I was reading some Alton Brown and he has this to say about pre-heating the
oven. IF you set the oven for a temp and it dings and tells you it has
reached temp, it has. BUT when you open the oven door, much of that nice
hot air will escape. IF you're baking something that must have the correct
temp, you need to pre-heat for at least 20 minutes. That way, the oven's
floor, walls, ceiling, back and assorted other parts will be heated enough
to maintain temperature even after you open the oven door and insert the
'grand recipe'.
Of course, some of you already know everything but it seemed to me that
this might be helpful to those of you who are hoping to duplicate the
perfect cornbread, pound cake or meringue like Moma used to make. Polly