Black and White Films With Two Emulsions

There may be some confusion because of how the photographic industry uses the word "emulsion". I'll suggest a few definitions that are consistent with one another:

1. Film type like "KODAK TRI-X Pan/ 5063". i. e. "Tri-X is my favorite emulsion."
2. A specific box or case of film, "KODAK TRI-X Pan/ 5063, 0251". i.e. "I try to use the same emulsion for the entire shoot".
3. In manufacturing an emulsion layer my be very different (speed/ grain size, color couplers) from other layers. i.e. There are three cyan and magenta emulsions (layers) and two yellow emulsions (layers)".
4. A single layer may have several emulsions that have different characteristics. i.e. "The slow speed magenta layer has two emulsions".
5. In a single layer they may be different batches of the emulsion makes (batches). This allows blending to reduce variability in the final film. I.E. "A blend of 40% batch A and 60% batch B resulted in a speed of +/- .01 Log Exposure compared to the manufacturing sensitometric aim. .01 Log E is 1/30th of a stop.

To further the confusion Kodak and the rest of the photographic industry call "emulsions" what are actually "dispersions". What we called "dispersions" are actually "emulsions". This has a historical basis. Not a discussion I care to start. See a chemistry text.

www.makingKODAKfilm.com

Ian Grant said:

The Verichrome trade name predates its use by Kodak by a number of years, in fact it was a Wratten & Wainwright plate emulsion along with Allochrome and Wratten Panchromatic introduced around 1907/8. The original Verichrome was not Orthochromatic but along with Allochrome although not fully Panchromatic needed the same Wratten safelight as their Panchromatic plates.

I was talking to a member here last year who had a box of Verichrome plates, he thought from the 1930s, however George Eastman bought Wratten around 1912/3. After Mees & Sheppard moved to Rochester to found the Kodak Research facilities Kodak Ltd continued selling Wratten plates made by their Wratten division until around 1920/1.

Later 1931 Verichrome film-pack & roll film was Orthochromatic.

Ian

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Thanks for the English history.

And then there was Rollei R3 with 3 layers.

Ian Grant said:

The Verichrome trade name predates its use by Kodak by a number of years, in fact it was a Wratten & Wainwright plate emulsion along with Allochrome and Wratten Panchromatic introduced around 1907/8. The original Verichrome was not Orthochromatic but along with Allochrome although not fully Panchromatic needed the same Wratten safelight as their Panchromatic plates.

I was talking to a member here last year who had a box of Verichrome plates, he thought from the 1930s, however George Eastman bought Wratten around 1912/3. After Mees & Sheppard moved to Rochester to found the Kodak Research facilities Kodak Ltd continued selling Wratten plates made by their Wratten division until around 1920/1.

Later 1931 Verichrome film-pack & roll film was Orthochromatic.

Ian

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Thanks Ian for the clarification. I'm sure I was using the VerichromePan when I was first shooting with the Hassy 500C. All I know is that is was a very nice film developed in Microdol.

Ian Grant said:

The Verichrome trade name predates its use by Kodak by a number of years, in fact it was a Wratten & Wainwright plate emulsion along with Allochrome and Wratten Panchromatic introduced around 1907/8. The original Verichrome was not Orthochromatic but along with Allochrome although not fully Panchromatic needed the same Wratten safelight as their Panchromatic plates.

I was talking to a member here last year who had a box of Verichrome plates, he thought from the 1930s, however George Eastman bought Wratten around 1912/3. After Mees & Sheppard moved to Rochester to found the Kodak Research facilities Kodak Ltd continued selling Wratten plates made by their Wratten division until around 1920/1.

Later 1931 Verichrome film-pack & roll film was Orthochromatic.

Ian

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Thank you, I did not know that piece of Kodak and film history.

laser said:

To further the confusion Kodak and the rest of the photographic industry call "emulsions" what are actually "dispersions".

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Well, in a color film or paper, there's technically an emulsion together with a dispersion that's mixed in with a solution and the whole thing is then called an emulsion again...

Just put all the terminology in a food processor and emulsify the whole thing all at once.

DREW WILEY said:

Just put all the terminology in a food processor and emulsify the whole thing all at once.

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What time, temp and agitation speed is a good starting point?

Andrew O'Neill said:

Wow four layers! I had no idea.

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Not really, it's probably coated as 2 layers + supercoat. Delta 100 and 400 are (as far as known currently) single layer + supercoat, with Delta technology essentially focusing on using epitaxial growth techniques to both form high-aspect ratio crystal structures (which is different from how Tmax does things to the best of my knowledge, though Kodak has/ had extensive research into epitaxial techniques - see Maskasky et al - albeit that Kodak seems to only have commercialised epitaxy in areas like X-ray - and Fuji commercialised epitaxy in Acros, Provia 400X etc) with subsequent growth phases allowing for creation of of other crystal shapes on the extant high-aspect ratio crystals - thus allowing for a highly sensitive thin single layer structure that behaves more like a multi-emulsion, multi-layer structure (which has potential advantages in terms of sharpness and reduced internal reflections etc). I would argue that TMY-II is aiming at the same effective end in its use of T-grain and 3d crystal structures (i.e. effectively very controlled polydispersity), but possibly attempting to work around potential issues with epitaxial structures (and/ or patents/ IP), and with the benefit of having very advanced and efficient dye sensitising techniques available (whereas one of Ilford's claims about Delta was that it didn't need such advanced dye sensitising techniques and fixed more easily - make of that what you will...).

Andrew O'Neill said:

I've been using HP5-Plus for many years, and I've heard that it, like many 400 speed films, has two emulsions. A fast emulsion and a slow emulsion. What is not clear to me is are the two emulsions separate coatings, or are they combined, and coated as a single layer? I've heard that Bergger Pancro 400 has two emulsion... one consisting of silver nitrate, the other of silver iodide. Are they also mixed together or laid down separately? Does anyone know if HP5 uses both silver nitrate and silver iodide? Thank you!

andy

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Most films have several layers, some have mixed components as well. From what I understand, Delta 400 has the fast layer from Delta 100, and the slow layer from Delta 3200.