Magnetic Ink?

One of the pieces of spam in my mailbox today mentioned selling "magnetic ink"
for use in printing the MICR line on blank check stock. Since I have a policy of
immediately deleting spam, I obviously did not go to this person's web site.

I am curious though. The inability of most banks to read non-magnetic coding put
a quick end to my experimentation with printing my own checks. Has someone
developed black ink with fine enough particles so as not to plug an ink jet
cart, or was this guy blowing smoke?