
So... What's the difference?
Here's a breakdown...
1. On the Down Bow the direction of the pressure and the line of the pull are different.
It may be obvious to many that you are pulling the bow horizontially to the right but your pressure is vertical.
2. On the Up Bow the direction of the pressure and the line of the pull are the same.
The Up Bow is surprising because you're pulling the bow horizontally to the left andyour pressure is horizonal to the left.
3. The bow change at the tip is different from the frog.
As you approach the tip, the bow is already moving in an arc led by the hand, at the point of change the wrist reaches down as if it were going to a lower string in a clockwise motion.
As you approach the frog you're moving down the arc (or downhill). Then at the point of change, the bow is released.
4. On the Up Bow there is a slight firming or closing of the hand which is released on the Down Bow.
This firming and release is the close/open of the grip and it happens on every bow change. To get a feel for it pick up a large ripe tomato and squeeze it gently like you're testing the ripeness.
5. The Down Bow and Up Bow are on different string levels.
The Down Bow is on the lower side of the string and the Up Bow is on the upper side of the string.
These five points clearly show the differences of the Down Bow and Up Bow techniques which helps us to understand why Dounis wanted everyone to practice everything withreverse bowings while trying to make it sound exactly the same.