I started brewing back in may, at the beginning of a Californian summer. I quickly learned that the swamp cooler was necessary to prevent unwanted ester formation due to a too-high of temperature for a given yeast. The swamp cooler isn't good enough, however, and requires substituting frozen water bottles 3x per day. This is absolutely excellent for keeping a ceiling on the wort temperature. However, the temperature swings beneath the ceiling can be pretty severe. For my current 4 batches going, I have put the ceiling at 66, but temperatures vary widely from 57-66, 24 hours per day.
I hear from this forum and others that temperature swings are also bad (that it will stress the yeast).
What is the reasoning behind this? I.e., too high of a temperature causes ester formation. Ester = off flavor.
Do the temperature swings, even with a ceiling on temperature, cause off flavors? Why. If they don't cause off flavors, why are they bad (other than swings that would cause a decrease in attenuation for going too low)? The swings are no doubt superior to ester production from too-high of a temperature, correct?
I would imagine that with a ceiling, a swing of 20*F would be bad as it would cause a lower attenuation. So for the second part of my question, lets add a theoretical floor to whatever temperature gives the maximum effective attenuation for a given strain. In this circumstance, with a ceiling (to prevent esters) and a floor (to retain attenuation), why would swings be bad?