[pure-silver] Re: word from ilford
- From: titrisol <titrisol@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Tue, 14 Aug 2007 22:42:49 -0700 (PDT)
One of the advantages of the Ilford papers (not the Warmtone) is
that they tone poorly in Selenium, with almost no change in
color. Just that green tinge leaves for a richer gray scale,
also IMHO the contrast range is not affected.
AGFA MCC took a beautiful aubergine, and the Patterson papers
also toned well.
Ilford WT was the most interesting paper to tone since the range
of tones was variable depending on the developer. I used Ethol
LPD, and depending on the concentration (1+2 -> 1+10) the tones
went from brown-ish to purple, I assume this is due to the
different action of the developer which makes the images
warmer/colder to start with and that should somehow affect the
size of the silver grains to be toned later.
I was using patterson selenium toner when I tried all these
papers, but I assume kodak's would do more or less the same.
--- Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
> >
>
>
> There seems to be no research data on Sistan. It may
> very well work but I've never seen any proof. Fuji published
> a research paper on Ag-Guard, another stabilizer. Ag-Guard
> is different from Sistan so research on one does not
> necessarily apply to the other. The Fuji research showed
> that Ag-Guard was effective in protecting images against
> action by oxidizers but less so than sulfiding toners.
> Very dilute solutions of Kodak Rapid Selenium Toner do
> not tone all densities uniformly. While early resarch showed
> KRST to be an effective protective treatment it appears to
> have changed in some way about 20 years ago. After that
> change it was no longer effective in weak dilution. The
> research showing this was carried out by the Image
> Permenance Institute of the Rochester Institute of
> Technology. At stronger dilutions KRST is effective but will
> change the color or density or both of the image. The
> recommended treatment is at a dilution of not more than 1:9
> and for not shorter than 3 minutes at 68F.
> A better treatment is a liver of sulfur type toner such
> as Kodak Brown Toner. These toners convert silver uniformly
> regardless of grain size so partial toning will have some
> protective action on all densities. However, KBT does cause
> a color change on many materials. It, and similar toners,
> are now the recommended protective treatment for microfilm.
> Gold toners are also quite effective but are expensive.
> Gold toner produces a neutral to bluish image on neutral
> tone paper and a blue color on warm tone paper.
> Bronzing or silvering out is an effect of atmospheric
> oxidizers on the image. The convert the silver to a very
> finely devided Silver Oxide which then can migrate to the
> surface of the emulsion where some of it is converted back
> to metalllic silver by other polutants. The metallic silver
> can be yellow to silver in color depending on how finely
> devided it is. Silver oxide is black so there are also black
> stains on the surface of the print. These stains can often
> be removed but some silver will have been removed from the
> image so it may be faded.
> Metallic silver can also be sulfided from polutants in
> the air or in the emulsion. Usually, this results in a brown
> or yellow stain. Where there are sulfur containing compounds
> in the emulsion, such as hypo or fixer reaction products,
> the stain can be generalized, not just of the image. In some
> cases the stains can be removed but some techniques
> recommended in the past have been shown to accelerate future
> aging of the image.
> A very small residue of hypo remaining in the emulsion
> can act as a stabilzer by partially sulfiding the silver.
> This prevents further sulfiding or oxidation. However, other
> than not using very extended washing there is no
> recommendation and not much information is available about
> how much hypo should be retained. This effect has been known
> since about 1960. It may be one reason that some drugstore
> processed snapshots have survived in relatively good
> condition. It has been shown, however, that film and paper
> processed to the old standard of having no residual hypo is
> particularly vulnerable to oxidative attack, unless it has
> been toned. Sources of peroxides are plentiful especially in
> urban areas. For best life prints should be toned in a
> Liver-of Sulfur toner, a fairly strong solution of KRST (as
> indicated above), a Gold toner or fully toned in nearly any
> sulfiding toner where the resulting image color is not
> objectionable.
> In general, prints should not be covered by tightly
> fitting glass or plastic covers, especially RC prints.
> Note that in the past RC prints were subject to
> oxidation from a gas emitted by the Titanium Dioxide
> reflective layer beneth the emulsion. This effect was
> exagerated when the prints were mounted under glass or
> plastic, which prevented escape of the gas. This gas
> attacked both the image and the plastic layer causing it to
> craze and even flake off. Modern RC papers contain
> scavengers for these gasses and, in general, are about as
> permanent as fiber base paper. They will still benefit from
> proper protective toning or the use of stablizer.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
>
>
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