Re: Increasing Carbon speed.

It is in credible that incredible.
> > (but just under the roof...)
>
> Not really. I get that much increase in speed in
> chlorobromide emulsions with a different dopant.

It depends on the initial emulsion whether it is
incredible or not. I doubt you would get that much
increase with every emulsion.

> > You did not report your starting speed.
>
> If you are just looking at the magnitude of speed
> increase, that is irrelevant.

I disagree. There are limits.

I've seen the effects in both slow and
> fast emulsions.

Very slow and pretty slow, sure, but probably not if you
are starting with a High Speed negative emulsion, That
might indeed be incredible.

> These are in conjunction with chemical
> sensitisation,

Do you mean sulfur sensitisation?

I doubt that you would get 2 stops increase over
sulfur+gold sensitisation.

Anyway, it is almost meaningless to describe results
between emulsions of differing crystal size and habit.

Still, if those are your results then good.

I don't have any burning desire to try and duplicate your
work. But if you have to talk about your experiments it
would be nice to know what paper and which dopants you are
referring to.

> What happens when it doesn't work?
You'll get no speed increase or some loss.
>[Everything else being] the same. Only presence of
> dopants is modified.

Well, there must be some inconsistency in your
procedure... when things really are the same, it should be
as predictable as clockwork.

>With chloride emulsion the other
>dopant seems to increase contrast, so I have
>*unwashed*chloride paper made with single
>jet that is just as fast and contrasty as commercial
>papers.

Which commercial papers?

Contact or Enlarging?
Chloride ("AZO") Chlorobrobide, or Bromide?
Even chlorobromide emulsions can range from very slow to
very fast... more than 8 stops range...

I am not sure you have to resort to using such unusual or
left-field methods to attain suitable results.

> > Why on earth was your attention drawn to cerium?
>
> Because it's on the earth, and it's described in
> literature.

Well, that explains everything!

There is a lot of literature on Cerium salts in
photothermography, and I have seen some work on cerium in
color developer formulations as well... but I personally
have not read any specifically dealing with cerium and
ordinary chlorobromide emulsions. But then again, there
are hundreds of thousands of papers and I have not seen
them all!

More important to me is to understand what you are trying
to accomplish.

So far all I can figure out is that you wanted to make a
simple unwashed chloride emulsion, probably a high speed
version, with adequate contrast. You found your contrast
was too low so you looked into the use of use of dopants

Is this about right?

>
Iodide content seems to affect the effect of doping as
well...

Yes I would be very surprised if it did not.

I only tried a couple of points so don't know much.
Please let us know how it goes....

> Now you have to describe your emulsions.

Send me your address and next time I make a batch I will
send you a sample!

:+)

Ray

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Received on Thu Dec 16 05:52:40 2004