Need help on selective tempering

[Mizar]

Hi to everyone!! I will appreciate any advices on how to make selective tempering of already hardened blade /it is made of high-carbon steel/ and to get a temper line. Is it possible, if I treat it with an acid /vinegar ?/, to get a decent line?
Thanks in advance!

 

[mete]

The line is usually done by differentially hardening, that is quenching the edge and letting the spine cool in air. That gives martensite on the edge and pearlite on the spine .The two structures then etch differently. To differentially temper you would still have martensite on the edge and spine. The difference in etching between the two would not be as great as the martensite/pearlite difference. You could give it a try, put the edge in water and slowly heat the spine with a torch.

 

[Mizar]

Thank you. I will give it a try!