Here is an excellent article on all techniques of enamel photography and its pdf version for safe. I created from html file and few small pictures are lacked but all recipe charts are there.
''A number of readers have requested information concerning the procedure. There are several workable methods, each having some advantages as well as...
Thank's for posting the PDF file as the .nl site seems "tired".
A teacher of the school I work in has been very happy to know about it, as he's going to develop a course next year exactly about those processus (we have the ceramic oven).
I'll try to make him give some results of the thing around here.