Removing tool marks - Hydrochloric Acid

Quoted text begins.Once the edge turns bluish black the
temper is ruined, won't keep sharp and you might as well throw it away,
End of quote.

Don't throw them away! Send them to me ... I will pay postage! In fact, I
will buy the tools. It is not difficult to learn tempering of a tool. The
straw color that a heated tool takes just before it turns blue is, I believe,
the proper color for stone work. If a tool is overheated simply begin again
and quench at the proper color. Practice and a good book on the subject will
start you making those unusual shapes you always wished you could buy.
Philip Whitley