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

The question remains:

Can one use thiourea (thiocarbamide) instead of polysulfide for direct
toning and get the same archival properties? I only considered them for
indirect toning. The lack of odor would be reason enough, the lack of color
change another benefit for many. Why are we still buying polysulfide toners?





Regards



Ralph W. Lambrecht




On 11/26/04 6:55 PM, "Richard Knoppow" <dickburk@xxxxxxxxxxxxx> wrote:

> 
> ----- 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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