Silver Halide Sizes

[omaniengr]

Hello all,

I am a newbie in the emulsion making world and looking forward to learn this. I am working on a project to replace gelatin with another materail (cannot disclose this for now). What I want to know two things:

1- how to control and measure the silver halides sizes once suspended in the emulsion.
2- how to make the silver halides chemically developable?

My first version of the emulsion used potassium chloride and silver nitrate and the new gelatin-like materail. With this version, I was able to expose images under UV light on the emulsion. The image appear immediately in the new emulsion (not latent). I was not able to develop it chemically using microfilm developer (image gets destroyed). I ordered additional materail like potassium bromide and iodide for further experimenting and a copy of the Light Farm book

Thanks

 

[Photo Engineer]

You may want a copy of my book as well then. It goes into questions such as yours and my second book will do more (I hope).

Basically, all silver halide is UV sensitive and once exposed can be chemically developed. If you over-expose and then develop, the image is destroyed.

Remember that an average proper exposure for developing out is not visible until you immerse it in developer, and if it is, you have badly overexposed it.

After you run Silver Nitrate into the salt + peptizing agent, heat treatment at 50 - 80 deg C causes grain growth as long as there is nothing in the solution that can cause odd reactions to occur. This process can be sped up or slowed down by time, temperature and addition of silver halide solvents such as Ammonia. It can be retarded by restrainers such as TAI and PMT. These are both available from the Photographers Formulary.

PE

 

[omaniengr]

Thanks PE for the information. Other than electron microscopy, do you know if a way to measure the silver halide sizes? From the literature review I did, the initial silver halides would be less than a micron in size and can be grown as you explained. My goal is to produce halides that are less than a micron.

Also, what is your book name? I thought Light Farm book belongs to you.

 

[Photo Engineer]

My book is advertized here on APUG and is sold by the Formulary in Montana. It gives a bit more scientific information.

I use EM testing, but Nephelometry might help. Even so the results would only be approximate. When you change out the gelatin for another peptizing agent, all bets are off though on getting any rough measure of size. Speed is one approximate way, if you test before any chemical sensitization with sulfur or gold.

It is not necessarily true that grain sizes are under 1 micron in size. Depending on conditions, you can get from very small, or about 0.1 microns or less, up to 10 microns.

The book is "Emulsion Coating and Testing" and comes with an optional set of DVDs.

PE

 

[MattKing]

Also, what is your book name? I thought Light Farm book belongs to you.

The Light Farm book is Denise Ross'

 

[Photo Engineer]

Yes, she was one of my students at an early workshop at the Formulary.

PE