The way to buy film developer is in concentrated form. I also suggest buying it in powder form and mixing it yourself at home, but it will all depend on what kind of developer you want to try. A popular developer is Kodak’s D-76, but all developing agents are known for slightly different results. Rodinal is used for finer grain, while D-76 is more of a general use developer. Make sure that whichever developer you choose is designed for film or both film and paper, and not just paper, as darkroom sections on websites or in stores will have both.

Purchase a Chem-Seal 1 Gallon (128 oz.) Plastic Photographic Chemical Storage Container, also known as a brown plastic gallon jug in which to mix and store the developer. The idea is that the plastic is dark so that light can’t get to the chemistry. Some jugs contract with accordion ribs as the liquid is used to reduce the amount of oxygen inside too. Both light and air will eventually render the developer ineffective over time, even in ideal storage, so it’s a good idea to label your mixes with dates. Anything over 6 months old might be iffy.

But don’t worry, because developer is inexpensive. A pack of D-76 that makes a gallon of chemistry will run you about $5. Or buy in bulk, but only mix a gallon at a time.

Each pack or bottle of concetrated developer will detail the directions on how to dilute the chemistry. With the dry mix, you will have to use hot water to dissolve the powder. Running your tap water hot should be sufficiently hot. Use a digital thermometer or a meat thermometer to assess the temperature.

It’s important during the process of developing film that the developing agent be on the cool side, 68 – 70 degrees, so plan ahead. Mix your developer far enough in advance to allow it to cool down before you use it on your film.

When you use your developer mix, you will dilute it even further with room temperature water, so if you’re in a hurry, you could run your mixing water colder to compensate for the heat of the recently-mixed developer.

Next step: Preparing the Fixer