"Tim Williams" wrote: Here's the deal. Take a piece of iron. It has a
perfectly clean surface, I
mean the oxygen and nitrogen molecules of the air are bouncing directly
off the pure iron ......
^^^^^^^^^^^^^^^
I followed your explanation with great interest. You seem to take me back
to some the beliefs I held originally, and abandoned briefly as this thread
unfolded. I take it that you do not agree that a certain color on the
surface is correlated with a certain temperature in the metal. As I thought
originally, the color DOES correlate with film thickness, which, in turn, is
dependent on the time/temperature history.

Since "drawing the temper" of steel, as done by blacksmiths, using the
surface colors, is a way of raising the steel to the desired temperature,
why does it work? Wouldn't a longer time at a lower temperature produce the
same interference colors as a shorter time at a higher temperature? Could
it be that the time/temperature history produces the same effect on color
that it does on hardness? Or am I completely off the track here?