ArticleslgStudy

chemistry

Photographic fixer

Photographic fixer is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Photographic fixer rather than just read about it. In short: Photographic fixer is a chemical, or mixture of chemicals, used as the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed light-sensitive material from the media, and making it insensitive to further action by light.

Photographic fixer — main illustration
Photographic fixer — illustration

Key takeaways

  • Photographic fixer belongs to chemistry; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Photographic fixer to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Photographic fixer from memory before moving on to harder problems.

Reference excerpt

Photographic fixer is a chemical, or mixture of chemicals, used as the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed light-sensitive material from the media, and making it insensitive to further action by light. In the gelatin silver process, the basis for all film photography, exposed silver halides are reduced to metallic silver by the developer, forming the image. Once development is complete, remaining silver halides are removed from the film or photographic paper by the fixer, typically sodium or ammonium thiosulfate. Without fixing, the remaining silver halide would darken and cause fogging of the image.

Chemistry Fixation is commonly achieved by treating the film or paper with a solution of thiosulfate salt. Popular salts are sodium thiosulfate—commonly called hypo—and ammonium thiosulfate—commonly used in modern rapid fixer formulae. Fixation by thiosulfate involves these chemical reactions (X = halide, typically Br−):

AgX + 2 S2O32− → [Ag(S2O3)2]3− + X− AgX + 3 S2O32− → [Ag(S2O3)3]5− + X− In addition to thiosulphate the fixer typically contains mildly acidic compounds to adjust the pH and suppress trace amounts of the developer. This compound is often an alkali hydrogen sulfite (bisulfite) which also serves to preserve the thiosulphate. Less commonly it may also contain other additives e.g. for the hardening of gelatin. There are also non-thiosulphate fixers, at least for special purposes. Fixer is used for processing all commonly used films, including black-and-white films, Kodachrome, and chromogenic films.

Chromogenic films In chromogenic films, the remaining silver must be removed by a chemical mixture called a bleach fix, sometimes shortened to blix. This mixture contains ammonium thiosulfate and ferric EDTA, a powerful chelating agent. The fixing agent reduces the silver which is then dissolved by the chelating agent.

Washing and stabilisation After fixation, washing is important to remove the exhausted chemicals from the emulsion. Otherwise they cause image deterioration. Other treatments of the remaining silver-based image are sometimes used to prevent "burning".

References

Illustrations

Photographic fixer: A black and white photographic print in a tray while being processed after exposure to light under a photographic enlarger. Typically three trays are used containing either developer, stop bath, or fixer, in that order. The print must then be rinsed in water to remove the fixer.
A black and white photographic print in a tray while being processed after exposure to light under a photographic enlarger. Typically three trays are used containing either developer, stop bath, or fixer, in that order. The print must then be rinsed in water to remove the fixer.

Worked examples

Example 1 — a first encounter with Photographic fixer

Start with the simplest possible case. Write down what Photographic fixer claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Photographic fixer before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Photographic fixer ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Photographic fixer

In research
Photographic fixer appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Photographic fixer in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Photographic fixer is common in secondary-school and first-year university syllabi. It links to neighbouring topics Filmmaking stubs, Photographic chemicals, Photographic processes, so understanding it makes those chapters shorter.
In everyday life
Look for Photographic fixer outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Photographic fixer in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Photographic fixer means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Photographic fixer out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Photographic fixer in simple terms?

Photographic fixer is a chemical, or mixture of chemicals, used as the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed light-sensitive material from the media, and making it insensitive to further action by light.

Why does Photographic fixer matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Photographic fixer?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Photographic fixer.

Tags

  • Filmmaking stubs
  • Photographic chemicals
  • Photographic processes

Keep exploring