Developing Film

All photos and text © 2002 - 2004 Glenn E. Stewart. All rights reserved.

This page last modified 18 Aug., 2004

from: Stumbling around in the Dark(room)

by Glenn Stewart

Over last four months I've introduced you to darkroom work and given you a pretty complete list of the tools and hardware you'll needed to work in the darkroom. Now it's time to get down to business. This month we'll tackle developing your first roll of black and white film.

Let's start by discussing the film. Black and white film has several components. The plastic "film" is called the base. It holds all the other parts together. The second major component is called the emulsion. The emulsion is made of several parts. There is the gelatin, some stuff that chemists call silver "salts" (silver halides), and sometimes one or more filtering layers. Finally, there is the anti-halation layer. The anti-halation layer lies between the base and the emulsion. It prevents light from passing through the emulsion, then either reflecting back through the emulsion or being piped sideways by the fiber optic qualities of the plastic base. This keeps your image sharp by preventing the stray light from exposing the emulsion to the sides of where the light passed through, which would appear as a halo or a fuzzy edge.

The emulsion is the light sensitive part of the film. It consists of a gelatin material in which is embedded silver compounds like silver bromide, silver iodide, silver chloride or some combination of these silver halides. On a microscopic scale, the gelatin is like a sponge. When it gets wet, it swells and gets soft. It is very easy to scratch the emulsion when it is wet, so handle the wet film with great care during processing. The swelling of the emulsion is what allows the developing chemicals to penetrate and come into contact with all the silver halide crystals that are embedded in the emulsion. The gelatin is made from animal bones. Kind of a yucky concept, but hey, what else do you do with a bunch of animal bones after the butcher gets done with them? The animal rights crowd may now want to switch to digital. You can adopt the slogan: “Digital doesn’t moo”. Go ahead. I relinquish all claims to the copyright.

The filtering layer is used to modify the film's response to certain colors. All films are highly sensitive to blue light, probably because it has the most energy. They are far less sensitive to red. This is something I will discuss in a later column, so keep it in mind. A filtering layer is sometimes used to help balance the color sensitivity of the film so the blue things in the scene don’t get overexposed while the red things get underexposed.

The first chemical used in the film development process is the developer. When you shoot a photo, you are allowing light to strike the photosensitive part (the emulsion) of the film. The light energy makes a chemical change in the silver halides within the emulsion. At this point, the change is not visible. The image is hidden, and is often called a "latent" (hidden) image. This latent, or hidden, image is revealed by the developer. The magic in the development process is that the developer acts on the silver halides to change the parts that were struck by light into metallic silver. The silver halides in the parts of the emulsion that were not struck by light are not converted and remain in their original chemical state as halides.

The second chemical used is the stop bath. This is a very mild acid that neutralizes the developer. Don't be scared by the term "acid". Vinegar and lemon juice both contain acids. The sour taste in vinegar and lemon juice is due to the acetic and citric acid they contain. In fact, stop bath is actually diluted vinegar (in a more pure chemical form). Though vinegar's active ingredient is acetic acid, it contains a lot of water and some additional natural chemicals that modify its taste slightly. Stop bath is simply made up of water and acetic acid without the taste-modifying chemicals. Stop bath is used to immediately arrest the action of the developer so we can control the extent of the development.

The fixer is a chemical that will dissolve silver halides but will not dissolve metallic silver (OK, it will dissolve silver, but at a much slower rate than it will dissolve the silver halides). Fixing the film removes the unexposed, and thus undeveloped, silver halides from the parts of the emulsion that were not hit by light, while leaving behind the metallic silver that was created by the developer when it acted upon the exposed silver halides. When the fixing process is complete, there is nothing left in the film emulsion but the metallic silver. This is the dark material that makes up the negative photographic image.

At this point, while the film is completely developed, it still contains some fixer, which must be washed out to prevent deterioration of the film. Most people simply wash the film in water to remove the fixer. This works very well and is inexpensive. Some people use a wash agent, often called hypo-clearing agent, to speed the process. There are a number of good reasons to use a wash agent with some films and print papers, but it is not a necessity with most b&w materials. Hypo clearing agent, itself, does not complete the washing process. The film must still be washed in water to remove the hypo-clearing agent. Water will do a complete job of washing the film without the hypo-clearing agent in most cases without any additional expense or storage hassle, it just takes longer.

