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- Sep 24, 2009
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For the last few months I have been experimenting with diffusion transfer printing and have some results to share, in case anyone is interested to repeat them.
The concept at work here is that an exposed but undeveloped film sheet is superposed face-to-face on a receiver sheet, with a chemical developing paste spread in a thin layer between. The film develops simultaneously as undeveloped silver diffuses across the gap and condenses onto the receiver sheet forming a positive image. This process was invented/discovered in the 1920s but significantly advanced and famously popularized by Edwin Land and the Polaroid Corporation from the late 1940s, being commercialized in the Polaroid 95 camera and subsequent models.
Following the demise of the original Polaroid Corporation the concept was re-worked by the late Bob Crowley in a crowdfunded way a decade or so ago under the guise of the New55 project. As far as I am aware this is currently on hiatus, and no technical details of his work are available, because $$$$. In fact there are no other serious public domain recipies for this process that I can find.
Presented here is a tested process, but achieving repeatable results has taken me a long time. There are many many variables that affect image quality (or in fact whether you get an image at all) and until you know what they are, you can't control for them. So you get a lot of apparently random successes and failures, and trying to isolate what makes the difference is a challenge.
Materials:
For film - I have been using Ilford RC Multigrade Deluxe 5x3.5" paper, exposed at EI 2-4. Paper is cheaper than film and orthochromatic so one can work under safelight.
Receiver paper base: Staples own brand 6x4 glossy inkjet paper, 10.4mil (0.264mm) thickness.
Epson Premium Photo Paper Glossy also works. They are both a good quality base with a layer of a plastic polymer which receives gelatin well.
The following chemicals are used (with suggestions for suppliers):
zinc nitrate - chemical supplier
sodium sulphide - photographic chemical supplier
Polysorbate 20 (PS20) - amazon.com
gelatin - amazon.com
glyoxal - chemical supplier
polyvinypyrrolidone (PVP) - Ebay
sodium carboxymethylcellulose (CMC) - ingredientdepot.com
sodium sulfite - photographic chemical supplier
sodium hydroxide - hardware store
sodium thiosulphate - photographic chemical supplier
hydroquinone - ditto
ascorbic acid - health food store
Materials are mostly specified by weight as even a cheap milligram scale makes it easy to be accurate. Quantities given in ml are dispensed by pipette.
I have used both supermarket distilled water and tap water without any obvious distinction in results between them. The tap water suppyl here is light on ionic content, the most problematic from a photographic process being a level of chloride ions. However that doesn't seem to affect this process.
I have also used both (quality) culinary gelatin and photographic gelatin without observable difference.
Receiver paper (recipe 80)
Phase A
15g 0.5% PVP (optional, otherwise 15g water)
1ml 1% sodium sulfide
2 drops 10% PS20
Phase B
15g 0.5% PVP (optional, otherwise 15g water)
1ml 25% zinc nitrate
2 drops 10% PS20
Phase C
30g 6% gelatin solution
1ml glyoxal
Dump phase A into phase B and mix briefly. Add to phase C.
Plate on receiver paper with a 100 micron wire bar coater (aliexpress.com) about 1ml per sheet. Dry.
Developer (recipe 114)
60g 2% CMC (optionally 1%)
1.2g sodium hydroxide
1.2g sodium sulphite
0.3g sodium thiosulphate
Mix well with a small resin mixer paddle (amazon.com) in a battery hand drill (Dewalt) approximately 60 seconds. Then add:
0.5g ascorbic acid
1.0g hydroquinone
Mix further well until disolved - approximately another 60 seconds. Pour into a 100ml plastic syringe (amazon.com). Insert the syringe plunger a few mm into the syringe body to act as a plug and invert so the nozzle is upwards. When the trapped air pocket reaches the top, slide the plunger in further to expel all the air.
Note: The developer browns (oxidzes) rapidly while exposed to air. Once the air is removed from the syringe and the syringe is capped it will keep indefinitely.
Processing:
A good image requires an exactly even layer of developer between the receiver sheet and the film. Therefore thickness guide rails are mandatory. I found that the lid of a party-size pre-prepared vegetable selection tray (the one with the cheese dip in the middle) is PET film 0.59mm thick. The Ilford photo paper ("film") and inkjet paper ("receiver") together are 0.50mm. I cut a U-shaped guide from of the PET film with a 4" gap between the arms of the U. It therefore functions as a rolling guide to create a 0.09mm layer of developer between film and receiver. You can experiment with reduced thicknesses by adding one or more layers of aluminium foil under the paper to pad out the film/developer/receiver sandwich.
The development is achieved between two pieces (or inside one large folded piece) of aluminium foil. And should be done an extremely flat surface, such as a sheet of glass. Place the receiver paper on the foil between the arms of the guide face-up. Syringe about 1 to 1.5ml of developer in a rough line across the receiver paper close to one of the short edges. Under safelight, orient the film to be developed/printed face down with the strip of developer across one end. Cover with the second sheet of foil (or fold the top of the foil over).
