[Alt-photo] Mechanism for Platinum Enlargements

[Francesco Fragomeni]

Hi All,

I may have asking something along these lines a long while back but I'm
unsure. There also may have been a bit of conversations around this on-list
in the past. Anyway, I've always been fascinated with the old methods for
making Platinum enlargements and I'm curious if anyone knows any of the
numbers (exposure times) or knows of anyone who's working (albeit slowly)
with anything like this now.

Despite common belief, making platinum prints through an enlarger is indeed
possible and there is a long history of this. As a quick recap, the most
common method was through the use of a solar enlarger attached to a
heliostat. The solar enlarger was essentially the same as a modern
enlarger, most commonly using condenser lenses but there is documentation
discussing diffusion solar enlargers as well, and lenses that were good at
passing UV light. The heliostat was a mechanism that allowed the enlarger
to track the movement of the sun subsequently keeping the light source
centered and focused throughout the printing.

Much later Durst made a UV enlarger for Azo and supposedly had one in
development for platinum printing but it never made it into production.

Anyway, I've heard whisperings of people who's made platinum enlargements
essentially in conventional enlargers after replacing the lens with an
older lens that'll pass uv light (modern lenses tend to block uv) but I
can't really find any documentation of this. What I've heard is that the
super powered lamps as used in the Durst UV enlarger (5kw and requiring
serious cooling) are not actually necessary if you're ok with loooong
exposure times (into hours). The Durst was supposedly designed to make
these exposures both possible and relatively quick. I personally wouldn't
care if the exposure times were very long if this is something that could
actually be achieved.

Does anyone have any information/experience with this? Any idea of how long
exposure times would actually be if using a uv bulb or mercury bulb in a
diffusion or condenser enlarger?

Lets try to keep this on topic. This isn't intended as an opening for
recommendations to contact print or make enlarged negatives. This topic
isn't concerned with any alternatives. We're all aware that platinum prints
are conventionally made using contact printing. We also know about making
enlarged negs. No need to touch on any of that here. This is about the
feasibility, practicality, and possibility of making a platinum enlargement
via an enlarger set up to utilize uv light. We're also not tied to
attempting to attain short exposure times here. Long is fine. I'm
interested in tapping into the creative thinking of those on-list so lets
try to limit the "thats impossible" talk. We already know that platinum
enlargements are possible. Thoughts?