Re: Light sensitive compounds for alternative daguerreotypie

Ryuji,

Thanks for your response.

What I fail to understand is why things like platinum/palladium prints
and chrysotypes work. None of those three processes use silver unless
I'm missing something. If a piece of off-the-shelf B&W paper is just a
silver slurry smeared on paper and a piece of handmade platinum paper is
the same thing but substituting platinum for silver, what's the difference?

I'm frankly not sure what the gold chloride step does chemically but it
certainly makes the image on the dag plate more durable and enhances
contrast. If you're not careful and heat the solution too long on the
plate, solarization starts to occur in highlights. The whole gilding
process is unrelated to the photosensitive part of what's going on with
a daguerreotype though.

-Jonathan

Ryuji Suzuki wrote:
> I'm afraid that halogenating those metals won't make them
> photosensitive like silver halides, even if you could afford to use
> those metals. First of all, halides of those metals are generally
> soluble in water and you don't want that.
>
> Silver halides are not just some random combination. It has very
> useful property as a photosensitive material. Silver halides (except
> fluoride) are indirect bandgap semiconductor material (ask a solid
> state physicist, material scientist or an electrical engineer with
> semiconductor specialty for more details) and each grain of salted
> paper and gelatin emulsions work sort of like a photodiode, except
> that the response in AgX is roughly linear in log exposure, while
> semiconductor devices respond roughly linearly to linear exposure
> scale. (The latter is one of the difficulties in digital imaging
> systems.) People tried to replace silver with other material for
> various reasons (such as cost) but none was very successful.
>
> I don't know the details of how you treat your dag plates in gold
> chloride, but is there a specific reason to worry about the logevity
> of the treated material?
>
>
> From: Jonathan Danforth <jonathan@danforthsource.com>
> Subject: Light sensitive compounds for alternative daguerreotypie
> Date: Thu, 27 Jul 2006 12:59:09 -0400
>
>
>> All,
>>
>> I've been worrying a great deal lately about the longevity of
>> Daguerreotype on silver (despite the gold chloride gilding stage) so I
>> was wondering what people thought about working with other compounds.
>>
>> I know that you can use iron, gold, uranium, etc. salts to make images
>> but I'm wondering about the sensitization process. With Daguerreotypes,
>> I expose a silver plate to Iodine vapor and BAM... light sensitive
>> silver iodide. What I'm wondering is if I could do the same with 24kt
>> gold (a la the Chrysotype) or rhodium plate and make an image using the
>> same process using either UV or mercury as the developing agent.
>>
>> Ideas? Will it work using the same clearing and developing methods as
>> the Daguerreotype?
>>
>> -Jonathan
>>
>> --
>> http://photographs.danforthsource.com
>>
>>
>
>
>
>

-- 
http://photographs.danforthsource.com