Spread the developer by rolling down the length of the guide with a straight smooth metal tube. A rubber printing roller is sufficiently not-straight to give an uneven layer of developer and therefore poor or no results. You are hoping for an even layer of developer less than 0.09 mm thick, or thinner. For good results the table, roller, and mechanism of rolling must be both flat and even to a significantly higher level of precision than this.
Once the rolling is complete and the aluminum foil is pressed over the assembly, you can continue in room light.
After 60 seconds separate the developer and film. Wash the receiver paper immediately under tepid running water.
Notes, in no particular order:
CMC solutions as required above (1% or 2%) are best prepared under high shear mixing - also known as a KitchenAid blender - running for a duration of a few minutes. Make it up 1 litre at a time. Entrapped bubbles will float out after a few hours.
Image density is increased by increasing the level of silver solvent (thiosulphate) in the developer. Increasing the image density too far appears to give "holes" in the image due to some crystallization (or other) effect. Unfortunately this week I had to drop off both of my scanning electron microscopes for repair so I can't investigate yet.
Image tone and colour depend on the nature, size and concentration of the condensation nuclei in the receiver paper. In the recipe given above these are nanoparticles of zinc sulphide. (However be aware that the excess of zinc ions is also a required part of the process.) The formation of the nanoparticles occurs when you mix phases A and B (above). There is a huge variety of different ways to not get good nucleation sites when combining different quantities and concentrations of zinc nitrate and sodium sulphide. The suggestions above give (me) a dark red image tone (typical of colloidal silver) which fades to a sepia brown after drying. I have also achieved more neutral tones as well as brighter yellows, darker browns and others. 90% of the effort of this project has been to find a repeatable way to provide good nucleation.
The shelf life of the receiver coating mix and the paper itself is (likely) limited to the order of hours or a small number of days. Over time the zinc sulphide nanoparticles have a tendency to aggregate, which spoils the resulting image.
There are a bazillion other reagents and methods that will give nucleation particles. I am still working through a long list of suggestions from the literature.
There are also a bazillion different ways to support those nucleation sites other than gelatin. For one suggestion, soak the receiver paper as-supplied in 2% sodium hydroxide for 2 minutes, rinse and dry. Then dip briefly in the mixture of phase A and phase B above to adsorb the nucleation particles onto the swelled polymer layer. Dry. Process the same way.
Land used a layer of silica particles as a layer which (according to patents) gave a more neutral image tone. I have made many efforts to produce results with various commercially available silica preparations with no good results to report. Yet.
The literature suggests that neutral image tones can be achieved by incorporating thiols (historically, mercaptans) such as cysteine and 5-Mercapto-1-phenyl-1H-tetrazole. I have had no success with these either. Again, yet.
Stripping layer:
One of the goals of a peel-apart print is to avoid having to wash the print after development. If this is your goal you can try coating this stripping layer over the image layer:
3% gum arabic (amazon.com)
6% aluminium lactate (Etsy)
A really effective stripping layer is still work-in-progress. The more layers that you need to coat, the harder it gets to generate an even image, since any variation in layer thicknesses invariably affect development. This is an area where commercial laboratories (with automated coating machines) can generate results difficult to achieve with hand-coating methods. Land's films had many layers, as reading some of his later patents will show.
If I were trying to create a monochrome instant film starting from scratch today, and I had the resources of a good organic synthesis laboratory, I wouldn't bother with trying capture undeveloped silver; I'd try to find one or more organic dye-developers to use much like the peel-apart colour films, except formulated to give a monochrome image. Silver just seems too difficult to control.
I will post some photographs of results and materials subsequently.
Resources:
Book: Photographic Silver Halide Diffusion Processes (André Rott, Edith Weyde)
Book: Handbook of Photography and Reprography: Materials, Processes and Systems (Caroll B. Neblette) - particularly chapter 7 on one-step imaging, written by Edwin Land himself describing his work and improvements to the diffusion transfer process. I wonder if he had fun referring to himself in the third person.
The US patent database has literally hundreds of relevant patents. Particularly useful is everything filed by Meroë Morse who was Land's chief scientist on monochrome instant imaging. Other than Polaroid, there are relevant entries from Agfa and Kodak, as well as others. Some entries in the European and Canadian patent databases have been helpful too.
A huge number of online papers (particularly) on the creation and stabilization of nanoparticles of different varieties are available.
Final note:
I have been greatly assisted by the prolific suggestions and postings of two former contributors to this and other photographic forums, those people being Rowland Mowrey and Patrick Gainer, both of blessed memory. Although I never met or conversed with either, what they have left behind online has been both inspirational and motivational for me. May their memories (continue to) be a blessing.
