While I am a baking amateur, weather and climate is my specialty -- and
your oven is nothing if not a micro-climate! So...here is my 37-cents on
the oven steam debate:
Just because you don't see or hear it doesn't mean it ain't there! The
hissing of spray hitting the wall or ice in a pan is reassuring, but the
effects of such small amounts of water is fairly close to negligible. The
ice cannot sublimate fast enough to raise humidity levels significantly,
unless you use enough ice that you lower the overall oven temp. Spraying
the oven and walls while the door is open means you are losing both
significant heat AND almost all of the (arguably) insignificant steam you
are producing. Do this several times, and I would argue any oven spring is
being caused by baking at a lower temp for the minutes that you repeatedly
open the door to spray.
I would suggest that the best way to introduce the highest level of
continuous humidity to your oven (without installing steam injectors) is to
use a wide vessel, such as a 9x13 cake pan or a quarter-sheet pan or a
14-inch oven-safe skillet filled 1/4 to 1/2 with *HOT* water. This way you
have a large surface area that is evaporating and producing steam the
entire baking time (if you wish to reduce the humidity during the latter
half of baking, covering is faster and safer than trying to remove!).
Joe