We all know that rosin is the main cause of friction on a string-instrument bow, but it also seems to have other properties.
For example, when I have a good coat of rosin on my bow hairs, they tend to break less easily.
Also, I had been noticing that my bow hairs had been loose. I owed it up to the cooler, damper weather that we've been having here. I would try to tighten the hairs, but the screw would already be all the way taut, even though the hair touched the stick with hardly any pressure. Then I applied some rosin half way through a practice, and as soon as my bow was back on the strings, it was tighter. So I loosened it and applied more rosin, and now I have the bow's full range of tightening back.
What exactly is it about the properties of rosin that make this happen? Is it just my imagination that this happens?