Hi Rui,

I have no experience of them myself, but some photographic studios in the late 1850s/60s or so used to have them set into the roof, geared to follow the sun. Here is a thread from the Civil War re-Enactors wetplate forum (very interesting place) by Scully & Ostermann you might find interesting:

http://www.cwreenactors.com/cgi-bin/...rum=DCForumID1

The first solar enlarger (1857) could print an enlarged portrait in about 45 minutes, hence the need for the enlarger to follow the suns progress through the sky.

There is also a reference on the Alt-Photo list that mentions that Thomas Eakins (1844 - 1916) made direct 11x14 enlargments in platinum from half-plate negatives, so it should be possible to get enough UV out of one - given enough time!

Regards,
Neil.