DIY developing process

04-01-2023 

︎ process


Materials:
- light-sensitive material such as photographic paper or photographic film with the previously captured images,
- substance high on phenolic acids (e.g. instant coffee, tea, plants, urine),
- washing soda (waterfree powder of sodium carbonate),
- vitamin C (pure ascorbic acid),
- water (distilled or tap),
- vinegar (4-6% acetic acid in water),
- photographic fixer (hypo or ammonium thiosulfate),
- 3 trays and 3 pegs (for developing a paper under a safe light),
- or a developing tank (for developing a film) with a dark bag for loading the film,
- gloves,
- string and clips for hanging developed photographs/films.

The recipe for 0,5L Caffenol-C (coffee-based ‘soup’) that I learnt in 2018 from internet is as follows:
- 27g of waterfree washing soda dissolved in 1/3 of 0,5l water
- 8 g of vitamin C dissolved in 1/3 of 0,5l water
- 20g of instant coffee dissolved in 1/3 of 0,5l water

We can mix ingredients in separate containers and then mix them together in the given order. For example, in case of Caffenol-C recipe, the order of mixing would be solution with soda -> solution with the vitamin C -> and solution with the instant coffee.

After I learnt the standard recipe, I started to experiment with my own adaptations. For example, I would lower the amount (20g of soda and 5g of vitamin C) which I found sufficient for developing process. I would start using ground coffee collected from local café instead of instant coffee with the hot water poured over and let it sit for a bit. Or I would reuse the second brew from my herbal tea, soaked any plants or berries, or my morning urine. In this case I would dissolve soda in the solution of my chosen liquid and then I would add vitamin C.

Developing times will vary according to the material and developer (for developing the film, I recommend to do a drop test). Temperature of the DIY plant-based developer is 20 degrees Celsius (as in standard developing) but I would encourage to experimenting because higher temperature can be more desirable. Somewhere between 20 and 24 degrees Celsius will do fine.

By measuring the pH of your solution you can check if the developer is enough alkaline (I would say it should be at least 10).

Plant-based developer:
For one 35mm film, the plant-based matter is extracted in cca 500ml of hot water (the extractions can vary between 1 hour to many hours). After the extraction is completed and the ingredients are sieved, divide the liquid into three equal parts:
- 20g of waterfree washing soda dissolved in one 1/3 of the liquid,
- 5 g of vitamin C dissolved in another 1/3 of the liquid,
- and mix these parts in the given order: soda solution, vit c solution, rest of the solution.

Simple version:
For one 35mm film, pour cca 500ml of hot water over the plant-based matter and let it cool down. After the extraction is completed and the ingredients are sieved, put:
- 3 table spoons of waterfree washing soda,
- 1 table spoon of vitamin C,
- and mix properly.

Developing film in a tank:
10 initial agitations and 3 agitations every minute. then rinsed with water with two tablespoons of vinegar (agitated 3 times), then rinsed with water (agitated 3 times), then again rinsed with water (and agitated 3 times) - that would take about a minute. Then applied fixer with 10 initial agitations and 3 agitations every minute for about 5 minutes. Then rinsed 10 times with water and 10 agitations.

Ingredients and my notes will be further explained. For self-study, I recommend sources such as The Caffenol Cookbook, or CuriosoLab or The Sustainable Darkroom network. For Czech speakers also research made by Georgy Bagdasarov whose thesis about developing film under difficult conditions was very influential.

LIGHT-SENSITIVE MATERIAL

Light-sensitive material is a material that is sensitive to the exposure of light. It contains silver salts (silver halides) that are bonded with the gelatine on the support material. Conventionally available material is usually paper-based or plastic-based. With the DIY developer, we can develop photographic paper for b&w chemistry, or any photographic film, however colour will not develop as a traditional colour film.


During the developing process, the image which was previously created with light is hidden in the layers of the light-sensitive material (it is latent). Through the developing process, the image appears on the surface. In chemistry this is called redox – which means that the oxidation state of the substance changed; the substance started to decompose; in photography it means that the silver salts were reduced to silver metal.

In fact, the redox reaction has already happened when the light hit the light-sensitive material, but it was not strong enough to create a visible image (only a prolonged exposure to the light would reduce the silver salts into the metallic form, or we can say that on light the silver salts would decompose into the silver metal). To avoid the exposure of the light-sensitive material, the safe light is used in the darkroom (usually safe red light, but the type of light is chosen according to the light-sensitive material as stated in the data sheet).

When the black and white light-sensitive material is placed into the developer, the chemical/photographic reaction happens quicker in the places which were exposed to the light thus on the photographic material we see that the parts with more light are black (darker), in contrast, parts exposed less are whiter (lighter). 

