Re: Dry Plate Speed & Shelflife

> I disagree with pretty much all that's said above.

 In my "above" statement I was referring to that particular method, also
known as "Diffusion method" or "Bathing method". I didn't mean to say that
method represented the holy grail in silver halide emulsion making. However,
I think it's at least an interesting and easy way to achieve silver halide
"quickies" or to experiment with certain new emulsion ingredients.
Frankly, I don't understand the nature of your disagreement. Note there are
some people around to have successfully tested that method - actually, there
even exists a commercial product according to that method.

> Reduction sensitization is effective but unless it is combined with an
> effective way to control its reaction kinetics as well as
> after-reaction stabilization, this technique is bound to fog. This is
> a very tricky issue you can find in literature from 50s and 60s when
> people at Kodak and Fuji were trying hard to make good use of
> gold-sulfur(or selenium)-reduction sensitization with acceptable level
> of fog.

Being not particularly familiar with that literature, I nevertheless can
assure you that the method described at
http://cabd0.tripod.com/holograms/id3.html does not yield fogged plates and,
believe me, in the area I am interested in, fog matters a lot.

> I don't know how you can incorporate ripening into that process
> without undermining other photographic properties of the sensitized
> plate. You may be able to increase the crystal size by adding a
> thioether, thiocyanate or ammonium salts, but then unless you remove
> them soon after crystalization, problems will most likely arise.

I don't see any particular difficulties with that.
It may be interesting to point to Glafkidès, Chimie et physique
photographiques, Paris 1967 (unfortunately, I don't have the English
translation). He writes (p.329/330):
"On peut enfin réaliser des surfaces sensibles au trempé à l'aide de films
préalablement gélatinés ou d'anciens film débromurés. L'auteur a mis au
point, il y a longtemps, un mode opératoire qui consiste a immerger, pendant
une minute un film débromuré, lavé, rincé à l'eau distillée et essoré, dans
une solution de nitrate d'argent à 10% pendant 1 à 2 mn (1 mn si le film est
sec). Le film imbibé de nitrate est essoré et immergé pendant 30 s
exactement dans une solution contenant 25% de bromure de potassium et 5% de
bisulfite liquide. Rincer ensuite 30 s, essuyer mécaniquement ou au jet
d'air, et laver 2 mn. Placer le film sensibilisé dans une solution de
ferricyanure de potassium à 1g/l, pendant 2 à 3 mn. Laver 2 mn. On peut
augmenter la sensibilité par 4 en traitant de plus, par une solution de
colorant sensibilisateur à 16 mg/l et 25% d'alcool. Rincer finalement
pendant 30 s, essorer et sécher.

La durée d'immersion dans le bromure de potassium et la température de la
solution sont critiques pour une bonne reproductibilité des résultats. Si la
durée dépasse 30 s, le grain grossit et le contraste s'abaisse. Inversement
si l'immersion et plus courte, le contraste est accru. On peut encore
l'augmenter par addition, au bromure, de 50 ml/l de chlorure double de
rhodium et d'ammonium à 1g/l; l'addition d'iodure de potassium abaisse la
rapidité, celle de chlorure agit de même, sans changement de contraste, mais
dans ce dernier cas le ton est plus chaud."

> In conventional emulsion making system, it's easy to reduce grain
> size. But it's also easy to increase grain size. I never aim smaller
> than about 50nm (not that I measure the grain size-frequency
> distribution or anything) or greater than just below a micron, smaller
> grains are easier to make with high contrast and also take less time.
> Amino acid composition of the gelatin (methionine and cysteine for
> example) has influence on this, as well as dopants and addenda that
> adsorb on AgX crystals to retard ripening. You can add a very small
> amount of cysteine for this purpose. PVA is also known to retard
> ripening greatly. You can also precipitate at a low temperature. After
> all, in a simple single jet system, it's often that all you need to
> decrease avg grain size is to dilute the salt in the kettle (keep the
> salt constant but put more water and adjust gelatin). In order to make
> crystals bigger, you'll need a ripener, or maybe combination of
> multiple ripeners, like a thioether compound (which is always on) and
> ammonium sulfate (which can be turned on or off). You'll have to spend
> longer time to grow crystals, because if you try to grow them too
> fast, renucleation will occur and you'll have too many dead grains.

