> Re spotlights: different colored strings will react differently. Coincidence?
Plausibly not a coincidence. Different colors absorb radiant heat differently. For example, if you want to stay cool in sunlight, you'd wear red or white clothing, which reflects infrared.* Conversely, to get maximum heat our of sunlight, you'd wear blue or black. Although a higher temperature (known informally as "heat") itself probably does not make a gut string expand, it does drive moisture out of the string. And, in the case of nylon, it might act more directly. Practically, if you wanted to make a thermal protective sleeve for your instrument case, the silverly stuff people put in the their car windshields would be a good choice of material. It would be a good choice even when there was no direct sunlight, like in a hot car trunk where there is still lots of ambient infrared literally shining out from the hot metal. In Googling the subject, I even found a California regulation in the works dealing with car color, its effect on air conditioner power consumption, and the resultant effect on air pollution (ie, no black cars in California). Physically, the phenomenon is described by saying that the frequency of infrared light and microwaves corresponds to the resonant frequency for the molecular vibratory motion which is heat. You can pursue further reading by looking for the physics terms "radiant heat" and "bremstralung". To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
