RE: (long) Re: Permanence of Bleached Silver Prints
Richard Knoppow (dickburk@ix.netcom.com)
Thu, 19 Feb 1998 06:19:15 -0800
At 01:49 PM 2/19/98 +0100, Ole Chr. Magneshaugen wrote:
>The SilverLock toner was a sulphide toner, developed at IPI, with permanence
>as its main objective. I have seen data on test, where different films and
>paper have been treated in different toners and procedure, and the
>SilverLock really had something going for itself. The SilverLock outrated
>all other procedures by far. Selenium came out very poorly, especially at
>the dilutions usually recommended. Areas of little silver density are
>hardly affected by selenium at high dilutions. The SilverLock yielded equal
>toning effiency througout the density scale.
>
>Obviously the SilverLock is no longer made by IPI, due to availability of
>the liver of sulphur which was an important compound in SilverLock.
>
>In the report I am referring to it was interesting to see how much poorer
>the TMAX withstood ageing in comparison to traditional films, and even
>modern T-grain films from Ilford.
>
>If anyone has knowledge of research of thiocarbamide as an toning agent, in
>terms of its permanence raising characteristics, in relation to sulphide
>toners, I would like to know about them. Thiocarbamide is mentioned as an
>archival toning agent in several resources, but it would be OK to see actual
>test data.
>
>best,
>
>-olec
>
>
Again, it would be useful to know where this stuff is published.
If Silverlok is a sulfiding toner using liver of sulfer is is probably
similar to Kodak Brown Toner which is a poly-sulfide toner. Suposedly the
most archival toner is a combination of this type with Selenium. This is
put up commercially by Kodak as Kodak Poly Toner and by AGFA as Viradon.
All of these toners are used to tone to completion as are the usual Sepia
toner. Selenium would offer greater protection if used to tone to
completion but it is usually used where no or little color change is desired.
I had heard nothing about T-Max being more vulnerable than other films.
Perhaps it is because of the greater area exposed to attack due to the flat
crystals.
I have seen mention somewhere that Thiocarbamide toned images are not as
well protected as those sulfided in other ways but there was no indication
of anything quantitative and I now do not remember where I saw it.
This is all probably way off topic here as it applies to conventional
printing materials.
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com