Re: New platinum book & miscellaneous

Mike Ware (mike@mikeware.demon.co.uk)
Sun, 11 Dec 1994 16:37:37 +0000

On 11 Dec, Luis Nadeau wrote, re David Fokos' procedure for "invisibly
glossing" Pt prints with Liquitex:

>I would try gelatin as a substitute, fully hardened afterwards. It
>certainly won't be as convenient to use, of course, and platinum does not
>necessarily like gelatin. Mike Ware may have something to say about this.

So how can I decline an invitation from Luis? Here is the something:-

The platinum/gelatin antipathy that I have studied, occurs when the
*sensitizer* is applied to a gelatin-sized paper. Gelatin binds strongly to
the tetrachloroplatinate(II) complex, inhibiting the reduction step by
iron(II) after the exposure, which causes weak or 'fibrous' images.
However, the binding reaction is a slow one -taking some hours to complete-
and requires the presence of moisture; so if a platinum-sensitized,
gelatine-sized paper is dried completely and immediately on coating, the
binding reaction cannot proceed far, and image formation is not seriously
inhibited. Hence the C19th adage "water is the great enemy of the
platinotype" - it's not the water, it's the gelatin that is the enemy.
Avoid it, and you can leave the paper humid.

None of this, of course, is relevant to the matter under present
discussion, which is the stability of gelatin in the presence of *platinum
metal*. There is no direct reaction between the two, but it should be
remembered that finely divided platinum metal is a formidable catalyst. It
is possible that it might hasten the degradation of gelatin by other
substances in the environment, but that is speculation - I am not aware of
any work on this topic. There is also the question of what hardener to use:
the traditional papermakers' use of alum is now frowned upon for good
conservatorial reasons, and formaldehyde is a rather noxious substance for
'home chemistry'.

Having said all this, it hardly applies to David's prints anyway, which are
mostly composed of palladium; and their behaviour towards gelatin may be
different again from platinum.

Finally, a personal view: the purity and simplicity of platinum/palladium
prints is one of their attractive characteristics; the fewer additives the
better.

Mike