DIY developer must contain developing agents which are strong enough to reduce silver salts into metallic form and convert a latent image into visible one following exposure to the light.

PHENOLIC ACIDS

The common commercial photographic developer is based on the organic compounds that are derived from benzene. For example, Ilfosol 3 film developer is made of 1-Phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone, hydroquinone and sodium carbonate, Kodak D76 film developer contains sodium sulphite, hydroquinone, Bis(4-hydroxy-N-methylanilinium) sulphate, pentetic acid, pentasodium salt, boric anhydride. In both examples, hydroquinone contains benzene ring. Benzene is organic chemical compound which contains 6 atoms of carbon and each of them is connected to 1 atom of hydrogen.

The DIY photographic developer prepared from plants/food ingredients/waste ingredients contains phenolic acids which are phenolic compounds structured on the benzene ring. Preparing developer from coffee or plants such as mint or wild thyme, the developing power is delivered through the high content of phenolic acids such as e.g. caffeic acid. High content of phenolic acids is also present in urine as phenolic compounds that cannot be absorbed by the body are released out.

There are multiple techniques how to extract phenolic acids from the plants. We can pour hot water over and let the solution to cool down, or boil the plants in water on stove, or use a cold extraction method called maceration (in water, oil, alcohol) during which the plants and the liquid are stored at a room temperature in an air-tight container at least for 3 days and the desired compounds release into the liquid. Never boil plant tissue in alcohol on stove because it is highly flammable...You can freeze plants and use them later.

ALKALI

Another important ingredient in the DIY developer is alkali. Developing process goes on in the environment with ph>7. Alkali helps to achieve more contrast image but also a bigger grain. A common alkali used in the photographic developing process is a sodium carbonate aka washing soda. Washing soda can be bought as monohydrate or decahydrate in form of crystals or waterfree in form of a powder. In case the washing soda is not waterfree, the amount in the recipe needs to be multiplied by 1.2 (monohydrate) or 2.7 (decahydrate). If you are not sure what type of the soda you got, measuring the temperature of the solution can tell if it is waterfree soda because waterfree soda rises the temperature of water, while decahydrate lowers the temperature.

Besides sodium carbonate, another alkali is sodium bicarbonate which is, however, weaker than washing soda. By heating up sodium bicarbonate, it starts to decompose into sodium carbonate, water and carbon dioxide (thus if this should be done at home, the space needs to be well ventilated). Strong alkali is e.g. sodium hydroxide which is used in the households products for drain cleaning but it is highly caustic and not particularly friendly to aquatic life.

ASCORBIC ACID

Most of the DIY photographic developers that I came across are based on adding ascorbic acid to the solution. Ascorbic acid (although not based on the benzene ring), is also a possible developer according to the Kendall-Pelz rule. This rule states that the compound can work as a developer if atoms are structured in the molecule in a certain way. However, as I am not a chemist, it is rather hard for me to explain this in more detail. Although, it is possible to mix photographic developer without adding ascorbic acid, the main advantage, as I understand, is that it helps to reduce developing times of plant-based developers. After mixing ascorbic acid with sodium carbonate the ingredient is converted into sodium ascorbate.

On the other hand, if the film or paper comes yellowish it might also be due to the fact that the ascorbic acid tinted the material.

WATER

One of the most important ingredients is water. The ideal is demineralised water, but any tap water will do.

(SODIUM SULFITE & POTASSIUM BROMIDE)

Two extra ingredients that I learnt about are sodium sulfite and potassium bromide. I have never used them before, however. Sodium sulfite is an inorganic compound which is used as a food preservative (E221). It is an oxygen scavenger. Its function is to prevent developer from oxidising and thus exhausting. Sodium sulfite is a weak alkali, and it has also mildly fixative effects.

Potassium bromide serves as a restrainer which slows down the developer and prevents the fog (prevents the unexposed silver salts from developing). However, a part of an old and used developer can be added to the newly mixed developer in order to restrain its speed and save ingredients.

VINEGAR

Stop bath is an acidic solution which is halting the alkaline developer. Instead of using conventional stop bath, we can add vinegar into the water and wash the paper/film in between developing and fixing.

FIXER

The most common fixer is Sodium or Ammonium Thiosulfate, also known as hypo. It is an inorganic compound soluble in water. During the fixing, the image is becoming permanent, the remaining unprocessed silver is dissolved in the fixer and can be reclaimed. Fixer can be reused multiple times but not endlesly. You can check if it is not exhausted by puting the strip of exposed film into the fixer, the fixer will clear the film quicker if it is fresh and slower if it is already exhausted.

SALT-FIX

Alternative to the conventional fixer can be a salt fix mixed from the high amount of the kitchen salt. However, the salt fix is rather a stabiliser not having archival qualities as conventional fixer.