Re: POP prints archival ?

John Rudiak (wizard@laplaza.taos.nm.us)
Sat, 4 May 1996 14:45:41 -0600 (MDT)

On Thu, 2 May 1996 SCHRAMMR@WLSVAX.WVNET.EDU wrote:

> No reason why it should be any better or worse than any silver print.
> POP paper contains silver chloride. Modern papers are a mixture of
> silver chloride and bromide. But the significant condition is gold
> toning and washing. Once the paper is exposed, developed and fixed the
> image is made of silver grains. It maters not if it started out as
> silver chloride or silver bromide or for that matter, silver iodide.
> The gold attaches itself to the silver grains. Gold is less reactive
> than silver. A really good washing gets rid of the hypo.
> BTW most photoarchivists consider selenium toning as good as gold toning.
> Properly fixed, toned and washed silver prints shoul;d have a lifetime
> of 100-300 years. Some RC papers are now being accepted as archival
> e.g. Ilford Multigrade IV Deluxe.
>
> Bob Schramm
>
When toning in a gold chloride bathe, the gold actually replaces the
silver, rather than coating it. When the toning bath is alkaline,
changing the auric salt to the aurous salt, the gold replaces the silver
in a ratio of three atoms to one, which explains why there is somewhat of
an intensification.

The increase of archivality of the toned print can be explained by
comparing the toned silver grain to an M & M, the silver being the
chocolate and the gold being the coating which makes the M&M melt in your
mouth, not in your hand.

John.