What are the different types of rosin, and which should I use?

Players of lower instruments generally prefer softer rosin, requiring more stickiness to move their thicker strings. Players of violin and viola may prefer harder rosin for faster bow speeds and ease of bow response. 

Dark rosin is usually slightly softer. However, one should not choose rosin solely on the basis of color since soft and hard rosin can be made in any color.

NOTE: Most players use too much rosin on their bow hair and rosin too often, resulting in a rough, gritty sound, and rosin build-up on their instruments. You can avoid this by applying only a small amount of rosin (3-4 swipes) at the beginning of every playing session. Wipe down your instrument and strings at the end of every playing session to avoid rosin build-up.

How to Rosin Your Bow