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

Thanks Richard, I thought I had read somewhere that Thiourea or
Thiocarbamide toners do indeed produce silver sulphide. Funny thing is, if I
dunk a print into the toner, after full fix and wash, it resists a ferri
bleach more or less the same as a 5 minute 1+10 selenium treatment.

Some users, who go for the sepia toning for effect, use this pre-tone as a
way of protecting highlights from any reduction in the bleach and
redevelopment process.

What I can't quite understand is, if a print is fully fixed and wash, what
is the toner working on in this first toning step?

Chris

On 27/11/04 5:33 am, "Richard Knoppow" <dickburk@xxxxxxxxxxxxx> wrote:

> 
> ----- Original Message -----
> From: "DarkroomMagic" <info@xxxxxxxxxxxxxxxx>
> To: "PureSilverNew" <pure-silver@xxxxxxxxxxxxx>
> Sent: Friday, November 26, 2004 1:34 PM
> Subject: [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
>> 
>  In a bleach and redevelop toner Thiocarbamide converts
> the rehalogenated silver into silver sulfide just as sodium
> sulfide does. It is as archival.
>  Indirect toners can not be used for partial toning
> because they don't tone all the silver. While this can be
> used to produce some interesting split toning effects it
> does not result in full protection of the silver image.
> Polysulfide toners, when the stock solution is stong enough,
> can be used for partial toning and tone all densities
> evenly. Some minimum part of the silver must be toned to
> result in full protection but any toning will result in some
> protection. The minimum probably varies with the material.
> According to IPI it is 60% for microfilm. The degree of
> toning is found by bleaching out the silver image with a
> dichromate bleach and measuring the density of the remaining
> image.
>  Note that Polysulfide toners work on silver images
> directly and do not need a bleach step Thiocarbamide works
> as a "redeveloper" where the image has first been bleached.
>  Polysulfide toners can be made to have low odor by
> keeping the pH fairly low. The IPI toner contains Borax
> rather than carbonate as does KBT. I have never seen a MSDS
> for Viradon. The only ingredient shown on the label is liver
> of sulfur. Liver of sulfur dissolved in water will work
> without an added alkali.
> 
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@xxxxxxxxxxxxx
> 
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-- 
Regards Chris Woodhouse


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