Another egg question, one I'd love to do scientifically sometime (this applies to anything where they suggest cooling with an ice bath).
Is an ice bath important? I'm pretty good with basic, practical thermal dynamics, it is analogous to electrical Volts, Amps and Resistance, so easy for me to translate. Assuming you have reasonably cool tap water (I know some places in the south do not at some times), it seems to me that
a flow of cool tap water might be better than an ice bath.
I've been through these discussions with home brewers trying to get their boiling wort (raw beer) chilled to yeast-friendly temperatures. There's a lot of myths and misunderstanding out there.
Water movement can have a very big effect on removing heat. Now, since ice floats, you will have some convection currents - the hot water rises, gets chilled by the ice and sinks. But that is much milder than a running tap.
Even if you use an ice bath, I bet the best fast chill would be to use running tap water to take the initial heat down, and
then put them in the ice bath. Brewers also do this if they need ice for the final step of getting the wort below their tap water temperature. The physics to this is, when that egg is really hot, say ~ 180F, there's little difference between that and tap water, and that and ice water. Using ice for the initial chill is basically just melting the ice, and warming the ice bath. Sometimes, the ice isn't melting fast enough to keep the water temperature from rising. When they talk about using an ice bath to calibrate a thermometer, they usually recommend ice chips (lots of surface area to melt), and a high ratio of ice to water. Or, it needs to sit long enough to stabilize, but we want to chill fast, right?
180 - 70 tap water = 110 F delta (but more water movement)
180 - 33 ice bath = 147 F delta (but might not stay at 33 with hot eggs in there?)
As the egg cools the advantage is greater for the ice bath, and the ice bath will help at some point. But maybe it doesn't matter much, maybe the initial cooling is all that is needed to help peeling?
A simple egg.
-ERD50