Welcome to Chemistry Connections, our names are Riya Mishra and Summer Wang and we are your hosts for episode #12 called the Chemistry Behind Film Development. Today we will be discussing what makes film cameras, such as Polaroids, or Canon Cameras, work.
In this episode, we’re going to be talking about how film is developed, and the chemical processes which occur every step of the way. Thanks to inventor and scientist Edwin H. Land, people can enjoy the look of a film picture without having to go through the process of developing film. Picture dark room photography, the low lights, the chemicals, and the long-long process before you get your photos. Now imagine that condensed into a tiny camera, weeks of work can be completed in a minute. This popular camera, made by popular companies like Polaroid and Instax provides a physical, and tangible memento in an instant. It seems like magic… but it’s all chemistry.
Segment 2: The Chemistry Behind Film Cameras
When you hit ‘click’ on your camera, how does the photographic film develop on an atomic level? Firstly, it’s important to know that film is covered in a crystalline solid, usually a silver halide (so silver and a halogen). The most popular choice for film is silver bromide (AgBr). When photons from light come into contact with one of the grains, an electron is ejected from the valence levels of the bromine atoms, and onto the conduction band of the crystal. Then, the electron combines with a moving silver ion, and makes atomic silver. When this occurs multiple times, a clump of silver metal is produced. That atomic silver creates dark areas on the paper due to its color. The colorless ion Ag+ gains an electron to form solid silver. This seemingly simple reaction creates the dark colors that you see in your pictures. The formation of silver metal is directly proportional to the intensity of light. This may sound confusing, but it means that more light hitting the film means that area will appear darker when the film is developed. So, if anyone ever tells you to keep your picture in the dark as it develops, you know why.
For non-instant film cameras, once the picture is taken, film must be placed in a developer, or a chemical liquid which makes the concealed image on the film eventually visible. Developer itself can be chemically altered to adjust the rate at which the film develops-mainly with the usage of developing agents. Without developing agents, the process of film development could take hours, or even days! But, with some developing agents, like potassium hydroxide (KOH), this process can be sped up. You see, for film to develop at the quickest rate possible, the developing solution should have a pH between 10-11. This is a pretty high pH, meaning there needs to be a way for film developers to reach that pH without interfering with other parts of the developing process. KOH happens to be an extremely strong alkali, or a strong base. When KOH is added to the film, it produces an alkaline solution on top of the film. This raises the pH, bringing it to that 10-11 pH range which is optimal for development. So, by raising the pH, the entire process is sped up, and chemistry saves us tons of time!
What interested you in this topic? Why is it important? Anything else you’d like to share.
So, why did we choose this topic?
For me, I love movies, and I knew I wanted to research a topic related to filmmaking in some way. I loved learning about the most basic tool for creating a movie, a camera, and really understanding the ways it works on a chemical level. I’ve also always been fascinated by the film development that goes into the creation of older movies and pictures. These chemical processes have been used by filmmakers and photographers for hundreds of years, and it’s interesting to think that the basics of chemistry we’ve learned in school can explain the creation of such beautiful movies or photos.
For me, I felt interested in this topic due to my love for art. Photography is such an interesting and special form of art, and I knew I wanted to learn more about how it works. Also, I’m the kind of person who loves capturing different moments with my friends on my Polaroid, and it was nice to learn about an object that’s given me a physical reminder of some of my favorite memories. Getting to know what really happens when I hit that button on the top of the camera is super interesting!
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