[alt-photo] Re: tintype developer formula?

[Richard Knoppow]

----- Original Message ----- 
From: "Christina Anderson" <zphoto at montana.net>
To: "The alternative photographic processes mailing list" 
<alt-photo-process-list at lists.altphotolist.org>
Sent: Monday, January 02, 2012 6:17 AM
Subject: [alt-photo] Re: tintype developer formula?


Cor,
I can answer that one: a tintype developer for liquid 
emulsion needs to essentially fog the gelatin silver layer 
so it is brownish/yellowish and shows up on the black plate. 
Thus the addition of fixer to the developer. It still 
requires fixing.

I figured out a recipe that would use dektol, sodium 
sulfate, and ammonium thiocyanate but am not quite sure 
whether the proportions have to be within an exact gram 
amount or not.
Chris

Christina Z. Anderson
christinaZanderson.com

On Jan 2, 2012, at 9:09 AM, <C.Breukel at lumc.nl> 
<C.Breukel at lumc.nl> wrote:

> Interesting, Christina
>
>
> The formula almost looks like a Monobath developer, 
> itcontains jut one developing agent as well as a moderate 
> amount of hypo (fixer), I guess not sufficient for proper 
> fixing, but might have an effect on the silver atoms 
> shape..Richard chime in please..;-)..
>
> Best,
>
> Cor

    I'm no expert on this but a couple of things occur to 
me: the silver image can be reflective when the grain if 
fine enough. This effect can be seen on very fine grain 
negatives where a positive image can be seen by reflective 
light, especially if the image is not very dense. This does 
not come from fogging but rather is a property of the very 
fine grains.
    Grant Haist wrote a small book on monobath processing, I 
don't remember the exact title. It may be available via a 
book search. He also discusses monobath processing in his 
large book on photographic chemistry. Monobath must not be 
confused with reversal processing, they do different things. 
Monobath produces conventional negatives, the idea is that 
the developer and fixing agent are contained in the same 
bath. Because both begin to work as soon as they soak into 
the emulsion the developing agent must be one that is 
energetic so that the required amount of development takes 
place before the fixing agent destroys the latent image and 
dissolves the halide. Haist makes a good case that monobath 
development works better for some materials than 
conventional processing resulting in finer grain and good 
tone rendition. The formula must be adjusted for the 
particular negative material its to be used with. A properly 
compounded monobath does not result in any speed loss 
compared to conventional development. However, the bath is 
often very alkaline so the emulsion must be hardened or the 
bath must contain an organic hardener capable of functioning 
in the high pH environment.
    Monobaths can also be used for print development, I 
think Haist discusses this a bit.
    Tintypes, while they are direct positives are _not_ a 
reversal process; the image is a conventional negative image 
but is viewed by light reflected _by the image_. This is in 
contradistinction to a conventional print. In a normal 
print, or most alternative processes prints, like Platinum 
or carbon, the light is reflected by the support, not the 
image. The image serves to modulate the amount of light 
transmitted to and reflected from the support. The image on 
a tintype must be such as to be reflective. It is likely 
that the use of hypo or thiocyanate in tintype developers is 
to aid in obtaining the requisite fine grain. Both are fine 
grain agents found in conventional fine grain developers, 
for example sodium thiocyanate is found in Kodak DK-20.
     A problem with some very fine grain negative 
developers, which might also be a problem for tintypes, is 
the production of dichroic fog: the fine grain agents are 
solvents for the silver halide and tend to release a certain 
amount of halide which is deposited on the surface of the 
film and converted to metallic silver by the developer. This 
coating is of extremely fine silver, the kind sometimes 
called colloidal silver, and is reflective in one color and 
transmits in another color, hence the name "dichroic fog". 
This would, of course, veil the shadows of a tintype 
reducing its contrast. In some extra-fine-grain developers a 
silver sequestering agent is used to insure that the silver 
dissolved by the halide solvents remains in solution and is 
not deposited on the emulsion.
     Fogging is required for _reversal_ development. In 
practical reversal development its produced either by adding 
a fogging agent to the reversal bath or by flashing with 
light. Hypo or thiocyanate, or other halide solvents, are 
added to reversal first developers to avoid veiling of 
highlights by silver halide crystals which remain in the 
emulsion after the first development but are so insensitive 
that the original exposure does not make them developable. 
If they remain in the emulsion they do become developable 
after the fogging step and result in veiling of the 
highlights of the reversed image and an effective 
substantial loss of speed.
     As with monobath processing a reversal process must be 
tailored to the particular material being developed.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk at ix.netcom.com