[alt-photo] Re: metallic/chromo/gold/halochrome/Seigel/Dalla Tana

[Christina Anderson]

AHA, Alberto--that is why he still has whites.

He is what I term "selectively developing" by brush then--which would then keep parts of the print undeveloped/white.  I teach that in my class--students expose a print normally and develop normally but instead of immersion in the tray of developer they brush it on selective places to bring out the image, bit by bit, leaving the undeveloped parts white.

Those white parts, subject to the plating developer, would immediately turn silver, so Dalla Tana must be very careful to brush only the already developed parts again with the plating solution.  I did not realize he was brush developing.  If he is brush developing AND brush chromoing, it could keep paper white (what a pain).

When doing chromo, you can test the color by putting an unexposed piece of paper right in the chromo bath (my formula) and it will plate out beautifully.  So If Dalla Tana is keeping parts of the image white, he has to be only getting the plating solution on those parts of the image.  The minute that solution comes in contact with the whites it turns them silver.  BUT if he is using entirely different chemistry, all bets are off here and I don't have a clue.  OH, though, if you have a brush ready with stabilizer on it (in my formula) you can halt the silver creep.

OK, so for the second point--you are saying that Judy's formula is correct to plate out because it contains a reducer, but Halochrome must have something inert added in the 67.5% to allow this to happen (ascorbate, tartrate, aldehyde, glucose).  The Redeveloper part of the Halochrome is "Proprietary" so they don't list it, and don't have to I suppose, because it is inert.  Sneaky sneaky.  I will mix up a mock Halochrome and test sometime this summer.  I have tartaric acid and citric acid, would those be OK?

Thanks for the plating formulae, below. BTW, I found that if the temp is not warm, my chromo is slow to work.  One time I accidentally used hot water in the chromo bath (temp wasn't regulated in the individual lab) and boy did it work like crazy. This seems corroborated by your mention of 30-40 C in the plating formula.

Now I have a question for you:

In my chromo formula, why does Tektol work better than Dektol?  I list, again, the ingredients of all, but now including Dektol's ingredients as well.  Is it the absence of hydroquinone as one has suggested? Or is it the addition of sodium isoascorbic which is a good reducing agent? And, if that is so, couldn't one just add ascorbic acid to the Dektol?

Chris

Activator (pH 14)
Weight %/ Chemical Name
5-10        potassium hydroxide
5-10        sodium sulfite      

Stabilizer (pH 4.85)
Weight%/ Chemical Name
15-20        ammonium thiocyanate
5-10        sodium metabisulfite 
1-5               acetic acid
(works best with Tektol, not Dektol, so see below for ingredient comparison)

Tektol (pH 10.35)
Weight%/Chemical Name
10-25                         potassium carbonate
7-10                         sodium sulfite
5-10                         sodium isoascorbic
1-5                         triethanolamine           

Kodak Dektol, for comparison (pH 10.2-10.4):
Weight%/ Chemical Name
50 – 55       sodium carbonate, monohydrate
30 - 35        sodium sulfite
5 - 10        hydroquinone
1 - 5        bis(4-hydroxy-N-methylanilinium) sulfate
1 - 5        potassium bromide
_________________________________________

On May 2, 2010, at 12:51 AM, Alberto Novo wrote:

> Christina,
> thanks for sharing your research.
> Only a few remarks: 
>> I am most positive Dalla Tana is doing it on a developed and fixed/previously made print as you can see, below, in the Halochrome section.
> 
> Dalla Tana writes (both in the Italian and English texts) that he develops by brush for 10-15' (Why by brush? Perhaps because he don't want to use too much developer? Because he wants that the developer is completely exhausted at the end? Because he don't want to smudge the back of the paper?...), then he plate (or tone) before stopping and fixing. 
>> "Redeveloper Formula:
>> Halo-Chrome® Silver Toner (1)
>> AMMONIUM HYDROXIDE (SARA III) Percent: 30
>> SODIUM HYDROXIDE (SARA III) Percent: 2.5
>> NON-HAZARDOUS INGREDIENTS AND WATER Percent: 67.5 POST FACTORY  © JUDY SEIGEL
>> STEP TWO:  REDEVELOPER FORMULAE STOCK SOLUTIONS (mix 1 +10 at time of use)
>> 2 g. hydrazine sulfate
>> 1g hydroxylamine hydrochloride
>> 50ml 25% ammonia
>> 120ml 10% sodium hydroxide
>> 40-200ml distilled water.
>> (and LOTS of other formulae).
> 
> Without a reducing substance (hydrazine and hydroxylamine in P.F. formula) there will be no plating out. So, among the "non-hazardous ingredients and water" there has to be the reducer. Because hydrazine and hydroxylamine are hazardous, I could think to something like ascorbate, tartrate, an aldehyde or glucose.
> The formula for silver plating a glass is very similar:
> 1) solution of silver nitrate and ammonia
> 2) solution of silver nitrate and Rochelle salt
> Mix the solutions and pour over the glass. Wait about 30' @ 30-40°C
> or (from the Tollen's test for aldehydes):
> 1) solution of silver nitrate, sodium hydroxide and ammonia
> 2) solution of glucose or sucrose+acid (this last can be used only some days after the preparation)
> mix, etc. Plating is immediate.
> WARNING!!! throw the mixed solution and rinse the vessel ASAP because the silver + ammonia solution with time forms silver azide, which detones simply by rubbing also if it is wet. 
> 
> Alberto
> www.grupponamias.com
> www.alternativephotography.com/articles/art102.html
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