Monday, June 30, 2014

New55 at 10,000X

The world of the really small, too small for us to see unaided, is the province of the microscopist. The microscope, as you surely know, allows us to see details that we could never imagine and has had countless uses in medicine, industry and science.  There are dozens of types of microscopes, optical, acoustic, fluorescent, field emission and scanning electron, to name but a few.  Today we used the scanning electron microscope (SEM) to look at the edge of a receiver sheet - that's the white paper where instant positive photographs form, and it is quite a complex thing.

The receiver sheet as described by Andre Rott and Edith Weyde contained nuclei - mainly of metals and metallic salts - suspended in the top layer of paper, or any substrate.  When contacted by the processing chemical, and an exposed negative, the interchange of ionic silver, solvents, and sulfides occur in a rapid, battery-like process.  Electrical charges, yes. The "electrolyte" is not that different than most alkaline batteries, except that is a developer and a fixer, too.

The silver halide in the exposed negative represents one "terminal" of the circuit. What is the second? In the fast-paced world of Diffusion Transfer Reversal, otherwise known as instant photography, it is the receiver paper, or more exactly, minute metals or metal salts and precursors, that form the second "electrode".  Those who are familiar with battery technology are sure to ask "which is the cathode, and which is the anode?" It depends.

Below are two SEM images obtained just today that show the various receiver sheet layers. Stacked like a cake, but made of paper, then a baryta coat, then acid layers, a timing layer, a nucleation layer, and finally a top, or release layer (to prevent sticking).  New55 FILM needs to make this or something like it. It's a daunting task as there are no recipes and even if there were, perhaps from patents and scientific papers, there'd still be a lot of process information. So we have over the last month started on the development of these layers, beginning with our visit to Colorado, where coaters capable of coating so-called "solvent coats" meaning, not water-based, but instead based on alcohols, acetone, or some other solvent. That was just the start: Now, every day, the coating team formulates at least one or two experiments, tests them, and decides on the next experiment.

The value of an SEM is hard to overestimate, and I would like to have one close, in our lab.

Baryta, then cellulose acetate, acid layer and other layers

The nucleation layer. We barely see the tiny nanoparticles.

















3 comments:

Jakelovesphoto -Jake Fleming- said...

I'm quite certain you've looked through every early polaroid patent, but just in case, here: http://www.google.com/patents/US2653527 describes exactly what to put on the receiver paper, (and unlike most of the chemicals Land references, its all still made).
"A sheet of bond paper 22 [22 is a reference to a schematic image within the patent] is run through a bath containing by weight 10% cadmium acetate, 1% lead acetate and 30% zinc nitrate, the sheet being in contact with this bath for about 30 seconds"

Bob Crowley said...

Jake, thanks I have. FYI that patent is not about a modern receiver paper. In addition, it used cadmium and lead, so, not something that can be easily done these days. It also does not work! Land was notorious for failing to provide a complete enablement in patents and Polaroid's patent practices were part of the stimuli for later changes to the patent syste. (which is not any better today, perhaps even worse for the small inventor). The missing part relates to what is needed to produce a neutral tone with a good Dmax. Also this would not produce a permanent image - it would fade in a few weeks. This is a good recipe for someone at home who 1. isn't afraid of heavy metals, and 2. wants to see a result that is not necessarily permanent. BTW this is similar to that described earlier by Rott and Weyde of Agfa some years earlier.

Bob Crowley said...

Andrew said

Wow..no idea it was so complicated. ...thought id stop by and check up on progress.
To go with my 545 back I have now purchased a Sinar F...

Andrew Bartram @Warboyssnapper Cambridgeshire UK