I'd love some help as my teacher is stumped with this one. Sometimes when I play, I get alot of bow judder in the middle of the bow on a down bow. Particularly badly after a string change. Some days it barely happens at all, and sometimes like tonight it happens every down bow and affects tone. My bowing is straight and confident, (I use a mirror) and my fingers and wrist are relaxed enough to move with the bow. I'm getting really frustrated as I can't work out why it's happening, therefore cant' work out how to fix it. It's not the bow because it doesn't happen all the time. I have a wooden hexagonal bow, not sure of the make but it was valued at ?250 by cardiff violins and is about 20 years old. It has new hair on it.
If anyone can explain to me why this might be happening I'd be so grateful. I always do up to half an hour of slow long bow strokes and slow scales in the mirror, have done for months, to try and fix this problem....

Hi Kate,

When this happens to me, I am too tense. Try making sure your shoulder and arm are completely relaxed and let their weight bow into the string. And thumb....9 times out of 10 it's the thumb!

I used to struggle really badly with this, but it's improving well and it's all due to relaxation. Think carribean island when you play.....

It sounds to me like it might be tension.

Have you tried just ignoring it and seeing if it goes away after a while? I know it might sound daft to just ignore the issue, but if it is an issue to do with tension then it may well get more noticable the harder you try to solve it. (It irritates you, so you tense a bit more, so it irritates you more, etc...). I get caught in this if I'm not careful and it's normally my upper arm or shoulder.

Well, whadaya know! That's working. Thanks!
thankyou Sunrise, you talk sense! I've been "trying" too hard.