Hello Alan,
i was also surprised that coffee is frequently used for that purpose. I guess the reasons are is that it is readily available, requires no safety measures, and can be disposed off in your kitchen sink.
Of course results are more consistent using new blades with well defined steel combinations (e.g. 1.2848 and 75Ni8).
Nevertheless, i thought i would give it a try and share the results
@Rasdan
Buying a ton of FeCl3 would probably be no problem anywhere in the world (especially in Malaysia with its electronics manufacturing industry), getting it in small quantities is more difficult.
Here in Germany FeCl3 is available in small quantities at electronics retail stores for PCB etching. But with PCB services becoming less expensive this is a dying hobby. I don't know if there are such store in Malaysia, but i am sure these guys know if there are:
http://www.marts.org.my
Best Regards,
Thilo