Lauri of Finland has perfected the process to temper the spine to a
utilitarian hardness of RC52 while the edge is
hardened to an incredible RC63.
This process gives you a hard working blade that is not only durable,
but will hold a razor sharp edge longer
than anything you now own.
The Lauri PTX blades, with the
high definition tempering line, have been discontinued.
However, you can make your own.
Dip a Lauri PT blade in Nitric acid (5 - 10%) for 2 to 3 seconds.
Rinse with water and polish on a buffing wheel.