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Hologram
09-13-2008, 07:43 AM
Hi,
Jeff uses difussion to intoduce the silver nitrate into the gelain coating. Unless I am way off, the only way to vary grain sise would be to coat a pre-existing, larger grain silver halide emulsion on the glass, then then spectraly sensitize the coating with dyes + ascorbic acid.
Do you have a source for the dyes Jeff used ?

I ment to say "spectraly sensitize by diffusion."


Yes, with the Diffusion method you can also spectrally sensitize a unsensitized AgX emulsion subsequently. In contrast to former bathing methods, this one uses a halide/dye/ascorbate solution for sensitization. I think it's this combination that does the spectral sensitization more efficiently than previous attempts.

As for forming larger grains with the Diffusion method, you could well do that by adapting the bath concentration. E.g. increasing the amount of halide most certainly does increase grain size. Similarly, longer bathing periods in the halide bath will equally favor the production of larger grains. Furthermore, you might increase the temperature of these baths and the drying section etc.

wildbillbugman
09-13-2008, 12:22 PM
Dear Hologram,
I wonder, why the lithium bromide and not potasium or ammonium bromide?
Bill

Hologram
09-14-2008, 03:02 AM
Dear Hologram,
I wonder, why the lithium bromide and not potasium or ammonium bromide?
Bill

According to Jeff Blyth lithium bromide does form smaller grains than potassium bromide (I am not sure about ammonium bromide). Furthermore, LiBr has better solubility in alcohols that may be important when using certain sensitizing dyes.

Photo Engineer
09-14-2008, 06:51 PM
Just a note for y'all.

Making an emulsion in-situ on a plate or film support yields a very slow emulsion due to the lack of proper solution emulsification steps. So, although it can be done, the results are slow emulsions.

Spectrally sensitizing them on plates has also been very difficult due to uniformity problems and other technical details. It can be done, but not with the efficiency that is achieved by doing it in the solution of pre-melt.

For those that have counter arguments, all I can say is that I have access to those who have done the above both ways. This was a summary of their comments.

PE

JOSarff
09-15-2008, 12:53 PM
Why is there a problem with purchasing sensitizing dyes? Is there some use that wI don't know about that makes them a 'banned' substance?

Joe

Photo Engineer
09-15-2008, 01:07 PM
Joe;

They are not banned. The good ones are very difficult to make with a limited market and therefore very expensive. They run about $100+ / gram. Thats about the whole story in a nutshell.

PE

wildbillbugman
09-15-2008, 07:51 PM
The larger companies,specificly Aldrich will sell some dyes
to anyone. But other specific dyes may be sold only to businesses and institution. Sometimes it is difficult to see the reasoning behind Aldriches classification of these dyes. I have not tried Fisher Scientific, but when I purchased some filter paper from them last week, the invoice had, in big bold letters "DO NOT SHIP CHEMICALS". I do not know if this is common, or if I am on the industral equivalent of a "NO FLY LIST". I am not an Arab, have never been in a Mosque, nor have I ever sent a nasty letter to a public official. In fact, I have had security clearances for some of my jobs. I think that it is "one Rule Fit All".
Bill

JOSarff
09-16-2008, 11:07 AM
I do not know if this is common, or if I am on the industral equivalent of a "NO FLY LIST". I am not an Arab, have never been in a Mosque, nor have I ever sent a nasty letter to a public official. In fact, I have had security clearances for some of my jobs. I think that it is "one Rule Fit All".
Bill

Nor am I, but it seems to get harder to get supplies every year. Just a venting.

Joe

Kirk Keyes
09-16-2008, 11:44 AM
Just don't ask about buying iodine or phosphorus - they'll mark you as a meth cook and you'll never be able to buy anything.

wildbillbugman
09-16-2008, 12:10 PM
Kirk,
Anyone who has bought crystaline Iodine from The Formulary has filled out a "DEA card". I don't know who gets these cards, but I have never been"Raided"(yet).
Bill

Neanderman
09-16-2008, 10:51 PM
'The Photographic Emulsion' by Carroll, Hubbard and Kretschman', Focal Press.

That book has been on my want list for a few years now. First time I think I've ever heard of an actual copy of it.

Ed

Kirk Keyes
09-17-2008, 10:32 AM
That book has been on my want list for a few years now. First time I think I've ever heard of an actual copy of it.

Ed

http://www.amazon.com/gp/offer-listing/B0016ST326/ref=dp_olp_2?ie=UTF8&qid=1221665512&sr=1-3

Neanderman
09-17-2008, 03:54 PM
http://www.amazon.com/gp/offer-listing/B0016ST326/ref=dp_olp_2?ie=UTF8&qid=1221665512&sr=1-3

Thanks!

Ed

Kirk Keyes
09-18-2008, 11:44 PM
Bill - how's it going? Did you get your analytical balance? My 3-place balance arrived today, I need to take the top off as it looks like the wieghts have gotten out of position during shipping.

Kirk

Photo Engineer
09-19-2008, 09:23 AM
Interesting Kirk.

I just got a "surplus" Kodak/Sartorius 10Kg 3 place scale for $100 at a scrap yard. It is in perfect condition and still has the Kodak ID tag. It is a monster with a top plate about 1 foot square and must weigh in at nearly 10 kg itself. It has a centering level on the top and I/O ports on the back so it can be computer driven. New, it must have cost a mint.

PE

wildbillbugman
09-19-2008, 12:05 PM
Hi Kirk,
Things came up, and I was not able to pick up the balance personaly. It was shiped to me yesterday. My sensitization dyes are still in the freezer. As soon as I get the balance and have made sure that it is properly calibrated, I will let the unoperned dyes come to ambient temperature befor I open them. Then I will weigh and ship to you and the other person who requested portions.
I have been working on a "special" project about which I am not ready to go public. But soon you will read about it in some form.
Cheers,
Bill

Kirk Keyes
09-20-2008, 12:16 AM
I just got a "surplus" Kodak/Sartorius 10Kg 3 place scale for $100 at a scrap yard.

Wow - that sounds nice. I bet that did cost a lot when new.

I pulled the top on my balance, and there was what looks like a box knife blade stuck to the magnetic dampener. But the mechanism is still out of alignment. Fortunately there is a shop in town that specializes on repairing analytical balances. I'll drop it off and see what they say. At least it was only $25.

Ahh, the joys of ebay...

wildbillbugman
09-22-2008, 04:21 PM
Hi all,
Ijust received my Answorth mechanical anylitical ballance. It looks clean and complete. Exept that some of the weights and other internal parts are "diconected". Fortunatly, the service who last calibrated it in 1983 is still in busines and only about 50 miles from here, in Burbank. I will take it in on Wednesday ,and hopefuly get it up and running.
Bill

Kirk Keyes
09-22-2008, 06:14 PM
Sounds good - I've decided to try again at another used balance - this time a 4-place. If it's going in for service, I might as well get something that is really worth fixing. SO there's another $40 into an analytical balance...

wildbillbugman
09-28-2008, 02:34 PM
[QUOTE=Photo Engineer;675608]For film, glyoxal or chrome alum or both in a mixture, but for plates only chrome alum is sugged.

Hi Ron,
Is your recomendation for the use of only chrome alum for glass plates only because chrome alum can act as an adhesion promoter for glass? If that is the case I do not think that it will matter. Because I follow A very strict preparation for my glass,I never,ever have frilling, hardened or not.
Could you offer a sugestion for concentration of chrome alum or glyoxal?
Regards,
Bill