Tag: silver gelatin

Since we opened a door through salted paper to gellow and silver to be allowed in, we will continue with this kind of work.

This was thrilling. With this process we can print pictures in almost any kind of material. I don’t mean any kind of paper, I mean material! Glass, wood, stone, paper, plastic, fabric, you name it.

Let’s continue with our recipes, shall we?

Possible ingredients used in these emulsions:

• Watery veichle – Water and gelatine, were the cristals will be scattered
• Silver Halide – Silver bromide, silver iodide or silver chloride
• Anti veil – potassium bromide, wich pretty much avoids the development of a white “veil” on the image’s surface
• Anti fungus – Fenol
• Sensitizer agents – Active gelatine, gold salts, fixator in small amouts or dye. These will incfease the sensitivity to light.
• Hardening agents – Like formalin or chromium salts, they reduce the gelatin’s capacity to absorve water, this way, preventing it from slipping out of the material chosen (like it happened to me, but we will get there)
• Helping agents – wetting agent, glycerine, alcohol
• Plasticizer – these facilitate application of the emulsion in the surfaces chosen

How to “cook” liquid emulsion:

1^st – Precipitation – When through precipitation insoluble cristals are formed

2^nd – Maturation – the growth of the insolubl cristals takes place

3^rd – Washing – Pretty much just washing the excess of cristals

4^th – Post Maturation – The adding of gelatine, sensitizers and dyes (just like it is described in the ingredients)

But what happens, that turns gelatin into a light sensitive material you might ask?

At its heart silver gelatin photography is a kind of alchemy: light and chemistry are used to reduce light sensitive silver salts suspended in a gelatin emulsion into pure silver. During the manufacturing process ions of silver bonded to atoms of the halogen family (usually bromine, chlorine, iodine) form crystals of water insoluble silver salts, known as silver halides. These are suspended uniformly in a flexible gelatin emulsion which is coated on a transparent base.  Unlike their photographic predecessors, these crystals are shelf stable for long periods of time.

Once exposed to light the crystals absorbs the energy of photons. This energy causes atoms of metallic silver to build up flaws in the crystal. The more photons absorbed by the crystal the denser the cluster of silver atoms grows, forming a latent image, once enough silver has formed on the surface of the crystal it becomes something that you can develop.

Before we move on, you might ask is who the heck thought of ever using gelatin to fix photographs?

Well, that was Richard Leach Maddox. He was the first to invent a relatively stable silver gelatin and patent it (yes, someone had the same idea first and forgot to claim it in time). This emulsion could be coated on glass, so that photographers didn’t have to make their own light sensitive materials, and could be marketed, wich was brilliant.

Maddox’s need for inspiration came from becoming sick from the fumes produced by the mixing of the emulsion for wet collodion plates, that also had to be prepared and placed on glass immediately before exposure (if the emulsion turned hard or dry you would have to start over again).

Of course Maddox’s technique was only perfected to the point that it was sensitive enough for short exposures. Later coming out as negatives, that could be commercialized in a relatively cheap way, and so lauching photography as an art form anyone could do.

My take on emulsion

The process I used in class was supposed to be simple: we used commercial liquid emulsion and a surface of our own choosing. I chose glass (heads up, biggest mistake of my life).

We started preparing our materials for the emulsion. Those who had stone for example had to put a coating on it, glass had to be treated so it would have micro abrasions (we basically scratched it in circular movements using alcool, water and calcium carbonate dust), but the right fabrics or papers don’t require this prep has they already have fibers to wich the emulsion can grab itself on.

The place was equipped with red lighting, as the others expose constantly.

The emulsion has to be warm so it turns liquid, but we can’t just heat it directly because it will affect it’s components, loosing their sensitivity. So, in Portugal we call it “Banho-Maria” here let’s just say, contact heating. So you fill a tank with hot water and another tank with the commercial gelatin (do not use a metal spoon to take it of the jar, use glass or plastic has metal will interact with the silver), and then put the tank with the gelatin inside the one with the hot water. Evaluate it’s temperature until it’s between 35ºC-45ºC.

We all did the paper (Canson A3 cutted in smaller bits), because it is easyer to test on it the exposure time. To sensitize paper we folded it into little boats: folding each side in about 2-3 cm, and then the corners to the inside.

Now all that’s left to do is poor the emulsion in the surfaces, levelling those suefaces so the emulsion would be distributed equally. Run down the excess of emulsion back to the warming jar and save it in the fridge (so it goes hard again and doesn’t loose it’s proprieties).

Put dow the paper, glass, wood piece or whatever your using in a levelled surface and let it dry out in the dark. The emulsion will loose water and loose that relief you see, and then it will be ready to go into the light and expose.

The best and easiest kind of negative to use in this process is analog film, I used one I shot for another class, and put it in the amplifier.

Took the paper and ran some tests. So I put the paper under the amplifier and covered it with a black card, leaving only a stripe out and turned the amplifier on for 3 seconds, moved it a bit more to expose even more of the paper and did it again 3 secs more and so on, so on until the other edge of the image.

So I chose to expose my final image for the seconds correspondent to the layer that seemed to me had the best details. This is what I came up with.

I achieved nice contrast on the left side of the image, my face ‘though is lacking liquid emulsion, all the way to the bottom of the image to. And overall, this might not have been the best image choice i did so far… Sorry…

After exposing the glass (my own choice to use glass) it goes into the usual chemicals:

1. Developer – 30-90 seconds
2. Stopping bath – 30 seconds
3. Fixer – 10 minutes
4. Whashing – 30 minutes (changing the water regularly)

Sounds easy han? Well forget it.

For some reason that evades me completely, as soon as they where put inside the chemicals, the image started to peel off. It didn’t stick to the glass, it started floting around in the revealer (contaminating it for everyone else using it) and even if it didn’t completely peel of and by a miracle we would stay still holding the glass in the chemicals, it was peeling off some places else and the image would move around. So by the end of this, not only was it destroyed but also the corner of my image turned yeallowish, apparently form the excess of emulsion.

So in a bigger picture, glass was a total disaster (every other materials turned out fine). The image I chose may not also have been ther best idea (since my face was in the sun,  colleague was in complete shade and a middle colleague was half/half.
So to have a correct exposure, was barely impossible and the final result was, we only get the middle colleague and a bit of my chin. This part was my bad.

Still the teacher allowed me to print my image in emulsion on paper (since she noticed how low the moral around the lab was) and I managed to screw it up to, because my image was bad quality and I also put to much emulsion on the paper, so it turned yellow to. Disaster.

Some sources of information about liquid emulsions that are better at this than me:

Martin Reed and Sarah Jones wrote: Silver Gelatin – A users guide to liquid photographic emulsions

You can get this one at: https://www.amazon.co.uk/Silver-Gelatin-Liquid-Photographic-Emulsions/dp/1902538153

Leslie Stroebel, John Compton, Ira Current and Richard Sakia wrote: Basic Photographic Materials and Processes

References

Vener, E. (2017, November 2017). Silver Gelatin Photography: The Medium That Changed the World . Researched in November 19th, 2019 in: https://www.thephoblographer.com/2017/11/28/silver-gelatin-photography-the-medium-that-changed-the-world/

Ilford Photo (s.d.). History of Ilford Photo. Researched in November 15th, 2019 in: https://www.ilfordphoto.com/about-us/history/?___store=ilford_brochure&___from_store=ilford_brochure

Camilla Watson (s.d.). Priting Technique. Researched in November 15th, 2019 in: https://camillawatsonphotography.net/process/