Seeking Advice on Photosensitive Emulsion Application

Hi,

We are a theater company currently working on a new project that combines performance and photography.

Currently, we are operating in a black box environment with red lighting. We have positioned a performer in front of photosensitive material (using Rollei's liquid light) and exposed him to various light sources. Subsequently, we reveal the support using black and white chemistry with a glazing system.

Here are some aspects we appreciate about our current setup:

• Liquid light has the versatility to make a wide range of materials photosensitive. While we haven't finalized our scenic design, it will either involve a wooden structure covered with paper or fabric.
• Liquid light is white before exposure, unlike other chemistries used for anthotypes, making it inconspicuous and adaptable to our scenography.
• Both liquid light and the developer we utilize are non-flammable, making them safe for stage use.

However, a significant challenge we face is the need to reapply the photosensitive emulsion to our support every time we perform the show. This results in high production costs.

We are exploring the possibility of developing an emulsion with similar advantages but at a lower cost and, more importantly, easier application. Ideally, we would like to explore the possibility of applying the photosensitive solution with a spray, which could potentially streamline our process and reduce costs.

One member of this community kindly recommended that I delve into Denise Ross's "The Handmade Silver Gelatin Emulsion Print" for guidance. Additionally, I am here to seek your collective wisdom

The ultimate formula we aspire to achieve would possess the following attributes:

• Compatibility with red light.
• Pre-exposure whiteness or transparency.
• Liquid consistency to enable broad spray application for swift and optimal results.
• Non-flammability and stage-friendly safety.
• Suitability for exposure to LED/stage lighting and natural sunlight/UV.
• We are also curious about a potential elimination of the need for a developer, relying solely on light for the process?

If you have any insights or suggestions, we would greatly appreciate your input.

EV

You may find the most economic solution would be to buy a roll of wide photo paper from Ilford or Foma. That way, you wouldn't need to worry about making an emulsion - which is a specialized task and pretty expensive in itself. If you contacted Ilford (Harman Technology) or Foma directly and said what you were doing, you might get something direct from them at a discount.

Making a reasonably fast emulsion that easily sprays might be quite difficult. And I don't think it's possible to do away with developer in your application.

If you have sufficient UV in the stage lighting, you can do away with development requirement if you use a so-called print-out process like salted paper where the image appears as and when it is exposed. Application is much easier too. Just coat salt followed by silver nitrate (with appropriate precautions) and the surface is photo-active. The chemistry is also colorless. Cyanotype might be another possibility. In that case, the photosensitzer is yellow but it won't show much in red or yellow light, however it will turn green and then blue followed by gray as it is exposed to UV.

:Niranjan.

nmp said:

If you have sufficient UV in the stage lighting, you can do away with development requirement if you use a so-called print-out process like salted paper where the image appears as and when it is exposed. Application is much easier too. Just coat salt followed by silver nitrate (with appropriate precautions) and the surface is photo-active. The chemistry is also colorless. Cyanotype might be another possibility. In that case, the photosensitzer is yellow but it won't show much in red or yellow light, however it will turn green and then blue followed by gray as it is exposed to UV.

:Niranjan.

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Correct me if I'm wrong, but isn't the exposure required for printing out wildly impractical for the purpose in the OP, if that required for developing out emulsion works?

Just brainstorming as I munch my lunch ....

If you are just after a silhouette, which I presume you must be, and you are OK with UV-B stage lights Cyanotype is a possible printing out methods. I've see a workshop where someone lies on a sheet of fabric for a couple of minutes (commercial example: https://www.jacquardproducts.com/cyanotype-fabric-sheets). You could develop the image by spraying with water containing a little hydrogen peroxide and get a theatrical colour change. Making your own sensitizer would be very cheap and easy. It needn't look blue if you light it right.

There is also Argyrotype as a printing out process. It is an irritant but would be OK when coated and acts much like cyanotype. Develop and fix in mild citric acid and non toxic hypo. Again make your own once you have got it working. I've done this for regular photographic printing and it isn't that hard.

