[pure-silver] Re: Old paper and Defender 58-D

A bit more on chlorhydroquinone: a formula  and discussion:

http://www.apug.org/forums/forum222/33800-edwal-111-a.html

And another snippet of info:

"...I defer to Mees, Tull, Neblette, Hauff, Bogisch, Lumiere, Andresen, Haist 
and researchers of similar reputation whose reports were both authoritative and 
accurate, and did not - to the best of my current knowledge - mention anything 
about hydroquinone image stain. ..." My emphasis.

Before I quote something else, I'd just like to say two things:

-I'd trust the guys here who say that hydroquinone forms a stain image even if 
I didn't already know it, and

-few of the standard texts (or at least those I have) go into much detail on 
stain images, if they mention it at all, but they do cover tanning. Tanning and 
staining may not be the same, but they are similar, and if the developer 
oxidation product is coloured then there is likely to be a link between tanning 
and the formation of a stain image.

OK, so on to L P Clerc's Photography Theory and Practice, 1971 edition revised 
by R. E. Jacobson, Vol 4, Monochrome Processing:

"573. Oxidation Products of Developers; Tanning; Secondary Images.
The quinonoid oxidation products of developers that are formed in the absence 
of sulphite, or in the presence of very low concentration of sulphite, are 
deposited in the gelatine at the site of development, and in a quantity 
proportional to the amount of silver halide reduced. Usually they polymerize, 
giving rise to coloured, tanning substances of the nature of humic acids, whose 
exact constitution is unknown.

After removing the silver image ... a yellow or brown secondary image remains, 
which, though it may not appear very intense to the eye, can give acceptable 
prints on high contrast paper because of its absorbtion of actinic light. The 
following table (Lumière and Seyewetz, 1928) shows the colour of the secondary 
image obtained in various developers, its relative intensity and the 
concentration of sulphite necessary to prevent its formation.

Developer -- colour -- relative intensity -- sulphite g/litre

Pyro -- yellow-orange -- 10 -- 11
Catechol -- black -- 10 -- 6
Hydroquinone -- yellow-brown -- 10 -- 2
Chlorhydroquinone -- yellow-brown -- 10 -- 2
Amidol -- reddish-brown -- 8 -- 2
p-Aminophenol -- brownish-black -- 3 -- 2
Metol -- brownish-black -- 2 -- 1
PPD -- Grey -- 1 -- 0
Glycin -- None."


Best,
Helen
.................................................

On anti-fog: there is a stronger compuond than benzotriazole: it's called 
phenyl-mercapto-tetrazole

From a private converstaion with Ron Mowry (Photo engineer:)

Cor;

Sorry, my answers have not been up to par. I've had a bad 2 weeks with flu.

The total starting concentration in the developer is 1 mg / liter for a usual 
case of fog. You can go up or down from there. It is added from an alcohol 
solution of about 1% or whatever is comfortable. I've used 0.1% and 10% 
solutions. It really makes no difference. At 1% (1 gram / 99 grams of alcohol), 
then 1 mg would be hard to measure out. At 0.1% or 100 mg / 100 grams of 
alcohol, it would be easier to measure out.

It is an odorless white powder.

The only photo supplier that has any that I know of is the Photographers 
Formulary, but they have not listed it in their catalog as they only got it 
recently.

It is a very powerful antifoggant, one of the strongest there is.

Ron Mowrey


Best,

Cor

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