Re: physical developers

> My original curiosity was actually about the comparative
> speed of physical developing formulas...

Lumiere/Seyewetz (CR 1924) point out that physical development subsequent to
fixing used to require a 10x exposure time. However, they claim to have
substantially increased the speed of such a system.
They stress on the importance of pH control of the washing solution. Plain
water is said to destroy the latent image. So they advocate a slightly
alkaline washing solution.

Their developer was formed of:
A
sodium sulfite..........180g
silver nitrate............... 75g
water.....................1000ml

B
sodium sulfite.............20g
paraphenylendiamine 20g

150ml A + 30ml B

Lumiere/Seyewetz state that the grain size formed by physical developed did
not depend on the grain size of the initial emulsion.

> Anyone have any ideas for increasing the speed of physical
> development?

Use a more concentrated solution. Usually this increases grain size though.

> Does anyone know of any ultra fast acting physical
> developers ?

Yes, there was a Russian developer, introduced by Valery Petrov:

SP-4
sodium sulfite.................85 g
hydroquinone.................8,9 g
potassium hydroxide.....7,2 g
phenidone......................0,3 g
ammonium thiocyanate..22 g
water...................................1L

Development time is 5 - 10 seconds!

Martin

----- Original Message -----
From: "Bill William" <iodideshi@yahoo.co.jp>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, August 25, 2004 6:58 AM
Subject: Re: physical developers

> RK wrote:
> > Henry found that [grain] was no finer, and sometimes
> coarser, than D-76.
>
> to which MARTINM wrote：
> > For Lippmann emulsions physical developers may have
> > some advantages though.
> > They are able to produce grain sizes smaller than
> > 10nm...
>
> Yes, Martin, This is true!
> And I think 10 nm is smaller and thus finer...than
> whatever else was mentioned.
>
> Additionially, the time alloted to physical development is
> an important issue. I asked Richard for the ref. about the
> modern claim of no physical development occurring in
> ordinary processing... perhaps he was thinking about
> Richard Henry's book....
>
> But in general, considering the usual time required for
> physicall development, I never assumed that physicall
> development played a major role in production of image
> silver under ordinary circumstances... However under the
> correct circumstances, physicall development can be used
> to create extreamly small metal clusters... suitable in
> fact for holographic and very likely, lippmann images.
>
> While it may not play a major role in creation of image
> silver, that it doesn't occur is curious to me and I would
> like to hear more on the subject.
>
> My original curiosity was actually about the comparative
> speed of physical developing formulas...
>
> Anyone have any ideas for increasing the speed of physical
> development?
>
> (Martin has already mentioned gelatin hardness as one
> possible variable)
>
> Does anyone know of any ultra fast acting physical
> developers ?
>
> Ray
>
>
>
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>
Received on Wed Aug 25 00:43:07 2004