Salt

Salt Fix

Photographic fixer is a chemical that is used to stabilise black and white photographs. If we do not fix our images, they will continue to change colour and darken. By fixing, the film or paper becomes insensitive to further action by light.

Traditional fixer uses a solution of thiosulfate salt, preservatives and other additives which can be damaging to the environment. Further to this, it removes the unexposed silver, dissolving it into the solution. These Silver ions are very toxic to microorganisms and can be detrimental to our soils and marine organisms.

It is tricky to properly and safely dispose of used photographic fixer because of this potential harm to microbes and plants. The silver needs to be fully reclaimed and removed from the solution before steps are taken to degrade the chemistry. 

A low-toxicity photographic fixer, that does not dissolve much of the silver ions, can be made from just salt and water. The solution needs to be as salty as possible. Working with a salt- based fixer, means that we can lessen some of these environmental concerns.

Making process

Recipe for making salt fix with sea water:

This makes enough fixer to cover a 35mm film or to use in a small tray for prints. It does not become used up or exhausted and can be reused forever.

1. Collect a bucket of seawater. Try to collect it from a deeper section of the water, to avoid picking up sand or algae.

2. Filter the water through a fine sieve to remove any debris or sand.

3. Place the water in a shallow dish or pan and put it on top of a heat source to allow the water to evaporate. Think about how you can use minimal energy to do this. For example, in warmer weather, you can leave seawater out to evaporate from the sun over days or weeks. In the winter, if you have a fire going, you can place the dish over the fire to evaporate. If using a direct heat source such as a fire, as the water evaporates, keep topping it up with more seawater.
- You will need roughly 10-15 litres of water to make a 300ml solution with 100g of salt content, which is maximum salinity (saltiness).

4. Once you see salt grains or crystals begin to form at the bottom or around the edges of the dish, your solution should be at maximum salinity. At this stage, remove the dish from the heat and allow the solution to cool to roughly 35ºC.

5. Use this salt solution as a photographic fixer for films or prints. Use it under red light for paper and no light for film.

6. Leave in the solution for 48 hours for film or resin-coated paper and 72 hours for fibre-based paper with occasional agitation.

7. After 48/72 hours, rinse the film or paper and take it out into the light. Look carefully for any colour changes. If you notice areas turning darker, purple or pink tones, then heat the salt solution back up to a maximum of 35ºC and put the film or paper back into the salt fixer for an additional 2 hours.

Text submitted by the maker and edited by the Future Materials Bank. For information about reproducing (a part of) this text, please contact the maker.