Esters can be produced in many many ways. One of the most important is uncontrolled yeast growth at the beginning of the fermentation. As a consequence, I usually pitch at a few degrees lower than the steady state fermentation temperature because I have found the bad ester / nail polish tones can be very quickly formed from elevated temperatures at the very start. Ironically, we have also seen extremely high O2 levels (typically, when excess oxgenation of the yeast as opposed to the wort has been used). We are all concerned about lag times and correctly so. But, as far as esters go, I would prefer a "soft" start. more Where the fermentation may take up to 8 hours to get going, because of the initially low temperature. end