Re: Trick for increasing speed of photo papers?

----- Original Message -----
From: "Bill William" <iodideshi@yahoo.co.jp>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Thursday, November 18, 2004 1:21 AM
Subject: Re: Trick for increasing speed of photo papers?

> ---
> From: Liam Lawless
>> I haven't tested "speed increasing" ideas, but...
>
>> I'm afraid to tell you but this is not going to
>> work... Pretty much all practical developing agents
> give pretty comparable speed when used at the optimal
> condition...
> ----
> Don't be discouraged by Ryuji's comments. You should try
> it for yourself. You never know what you will discover.
> The developer you are using may not be optimized, and you
> may not notice or care if the there are other changes in
> the emulsion.
>
> There certanily are ways emulsions can be speeded up... it
> is done all the time.
>
> While it is true that a good emulsion is already at or
> near it's best speed, and trying to get more out if it may
> be more trouble than it is worth, it can be done.
>
> I don't know the material you are using but some areas for
> you to consider are:
>
> 1. Washing prior to exposure
> 2. Color sensitization
> 3. Increasing the pH of the emulsion or the developer or
> both...
> 4. Hypersensitzation
> 5. Gold Latensification
> 6. ???
>
> As everyone knows, emulsions increase in speed up to a
> certain peak then the speed starts to fall... at that
> point, they begin to fog more or less rapidly...
>
> You may be able to get some speed just by waiting, or by
> accellerated aging of your material...
>
> I guess you don't have the time or will to go that route,
> but the point is yes it can be done...
>
> But 2 or 3 stops?
>
> That is quite a bit!
>
> But even so, it is a possibility, as new sensitization
> technology has been developed
> which does this exact thing.
>
> Some of the things that can be done may not necessarily be
> speed increasing per se, but for all pratical uses may be
> similiar in that they allow you to get the picture made.
>
> There are many possible roads to travel.
>
> You may not find the Stairway to Heaven, but I hope you
> have a nice trip!
>
> Ray
>
> (Everything said, adding another Ray of Light might be the
> simplest... but Panalure does have a very high speed
> emulsion, and there are others too in the same speed
> range.)
>
   A couple of things need pointing out. First paper
emulsions differ from film emulsions. Also, paper emulsions
are developed to their maximum contrast which film emulsions
are not. "Pushing" film is actually just increasing the
contrast by increasing development. This is not an option
for paper because the development is already carried out
about as far as it will go.
   Most of the sensitivity increasing methods used for film
are actually ways of decreasing reciprosity failure for very
long exposures as are typical in astrophotography. They do
not reallyl increase the overall sensitivity of the film.
   I don't know what you mean by new ways of increasing
sensitivity. Perhaps Ryuji knows of some, but at as far as I
know the techniques are about the same as they have been for
decades.
   Again, film and paper emulsions are different and are
made differently. For one thing the amount of ripening is
different. Ripening is a sort of slow cooking of the
emulsion mixture during which the nature of the crystals
changes. Much of the increase in sensitivity comes from the
exact way the ripening is done. Other sensitizers include
sulfide, which is perhaps the most important, whether
ammonia is used in the emulsion, metallic sensitizers like
Gold and Cadmium and other subsances. Some of these are
added toward the end of the process but some must be used
early because they affect the way the halide crystals grow.
Since Ryuji has been studying and making emulsions I would
pay attention to his opinion about this.
   Some substances may increase sensitivity but will also
increase fog a lot which is intollerable in prints.
  I tend to agree with those who suggest getting more light
through the negative. In order to help with this it would be
useful to know what sort of enlarger and enlarging lens is
being used and of course the format of the film and size
desired size of the prints.

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