For the making of ultra-fine SH emulsions the challenge consists in forming
very small grains and keeping them small. In addition, dealing with very low
light
levels, speed has to be pushed to the maximum. This is not a trivial task.
In theory it may look easy to apply the techniques you mentioned (special
grain growth inhibitors might be an other option), to actually make such
emulsions may be a different ball game though.

> High intensity is difficult to use because of high intensity
> reciprocity failure. This is the major problem with chemically
> developed color papers used for high quality digital output, where
> paper is exposed by LED or other light source. In order to expedite
> the exposure, the light output must be increased, but HIRF becomes the
> problem. This is particularly problematic because color papers are
> mostly silver chloride to make the development and fixing process very
> fast. AgCl has very poor HIRF characteristics. So manufacturers use
> all sorts of techniques such as core-shell profiling, multiple doping,
> etc. to improve HIRF characteristics.

I have at least one paper that indicates a connection between HIRF and
reduction sensitization...

> You say a few milliwatts but that's still a lot compared to exposure
> from an ordinary enlarger or especially in camera exposure.

Probably not. It has been a couple of years since the last time I used an
enlarger, but I believe to have had access to a 150 W (= 150 000 mW) light
bulb then. Optical losses run high in both cases. Even considering the large
bandwidth
(and the large part wasted in form of heat) of an enlarger's light
source, I still have to get along with my few milliwatts (per cm/2) only...

> Double jet system is certainly useful for greater control, but it is
> not really a strict requirement for useful emulsions in the sense of
> classical photography. Emulsions like Panatomic-X, Agfa Isopan, Ansco
> Superpan Supreme, etc. are presumably all made by single jet
> process. So are almost all AGFA emulsions from WW2 era. I can even use
> a disposable plastic pipette as a jet to make an emulsion like
> those. For that matter, even some rudimentary tabular grain emulsions
> can be made with single jet setup if the precipitation conditions are
> set just right.

Yes, I've done that a lot.

> I've done it. Stannous chloride, ascorbate, sulfite, and a couple
> other organic agents. However, I'm pretty happy with S+Au
> sensitization without deliberate reduction sensitization.

OK, I didn't mean to sell you reduction sensitization. Speaking of SH
emulsion making, I just wanted to point to the possibility of reaching the
same goal by different means.

Martin

----- Original Message -----
From: "Ryuji Suzuki" <rs@AgX.st>
To: <alt-photo-process-l@sask.usask.ca>; <martinm@SoftHome.net>
Sent: Thursday, March 03, 2005 10:21 AM
Subject: Re: Dry Plate Speed & Shelflife

