Thread: Re-hardening a vintage razor?

Originally Posted by Utopian

So these were not previously honed by someone else and then used by you?

Are you confident in the skills of the honer who judged these blades? The larger two blades' photos do not appear to have come close to a set bevel.

I think that they are before photos

There are anecdotal reports of steel blades (old swords of legendary quality being tested later to find they are not so legendary) losing their hardness. But, the blades referred to are centuries old. Essentially hardening steel introduces energy into a crystalline structure that is then subject to the disorder of the laws of thermodynamics. I doubt any of us will live long enough to test this proposition. We can't go back in time to hardness test old steels and then leave them so we can test them later to know. It's an interesting thought problem though.

I have rehardened newly ground wedge (8-12 inch diameter wheels) style razors using controlled temperature salt baths. Definitely a style of grind with a radius to the edge not a flat blade with a tight radius at the spine. I knew everything about the heat history of the material through making the blades and coordinated the efforts with those grinding them. Two thirds of those potato-chipped along the edges up to about 200 thousandths. The resulting blades were hard, but had moved from 8/8ths to 6/8ths. About a third could be predicted to remain with a stable edge. I have not attempted vintage blades except Herders and those were not near a finished edge.

For the most part, I would not recommend attempting to re-heat treat a vintage blade or one that had been taken to a finished grind (pre-bevel set). It can be done, but should not be without the expectation of losing some of the blade width in the process. Luck is simply a variable that cannot be denied.

Color changes from overheating can be polished away. There is a legitimate question about honing technique that has not been resolved in this discussion or subsequent evaluation of the blades. Still too many questions.

Originally Posted by edhewitt

I think that they are before photos

Thanks that makes a lot more sense.

I still find it very strange that 3 vintage blades were judged to be too soft at the same time.

Honorakr, would you please clarify what sort of light cleaning and restoration you did? I'm wondering if you did anything to alter the temper of the blades.

Honestly do not think there a many Vintage blades worth the time,effort, and money that would warrant being re-hardend,JMO