Stan, my point of view is that assumptons have to be made, such as, in open air where sunlight is available, it is reasonable to believe that oxygen and water in the form of humidity, are also available.
Craig, yes, but to my way of thinking oxygen and humidity (moisture/water) can also present in the absence of sunlight, can they not? And, oxidation can and does happen in the dark, if oxygen and water are present. So, what does the sunlight add?
To wit, even though a forend iron has been devoid of nearly all light, under the barrels, and sustains high levels of case color, it was never deprived of oxygen and moisture, except ............. by a light coating of rust preventative oil. Had the oil not been present as a moisture barrier the oxides would have formed anyway, without light.
So, back to square one for me; what exactly is it that sunlight itself can do to the surface of case colored steel that can transform the prismatic surfaces?
