Luis probably isn't up yet so I'll give my answer. Of a kind.
Find somewhere or someone that has a good collection of prints made by
the different processes that you can hold and study. (If anyone in the UK
reads this, perhaps the RPS collection or the V&A Museum?). It is no good
looking at reproductions - you need the real thing.
This will convince you that carbon is worth the effort. And mess, and
time to make your own tissue. Only reason I don't do it at the moment is
that I have to earn a living and would like to remain married. And also
because the actual taking of photographs is still my major focus.
Carbon can give much more 'photographic' results than gum - much better
tonal gradation and more detail. In part this is because carbon solved
one of the inherent problems of gum - that the hardening by light occurs
on the surface of the gum layer first.
Peter Marshall
petermarshall@cix.compulink.co.uk