> From: MARTINM <martinm@SoftHome.net>
> Subject: Re: Dry Plate Speed & Shelflife
> Date: Thu, 03 Mar 2005 09:08:40 +0100
>
> > Besides the ascorbate sensitization, one of its advantages stems
> > from the high amount of silver halide present in the
> > emulsion. Regarding ripening (and possibly gold sensitization), I
> > guess this could be easily integrated into the schedule of this
> > method. As you know, it's always much easier to inrease grain size
> > than to achieve the opposite.
>
> I disagree with pretty much all that's said above.
>
> Reduction sensitization is effective but unless it is combined with an
> effective way to control its reaction kinetics as well as
> after-reaction stabilization, this technique is bound to fog. This is
> a very tricky issue you can find in literature from 50s and 60s when
> people at Kodak and Fuji were trying hard to make good use of
> gold-sulfur(or selenium)-reduction sensitization with acceptable level
> of fog.
>
> In my experience, fog due to overdigestion with sulfur comes rather
> gradually, but fog from excessive reduction sensitization comes more
> rapidly. (These days people fight for speed with tellurium
> sensitization, and of course fog is the problem.)
>
> I don't know how you can incorporate ripening into that process
> without undermining other photographic properties of the sensitized
> plate. You may be able to increase the crystal size by adding a
> thioether, thiocyanate or ammonium salts, but then unless you remove
> them soon after crystalization, problems will most likely arise.
>
> In conventional emulsion making system, it's easy to reduce grain
> size. But it's also easy to increase grain size. I never aim smaller
> than about 50nm (not that I measure the grain size-frequency
> distribution or anything) or greater than just below a micron, smaller
> grains are easier to make with high contrast and also take less time.
> Amino acid composition of the gelatin (methionine and cysteine for
> example) has influence on this, as well as dopants and addenda that
> adsorb on AgX crystals to retard ripening. You can add a very small
> amount of cysteine for this purpose. PVA is also known to retard
> ripening greatly. You can also precipitate at a low temperature. After
> all, in a simple single jet system, it's often that all you need to
> decrease avg grain size is to dilute the salt in the kettle (keep the
> salt constant but put more water and adjust gelatin). In order to make
> crystals bigger, you'll need a ripener, or maybe combination of
> multiple ripeners, like a thioether compound (which is always on) and
> ammonium sulfate (which can be turned on or off). You'll have to spend
> longer time to grow crystals, because if you try to grow them too
> fast, renucleation will occur and you'll have too many dead grains.
>
> > Well, you might be surprised to learn that the power levels involved
> > with those lasers - most of the time - are extremely low. Whereas
> > youre likely to handle several kilowatts of light power, we're
> > usually dealing with a few milliwatts only.
>
> High intensity is difficult to use because of high intensity
> reciprocity failure. This is the major problem with chemically
> developed color papers used for high quality digital output, where
> paper is exposed by LED or other light source. In order to expedite
> the exposure, the light output must be increased, but HIRF becomes the
> problem. This is particularly problematic because color papers are
> mostly silver chloride to make the development and fixing process very
> fast. AgCl has very poor HIRF characteristics. So manufacturers use
> all sorts of techniques such as core-shell profiling, multiple doping,
> etc. to improve HIRF characteristics.
>
> You say a few milliwatts but that's still a lot compared to exposure
> from an ordinary enlarger or especially in camera exposure.
>
> > I guess it depends on the scale of emulsions to be produced. For
> > small experimental batches the bathing methods might remain
> > attractive: no need for double-jets - though I have to admit
> > reproducibility might be an issue.
>
> I don't think so. Conventional emulsion is not that hard to make from
> 50ml up to a liter. If you are coating on glass, not paper, half of
> the problem is solved as well.
>
> Double jet system is certainly useful for greater control, but it is
> not really a strict requirement for useful emulsions in the sense of
> classical photography. Emulsions like Panatomic-X, Agfa Isopan, Ansco
> Superpan Supreme, etc. are presumably all made by single jet
> process. So are almost all AGFA emulsions from WW2 era. I can even use
> a disposable plastic pipette as a jet to make an emulsion like
> those. For that matter, even some rudimentary tabular grain emulsions
> can be made with single jet setup if the precipitation conditions are
> set just right.
>
> pAg controlled, computer profiled precipitation system is something I
> don't have. But I've made quite a few double jet emulsions using giant
> disposable medical syringes, or simply two burettes hung over the
> kettle. It's not that hard.
>
> > Anyway, you might at least give the ascorbate reduction
> > sensitization a try...
>
> I've done it. Stannous chloride, ascorbate, sulfite, and a couple
> other organic agents. However, I'm pretty happy with S+Au
> sensitization without deliberate reduction sensitization.
>
> --
> Ryuji Suzuki
> "Well, believing is all right, just don't let the wrong people know
> what it's all about." (Bob Dylan, Need a Woman, 1982)
Received on Fri Mar 4 02:18:32 2005