Here are a few clues as to what to look for in a used violin bow.

1. When you first pick up the bow, sight down the stick to see if it is straight.
It's not too much to ask for a straight stick. If the violin bow is warped or kinked even a little bit, move on to another one.

2. Place the bow with the hair completely loose against a flat surface, like a table top. Let the frog and the tip rest against the table. Notice if the middle part of the bow also touches the surface. It should rest against a flat surface just as the bottom of the frog and the bottom of the tip do.

If it doesn't, that means the bow has lost some of its camber. (The camber is the curvature of the wooden stick.)

Camber is put in by heat and pressure. If a bow is not completely loosened when it is not used, when it is put away, then it will lose the camber. This is not good. It weakens the action of the bow.

When your candidate bow passes these two tests, and when you also like the appearance of it, try it out with a favorite tune.

Does it help produce the sound you expect to hear? Is it about the same as the bow you already have? Does it seem to fight you a little bit?

Be sure to play a jig, too. The varying amounts of bow used in the typical jig give a good chance to observe the responsiveness of the stick.

Does it move back and forth easily with a steady tone?

By the way, while you are making this evaluation, be sure the bow has enough rosin for a fair trial.

There is a particular test that I discovered by trying the bows of my students. For this, you should position the bow from the half way spot to the upper third, the one nearer the tip.

You just bow back and forth with small strokes, maybe 4 to 7 inches, and use a strong accent at the beginning of each stroke. You do this at an easy walking pace, not fast.

An unstable bow will "wubble." (Yes, I made up this word.) It will start to rebound repeatedly from the accent. It bounces and is unstable.
That's more than annoying. It's ruinous to your playing. A good bow is stable. When you apply a strong accent anywhere in your stroke, it instantly recovers and allows you to keep playing as you like.

If you have to fight to regain control, it is not a stable bow.

If you are buying a new bow, all those points still apply. The saving grace is the integrity of the company that is selling the bow.

My recommendation on bows used be, "The best bow for the money is a carbon fiber composite bow just under $200."

I don't feel so comfortable with that rule any more. I had the belief that those bows were like tennis rackets. The factory churns them out, one just like another. Experience showed that there were differences in the same kind of bow.

Try out this kind of bow the same way. Compare it to a good wood bow in the same price range.

Reputable dealers like Shar will let you try a bow before committing money to it. Your local music store may also have the same policy.