To Photo Engineer

kevin klein · 03-03-2007, 05:30 PM

Dear sir

Last night I made a batch of unwashed emulsion and shot a number of plates today, It worked out better than I expected with better contrast, density and speed compaired to what I have been using. The main thing is that the emulsion after development exhibits a surface texture similar to that of hypo chrystals as when fixer is left out and dried in the tray,as small small linear surface lines, but does not seem to cause any problems other wise other than a tendancy to lift from the plate some times.

The stuff is thicker than the other emulsion I have been using and coats better, sort of like a double cadmium collodion. Would less gelatin or more water result in a smooth consistent surface with out sacrificing the image quality?

Inert gelatin was used with sensitiser, accidentaly used twice as much as shuld have been used. Could a new batch be made and intermixed with this one, or should it be washed? What effect will washing have?

Also,is the addition of potasium bromide as a final for stabeliser a good idea for this emulsion?

I do'nt mean to sound whiney but this is one of those things where simpler might be better.

Thanks
KPK

Photo Engineer · 03-03-2007, 05:37 PM

The effect you describe is typical of unhardened emulsion or hardened emulsion that is not left to dry long enough. What you describe is severe reticulation.

It could also be due to the lack of adhesion to the support. This would be the case of an unwashed emulsion on glass or film, or emulsion coated on a poorly subbed film.

As a final stabilzer to a washed emulsion, potassium bromide is a good stabilizer, but the Tetra Aza Indene I describe elsewhere, and which is in Jim Browning's article is even better. I'm trying to arrange to have it made available as a solution from a distributor as it is tricky to make up.

The final coated gelatin should be between 5 and 12% with the best being around 8 - 10%.

You cannot easily mix a sulfur sensitized emulsion with one that is unsensitzed, but you can mix a spectrally sensitized emulsion with one that is not spectrally sensitzed and sometimes get good results.

Adding too much sulfur increases fog, adding too much sensitizing dye will decrease speed and contrast.

Emulsion making is not easy, but once you learn it, it becomes easier and easier with each repeat performance.

All the best to you.

PE

Neanderman · 03-03-2007, 06:04 PM

Could you please give this some context? Percentage of what?

Quote:

Originally Posted by Photo Engineer

The final coated gelatin should be between 5 and 12% with the best being around 8 - 10%.

PE

Ed

Photo Engineer · 03-03-2007, 07:04 PM

Gelatin in water. That is, for 10%, 10 grams of gelatin in 100 grams of total emulsion. The gelatin is 250 BI photo grade, bone gelatin.

Pe

kevin klein · 03-04-2007, 06:08 PM

Thanks for the info. I did wash the emulsion and it is behaving much better.
The speed and density are much better than what I have been using.

As far as I am concerned this simpler bromide emulsion is the thing to use, I am very pleased, good density for albumen printing.

Photo Engineer · 03-04-2007, 06:14 PM

You said it was one I posted earlier.

Was this the Ammonia emulsion?

PE