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You did not tell us what grade of diamond spray you are using
and you did not tell us how the razor shaves.

The truth lies in the shaving.

If you are asking and you are honing your own razors...

Black ink jet printer ink is not going to be carbon based
the way India ink or Asian brush ink is.

You can test it by diluting a bit and then let it wick up a strip of
paper/ filter paper. ...

graphite or carbon/ charcoal?

Straw especially rice straw has a silica component that
is available after burning..... At one time charcoal from
straw was considered an excellent strop...