I've decided to stop making my own silver gelatine emulsion having made 28 batches over the last few years - maybe I'll come back to it when retire. Of those 28 batches I think I only had a couple of complete failures and I started out knowing nothing. Like playing the saxophone it isn't difficult to do badly! I think I worked out it cost me about £16 for 360ml of emulsion. Most of that was in the 10g of Silver Nitrate. That's about 1/4 the price of fotospeed liquid emulsion.

I guess it depends on how big and how often and how much labour and space and time you have.

Good luck with it.

You probably don't want performers standing under the brightest UV lights you can find for the 10 minutes or so required to get a pale image on printing-out-paper or cyanotype. Probably not a good idea to give them skin cancer after a couple of weeks of performance. (Exaggeration, I know.)

How permanent do you want the image to be? Must it be visible for minutes? An hour? Forever?

I ask because this reminds of a visual effect I've seen in science museums. A surface is painted with glow-in-the-dark paint. People can stand in front of it, and a bright strobe (flash) is fired. The painted surface briefly glows from the flash, and there are silhouettes where the people were blocking the light. It fades quickly, though.

Thank you for your valuable feedback,

Here is some additional information regarding the project:

Currently, we use various light sources such as stage LED lights, a candle flame, a video projector, and more to expose our current material. Restricting ourselves to UV lamps alone would limit us creatively and raise concerns about our performers' health.

We are seeking a distinct aesthetic from the cyanotype (even though lighting can alter its appearance). More importantly, we aim to capture the performer's shadow rather than an imprint on their body. With our current liquid light setup, the performer can be positioned around 100cm or more from the support, and the process works relatively quickly depending on the light source used for exposure. For instance, with a flash, the image appears in just 20 seconds, while with a candle, it takes longer (a few minutes), but this timing adds to the temporal dimension of our performance. We really enjoy mixing the different depths of the perfomers and sets in the space, as well as the different sources of exposure.

Furthermore, we appreciate that the image remains visible for at least a few minutes. We have not yet decided its fate: it may either endure indefinitely or, by illuminating the support with other light sources without fixing it, the image turns black and disappears.

To sum up, the key criteria that matter to us are as follows:

• The absence of a need for UV light.
• The ability to work with the performer's and set's shadows.
• Ensuring that the exposure time is not excessively long while still producing a contrasted image.
• While fixing the image is not a priority, it should remain visible to the audience for at least a few minutes.

What do you you think? Thanks again for your feedbacks !

I think there isn't any material that works in that range of exposure with visible light, other than what you're using and variations thereof (albumin instead of gelatine maybe?) and ready-made darkroom printing paper, as suggested in the first response. All the so-called alternative processes use UV.

EliseV said:

While fixing the image is not a priority, it should remain visible to the audience for at least a few minutes.

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If you want the image to stay for some length of time, rinse it with water after developing (using whatever it is you're currently using). That will delay development but not totally stop it. If you then wanted to quickly develop out the newly exposed parts, you could still do so. That way you could have the white silhouette visible for as long as you practically wanted then make it almost immediately turn black by reapplying developer.

Don_ih said:

You may find the most economic solution would be to buy a roll of wide photo paper from Ilford or Foma.

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This would be by far the most practical and likely also cost-effective approach. The main limitation is the maximum roll width, although two (or more) bands of paper could be tacked/stapled/pinned side by side to a panel if a larger area needs to be covered.

RogerHyam said:

UV-B stage lights

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Fortunately, all alt. printing processes work fine with UV-A. UV-B is the band that starts at something like 350nm, downward. You really don't want to cast any significant amounts of UV-B onto players or an audience - especially the players would receive levels of exposure that with UV-B would be really problematic, especially for their eyes (look up 'Klieg eyes'). Having them wear sunglasses would help.

Anyway, all UV-sensitive alt. printing processes are really far too slow for this application, so that's a dead-end street to begin with.

As to the idea of coating a more common silver halide emulsion, the following scenarios come to mind:

1: Pre-coat several sheets of cloth or whatever it is that the stage design requires in a batch-wise fashion. Then use one sheet for each performance. Coating, storage and mounting of the coated sheets would have to be done under safelight conditions. The bath-wise coating of sheets would likely be a little more efficient and thus less costly than doing it one at a time for each performance (it's also less disruptive to the work schedule, I imagine).

