U of S | Mailing List Archive | alt-photo-process-l | RE: pt/pd mounting

RE: pt/pd mounting

The following is copied from Mike Ware's page at
http://www.mikeware.co.uk/mikeware/Eighth_Metal.html.  Hope he won't mind if
he finds out...


The third attribute -of permanence- had been a longstanding issue ever since
the Fading Committee of the Photographic Society reported in 1855, and the
Duc de Luynes' prize for a permanent process was won by Poitevin (for Carbon
printing) in 1859. Willis's platinum research was also stimulated by the
quest for permanence, but even after he had finalised his procedures, we
find many articles in the photographic literature complaining of incomplete
clearing, and offering suggestions for curing yellowed highlights in
Platinotypes. A modern investigation of this problem, and the extent to
which it can be attributed to residual iron, has recently been carried out
by Rees and Gent at the Victoria & Albert Museum (48). Although the metal
constituting a Platinotype image is invulnerable, its paper substrate is
certainly not. Acid embrittlement of the cellulose is the other besetting
problem that Platinotypes present to the conservator. The build-up of acid
is exacerbated by the catalytic action of the platinum black itself, which
assists the conversion of sulphur dioxide to sulphur trioxide and hence to
sulphuric acid (49).