[pure-silver] Re: When is Sulphide toner not sulphide toner?

----- Original Message ----- 
From: "Christopher Woodhouse" <chris.woodhouse@xxxxxxxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, November 26, 2004 9:40 AM
Subject: [pure-silver] When is Sulphide toner not sulphide 
toner?


> Whilst it is well understood that sulphide toners protect 
> images from
> deterioration, when it comes to the odourless sepia 
> toners, like
> thiocarbimide, I'm assuming that the end product is also 
> silver sulphide.
>
> If it is silver sulphide, which we all know has brown 
> tone, why then, if I
> tone a fixed and washed print in thiocarbimide, before it 
> is bleached, does
> it have a marked effect upon subsequent bleaching and yet 
> has NO visual
> effect on the image?
>
>
> -- 
> Regards Chris Woodhouse
>
>
  I am not sure why this is but the same thing happens when 
using sodium sulfide. If the print is soaked in the sulfide 
bath and rinsed before bleaching it affects the final color.
  The color of the toned image is not due to its being 
sulfide but rather to the effect the sulfiding has on the 
shape and size of the silver particles, which in turn is 
affected by the orginal crystal morphology. As an example 
polysulfide toners tend to shift microfilm toward blue 
rather than yellow. AFAIK this has no effect on the 
protective properties of the toning, but there is no 
research data to show this. The problem with all odd toning 
processes is that one must assume certain things about it. 
Certain toners have been tested in accelerated aging tests 
so their effects are known with some degree of certainty, 
for others its partially guesswork.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

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