2: Modify the existing gelatin-based emulsion to a spray coat application approach. There's two ways I can potentially see this working, at least at a theoretical level:
2a: Spray coat a warm emulsion so it remains liquid. The most practical (insofar we can call it that) way of doing this would be to work in a heated cabin (e.g. 45C) so that everything the emulsion touches remains above the melting point of the gelatin. A challenge would be to bring the coated sheet outside the coating chamber for it to cool down, set and dry. Another challenge is that even at elevated temperatures that are already very uncomfortable to work in, the rheology of the emulsion will likely present severe problems for spray application.

2b: Dilute an existing gelatin-based emulsion in a molten state with demineralized water, to a level where the cooled-down emulsion remains liquid and sprayable. Gelatin solutions tend to be liquid at low percentages of e.g. 0.2% - I imagine a dilution of at least 1+50 to 1+100 of the commercial product would be necessary to obtain a sprayable emulsion. Application would then be done by spraying many consecutive layers of emulsion, drying in-between, until the desired density is reached. Evidently, the repeated spray coating of the same sheet would be very time consuming.

3: Design an entirely new emulsion from the ground up, replacing the gelatin with another colloid. Coincidentally, someone has been inquiring into this on this forum https://www.photrio.com/forum/threads/can-anyone-help-me-make-emulsion-without-gelatine.201485 The gist of that thread, however, is that there are lots of ideas, lots of challenges, and it's all still firmly in the paper-napkin phase, not to mention that spray coating is not a requirement in that scenario, which would pose an additional set of profound challenges.

One thing that comes to mind is that the requirement of spray coating is pretty much antithetic to the nature of a silver halide emulsion. Such an emulsion in practice is really more of a suspension, and concentrated suspensions tend to spray very badly due to their high viscosity. Performing the R&D to solve this fundamental issue sounds quite unrealistic as a work package within a theatrical production. It's the kind of thing you'd expect a firm like FUJIFILM to dedicate money on - and they certainly would have, if it had made any economic sense (which it apparently doesn't!)

So that's a long way of saying: give @Don_ih's idea above a thought. It's the best shot you've got.

I have nothing to add to the technical discussion here. But I wanted to say---please post video of the resulting performance!!!

As mentioned alternative process methods are too slow for your performance related application and you want to avoid UV lighting. Could a version of the following work? -

Buy a box of 100 sheets of 10" X 8" and under red safe lighting pass them all through a tray of print developer and allow to dry in the dark. When dry and still under red safe lighting, lay them emulsion side down onto a large piece of black lightproof plastic and tape them together on the back to the required size of performance area. Place on vertical support still covered. You can the reveal as performance takes place, which should expose and develop and finally fog to black. You would need to experiment with single sheets to see if this or a variation may work.

Thank you very much for your time and these valuable ideas. I think that for the time being we will continue to experiment with gelatin-based emulsion, as recommended by koraks, and keep the photo paper as a last resort (as this would particularly reduce the possibilities for the scenography of our show...). I'll be sure to keep you posted on our progress over the coming months. Thanks again !

Old thread but I just stumbled across it - couple thoughts if you haven't dialed this in yet -

You mentioned "Rollei" and "Liquid Light", which are two different products. Rockland makes LL, it's not a really great product, low contrast and poorly packaged. FomaSpeed is very popular and the one many people come around to over time. Never tried the Rollie, seems it's like 2x the cost of Foma or LL.

Red-gelled stage lights may fog the paper; even narrow bandwidth LEDs will fog Fomaspeed fairly quickly, so test test test.

I spray Fomaspeed onto large canvases with a compressor and HVLP gun. Takes 3-4 coats since it lays it on fairly thin, but canvas isn't an even surface; a smooth surface may take less. I warm the emulsion up and keep the spray gun's bottle warm between coats. You'd want to protect the work area with plastic, have excellent ventilation, and wear a high-quality respirator. You might get a roll of black construction plastic and rig up a spray booth. A house fan will help set each coat faster than just air drying. Clean the gun REALLY WELL between coats, spray a lot of warm water through it. I don't thin or modify the emulsion in any way, though I add a small bit of the included hardener.