what is the difference between light and dark rosin?

Question

and what would be recommended for a viola?

Answer 1

Q: "How often do I use rosin and is light or dark better?
A: Rosin should be applied to the bow whenever needed, but typically after 2-3 hours of playing, a light coating is recommended. You will need to apply more rosin to a bow that has been freshly rehaired.

A few things to remember: Do NOT swing your bow in the air to get excess rosin off the hair. It typically does not get any rosin dust off the hair, and you run the risk of hitting the tip on a solid object. Also, the mere quick swinging of the bow could snap the stick at the tip.

Dark rosin is typically softer and stickier than light rosin, so many cellists use dark to give more bite on the string.

http://www.cello.org/ietips/rosin.htm

Answer 2

Bassists also use dark rosin.

But, for a viola I would recommend light rosin.

BASSES RULE!!!!!!!!!