The concept at work here is that an exposed but undeveloped film sheet is superposed face-to-face on a receiver sheet, with a chemical developing paste spread in a thin layer between. The film develops simultaneously as undeveloped silver diffuses across the gap and condenses onto the receiver sheet forming a positive image. This process was invented/discovered in the 1920s but significantly advanced and famously popularized by Edwin Land and the Polaroid Corporation from the late 1940s, being commercialized in the Polaroid 95 camera and subsequent models.
Following the demise of the original Polaroid Corporation the concept was re-worked by the late Bob Crowley in a crowdfunded way a decade or so ago under the guise of the New55 project. As far as I am aware this is currently on hiatus, and no technical details of his work are available, because $$$$. In fact there are no other serious public domain recipies for this process that I can find.
Presented here is a tested process, but achieving repeatable results has taken me a long time. There are many many variables that affect image quality (or in fact whether you get an image at all) and until you know what they are, you can't control for them. So you get a lot of apparently random successes and failures, and trying to isolate what makes the difference is a challenge.
Materials:
For film - I have been using Ilford RC Multigrade Deluxe 5x3.5" paper, exposed at EI 2-4. Paper is cheaper than film and orthochromatic so one can work under safelight.
Receiver paper base: Staples own brand 6x4 glossy inkjet paper, 10.4mil (0.264mm) thickness.
Epson Premium Photo Paper Glossy also works. They are both a good quality base with a layer of a plastic polymer which receives gelatin well.
The following chemicals are used (with suggestions for suppliers):
zinc nitrate - chemical supplier
sodium sulphide - photographic chemical supplier
Polysorbate 20 (PS20) - amazon.com
gelatin - amazon.com
glyoxal - chemical supplier
polyvinypyrrolidone (PVP) - Ebay
sodium carboxymethylcellulose (CMC) - ingredientdepot.com
sodium sulfite - photographic chemical supplier
sodium hydroxide - hardware store
sodium thiosulphate - photographic chemical supplier
hydroquinone - ditto
ascorbic acid - health food store
Materials are mostly specified by weight as even a cheap milligram scale makes it easy to be accurate. Quantities given in ml are dispensed by pipette.
I have used both supermarket distilled water and tap water without any obvious distinction in results between them. The tap water suppyl here is light on ionic content, the most problematic from a photographic process being a level of chloride ions. However that doesn't seem to affect this process.
I have also used both (quality) culinary gelatin and photographic gelatin without observable difference.
Receiver paper (recipe 80)
Phase A
15g 0.5% PVP (optional, otherwise 15g water)
1ml 1% sodium sulfide
2 drops 10% PS20
Phase B
15g 0.5% PVP (optional, otherwise 15g water)
1ml 25% zinc nitrate
2 drops 10% PS20
Phase C
30g 6% gelatin solution
1ml glyoxal
Dump phase A into phase B and mix briefly. Add to phase C.
Plate on receiver paper with a 100 micron wire bar coater (aliexpress.com) about 1ml per sheet. Dry.
Developer (recipe 114)
60g 2% CMC (optionally 1%)
1.2g sodium hydroxide
1.2g sodium sulphite
0.3g sodium thiosulphate
Mix well with a small resin mixer paddle (amazon.com) in a battery hand drill (Dewalt) approximately 60 seconds. Then add:
0.5g ascorbic acid
1.0g hydroquinone
Mix further well until disolved - approximately another 60 seconds. Pour into a 100ml plastic syringe (amazon.com). Insert the syringe plunger a few mm into the syringe body to act as a plug and invert so the nozzle is upwards. When the trapped air pocket reaches the top, slide the plunger in further to expel all the air.
Note: The developer browns (oxidzes) rapidly while exposed to air. Once the air is removed from the syringe and the syringe is capped it will keep indefinitely.
Processing:
A good image requires an exactly even layer of developer between the receiver sheet and the film. Therefore thickness guide rails are mandatory. I found that the lid of a party-size pre-prepared vegetable selection tray (the one with the cheese dip in the middle) is PET film 0.59mm thick. The Ilford photo paper ("film") and inkjet paper ("receiver") together are 0.50mm. I cut a U-shaped guide from of the PET film with a 4" gap between the arms of the U. It therefore functions as a rolling guide to create a 0.09mm layer of developer between film and receiver. You can experiment with reduced thicknesses by adding one or more layers of aluminium foil under the paper to pad out the film/developer/receiver sandwich.
The development is achieved between two pieces (or inside one large folded piece) of aluminium foil. And should be done an extremely flat surface, such as a sheet of glass. Place the receiver paper on the foil between the arms of the guide face-up. Syringe about 1 to 1.5ml of developer in a rough line across the receiver paper close to one of the short edges. Under safelight, orient the film to be developed/printed face down with the strip of developer across one end. Cover with the second sheet of foil (or fold the top of the foil over).
