Every Time You Play
Always give your bow hair a few long swipes of rosin whenever you take your instrument out of the case. If you don't use rosin, your bow will be slick, and you will get a poor, weak sound. Don't overdo the rosin either. Too many swipes will give you a scratchy or whistling sound and will deposit more rosin dust on your violin. If the rosin starts to build up on your hair and become a little
gooey, you can use a clean toothbrush to remove the build-up. Buy a good cake of rosin. It will last for years and provide a consistent resistance to create a beautiful sound. Rub a new cake of rosin with a little fine sandpaper; do not scrape with a hard utensil/tool, and especially NOT with the screw of the bow. Don't lend your rosin to someone else. Nine times out of 10, you will end up needing to replace it!
Tighten your bow to the correct tension. Generally, for all bows except a German bass bow, the distance between the bow and the hair at the middle of the stick should be the same as the thickness of the bow stick. There should be a curve in the middle of the stick towards the hair. If you tighten your bow more than this, your bow will be too straight and will lose some of its performance, and it will be more difficult to play some strokes, such as spiccato, which require the bow to bounce.
When you are finished playing and are ready to put your instrument in its case, loosen the hair, so that there is no tension on it. This will help keep your bow from warping. Also, wipe any rosin dust off your instrument, strings, and bow stick with a soft cloth before you put them in the case. If you don't, the sticky rosin dust will build up into a crust that will harm your sound and damage the varnish.
If you must put your instrument down, always put it in its case. Never leave your instrument on a chair, a table, a couch, the floor, or hanging by its scroll from a stand. We have seen a number of accidents that easily could have been prevented by putting up an instrument in its case. Don't let someone
try your instrument. No one is ever as careful as you are with your own instrument.