Prior has been said and believed that the blade warping is caused by tempering.
But watching those videos, you can see that the warped edge is /or can be/ created by poor grinding after all. Possible cause is when the grinders hand isn't moving along straight line. Tempering cannot be a culprit, because after tempering the worker checks all rawlings and straightens them on anvil when needed.
What do you think about this conjecture?
Secondly, I want to ask if anyone knows or has used straight razor regrinding service? For example, I have several very good razors that are with wide bevels and bit to heavy hone wear on spine... as you may have them too. It would be nice to save them. I believe that spotting this Klaus Braun guy from Solingen cannot be very difficult or impossible task. Maybe we can act together... I will have very difficult to do this alone because my German language is poor.
Regards,
Urmas