Spread the developer by rolling down the length of the guide with a straight smooth metal tube. A rubber printing roller is sufficiently not-straight to give an uneven layer of developer and therefore poor or no results. You are hoping for an even layer of developer less than 0.09 mm thick, or thinner. For good results the table, roller, and mechanism of rolling must be both flat and even to a significantly higher level of precision than this.
Once the rolling is complete and the aluminum foil is pressed over the assembly, you can continue in room light.
After 60 seconds separate the developer and film. Wash the receiver paper immediately under tepid running water.
Notes, in no particular order:
CMC solutions as required above (1% or 2%) are best prepared under high shear mixing - also known as a KitchenAid blender - running for a duration of a few minutes. Make it up 1 litre at a time. Entrapped bubbles will float out after a few hours.
Image density is increased by increasing the level of silver solvent (thiosulphate) in the developer. Increasing the image density too far appears to give "holes" in the image due to some crystallization (or other) effect. Unfortunately this week I had to drop off both of my scanning electron microscopes for repair so I can't investigate yet.
Image tone and colour depend on the nature, size and concentration of the condensation nuclei in the receiver paper. In the recipe given above these are nanoparticles of zinc sulphide. (However be aware that the excess of zinc ions is also a required part of the process.) The formation of the nanoparticles occurs when you mix phases A and B (above). There is a huge variety of different ways to not get good nucleation sites when combining different quantities and concentrations of zinc nitrate and sodium sulphide. The suggestions above give (me) a dark red image tone (typical of colloidal silver) which fades to a sepia brown after drying. I have also achieved more neutral tones as well as brighter yellows, darker browns and others. 90% of the effort of this project has been to find a repeatable way to provide good nucleation.
The shelf life of the receiver coating mix and the paper itself is (likely) limited to the order of hours or a small number of days. Over time the zinc sulphide nanoparticles have a tendency to aggregate, which spoils the resulting image.
There are a bazillion other reagents and methods that will give nucleation particles. I am still working through a long list of suggestions from the literature.
There are also a bazillion different ways to support those nucleation sites other than gelatin. For one suggestion, soak the receiver paper as-supplied in 2% sodium hydroxide for 2 minutes, rinse and dry. Then dip briefly in the mixture of phase A and phase B above to adsorb the nucleation particles onto the swelled polymer layer. Dry. Process the same way.
Land used a layer of silica particles as a layer which (according to patents) gave a more neutral image tone. I have made many efforts to produce results with various commercially available silica preparations with no good results to report. Yet.
The literature suggests that neutral image tones can be achieved by incorporating thiols (historically, mercaptans) such as cysteine and 5-Mercapto-1-phenyl-1H-tetrazole. I have had no success with these either. Again, yet.
Stripping layer:
One of the goals of a peel-apart print is to avoid having to wash the print after development. If this is your goal you can try coating this stripping layer over the image layer:
3% gum arabic (amazon.com)
6% aluminium lactate (Etsy)
A really effective stripping layer is still work-in-progress. The more layers that you need to coat, the harder it gets to generate an even image, since any variation in layer thicknesses invariably affect development. This is an area where commercial laboratories (with automated coating machines) can generate results difficult to achieve with hand-coating methods. Land's films had many layers, as reading some of his later patents will show.
If I were trying to create a monochrome instant film starting from scratch today, and I had the resources of a good organic synthesis laboratory, I wouldn't bother with trying capture undeveloped silver; I'd try to find one or more organic dye-developers to use much like the peel-apart colour films, except formulated to give a monochrome image. Silver just seems too difficult to control.
I will post some photographs of results and materials subsequently.
Resources:
Book: Photographic Silver Halide Diffusion Processes (André Rott, Edith Weyde)
Book: Handbook of Photography and Reprography: Materials, Processes and Systems (Caroll B. Neblette) - particularly chapter 7 on one-step imaging, written by Edwin Land himself describing his work and improvements to the diffusion transfer process. I wonder if he had fun referring to himself in the third person.
The US patent database has literally hundreds of relevant patents. Particularly useful is everything filed by Meroë Morse who was Land's chief scientist on monochrome instant imaging. Other than Polaroid, there are relevant entries from Agfa and Kodak, as well as others. Some entries in the European and Canadian patent databases have been helpful too.
A huge number of online papers (particularly) on the creation and stabilization of nanoparticles of different varieties are available.
Final note:
I have been greatly assisted by the prolific suggestions and postings of two former contributors to this and other photographic forums, those people being Rowland Mowrey and Patrick Gainer, both of blessed memory. Although I never met or conversed with either, what they have left behind online has been both inspirational and motivational for me. May their memories (continue to) be a blessing.
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