Tringo said:
I read somewhere that rinsing the razor, and therefore the blade, in cold water is beneficial.
Theory behind this, based on the universal law of Physics, is that if you rinse the blade in warm water it will expand resulting in it being 'less' sharp. Rinse it in cold water the blade doesnt expand and therefore retains a sharper edge.
Bollocks. If heat expansion, in this temperature range, had a significant effect on edge sharpness, many more relevant processes would suffer from this, and would either control cutting temperature variability, or hone edges at operational temperatures. Not even the knives of biological microtomes are treated this way... Err, not sure that that is actually a good example, but you get my point.
Also remember that the blade represents a tiny amount of material, with consequently a limited heat capacity. If it were only the blade, any heating or cooling effect from hot or cold water rinses would be negated by the heat absorbed from the skin in no time. Same with the lather -- whether warm or cold, the lather soon adopts the skin's temperature. During shaving the blade temperature therefore essentially is the skin temperature.
But wait, you say, you're not only shaving with a bare blade, there's also the rest of the razor. Correct, and that rest of the razor is so large/heavy that it won't change temperature much from quick rinses in hot or cold water. So whichever way you look at it, rinsing in hot or cold water will not significantly influence actual blade temperature during (much of) the shave.
I think that warm water helps in softening the beard (as in quickens it), and warm lather is more comfortable. Other than that, I don't think there will be a major difference in hot vs. cold shaving. Warm water/lather shaving works, and probably shortens the prep time, cold water shaving also works.
