Making your own film

[Photo Engineer]

I don't know of any formula that used Cobalt salts. That is not to say there are none, but no Kodak formula I knew of did, nor did any from other manufacturers that I have studied.

PE

[Photo Engineer]

Thinking this over more, I would suggest that the citations listed in our patents on cobalt incorporation into coatings would be a good place to start a literature search. Our work on cobalt incorporation involved a lot of work on prior art. Maybe this would help.

My co-workers and I probably did more work on cobalt in coatings than anyone else. IDK for sure but the patent searches were rather complete and the citations were definitive in this area IIRC.

PE

[rmazzullo]

Hello PE,

I know there have been previous discussions about the differences between active and inert gelatin. Have there been any discussions about the Bloom rating of gelatin, and its effect on emulsion making?

How does the "Bloom" rating of gelatin change an emulsion formula? Are there other changes that should be taken into consideration (changes in viscosity), or -- properties that can be taken advantage of -- by using gelatins with different Bloom numbers?

Thank you,

Bob M.

[Photo Engineer]

Bob;

Bloom rating gives an indication of viscosity and ability to peptize (or surround) the silver halide crysta. It has nothing to do with the 'bloom' in German literature on photography related to ripening of emulsions.

We did not use it at EK as it is meaningless when doing coatings with a slide hopper, and it is also meaningless when doing ISO washes with PA gelatin. We used special gelatins for precipitation.

Usually we favored high BI gelatins of about 250 - 275.

PE