Finally the film must be dried. Select an area where the air is still and dust-free. Attach a film clip or spring-type clothes pin to each end of the film and hang it to dry. The clip on the bottom is important to keep the film from curling as it dries. As the water evaporates the emulsion shrinks. Since the film base does not contain water, it doesn’t dry out. With one side of the film shrinking and the other side staying the same length, curling is the natural result if you don’t hang a weight of some kind on the bottom end of the film as it dries.

Arizona water is very hard and can leave some nasty spots on your film, like your dishwasher does on glassware if you don't use a sheeting agent. There are a number of ways to eliminate drying spots. Some people use Kodak Photo-Flo. It's economical and easy to use. Some others use either distilled water as a final rinse, or use it for spraying the hanging film to displace the tap water. Others use distilled water mixed with isopropyl alcohol to speed drying. I prefer the Photo-Flo.

As I said in a previous article, I also use a sponge-faced squeegee to remove most of the water before I hang the film to dry. To prevent scratching, I use the following method: The squeegee is kept as clean as I can possibly keep it. Before each use I hold the sponges under running water and rub the surfaces thoroughly with my thumb to wash away any tiny particles of dirt or dust that may have gotten on them. I squeeze out most of the water and then place the squeegee in a container of Photo-Flo that’s mixed and ready for use on the film. It remains there while the film soaks in Photo-Flo after the wash step. Just before I take the film out of the tank I remove the squeegee from the container and squeeze out as much of the Photo-Flo as I can. I remove the film from the tank and developing reel and attach the top film clip. I then run the squeegee down the film using very light pressure so the sponges can absorb the excess Photo-Flo from both sides of the film. The pressure is only as much as is required to keep the sponges in contact with the full width of the film. When I reach the bottom, I lay the squeegee down across the top of the Photo-Flo container so it won’t get dirty, then I attach the lower film clip. After hanging the film to dry I again thoroughly wash the squeegee sponges under running water, squeeze out the excess and place the squeegee somewhere clean so it can dry. I haven’t scratched a film in 30 years using this method.

Now that you understand what happens to the film during the development process, let's follow the process step-by-step.

The first step toward developing your film is to mix the chemicals. This is pretty straightforward. Follow the directions on the chemical package. Though some people like to use distilled water to mix the developer, this is not required. Any drinkable tap water will work. There are two secrets I’ll let you in on. 1.) Try not to mix too much air with the developer. In other words, don’t mix it too vigorously. The oxygen in the air that gets mixed in during vigorous stirring deteriorates the developer. 2.) Use HOT water. The developer and fixer need hot water to dissolve, unless you have a spare day or so to spend mixing them in cool water. I usually mix my chemicals immediately before I use them, so they’re too hot to use at the moment all the chemicals are dissolved. I solve this problem by using less water than is recommended for mixing, then when all the powder is dissolved, I add ice cubes to bring the water volume up to the required level and to simultaneously cool the mixture.

I use Kodak D-76 developer, which comes in a powder form. Many people use powdered Kodak Fixer (watch these two fixer names carefully), because it is very inexpensive. D-76 dissolves pretty easily, but Kodak Fixer is a real pain. I quit using it many years ago and switched to Kodafix. Kodafix comes in liquid form, so mixing it is as simple as adding the proper ratios of Kodafix and water and stirring gently for a few seconds. Stop bath and Photo-Flo are just as simple to mix, since they, too, come in liquid form.

Once you have your chemicals mixed and stored in properly labeled bottles and cooled to the recommended temperature, you’re ready to start. To avoid using the chemicals out of sequence, I recommend that you set the bottles on your work surface in the order you will be using them. I work from left to right, but you can work from right to left if you want to. Whichever direction you choose, make it an unbreakable habit. We’ll assume that your film is already loaded in the developing tank. Select the proper development time from the chart that came with the film, matching the time with the measured temperature of the developer, or get the development time from another reliable source (see film mfr’s web site). Pour the developer in quickly through the hole in the top of the tank and start the timer when the tank is full. Rap the bottom of the tank FIRMLY on the work surface several times to dislodge any air bubbles that may have been trapped between the reel and the film as you poured in the developer (hang onto the lid while rapping the tank). Omitting this step will leave undeveloped spots on the film. The rapping of the tank is why I believe stainless tanks are a better choice than plastic. Eventually, the plastic will break, but the stainless won’t. When the development period is complete, you’ll pour the used developer out through the hole in the top of the tank. I hope I’m not getting carried away by stating the obvious, but DON’T TAKE THE LID OFF THE TANK UNTIL THE FIXER STEP IS COMPLETED. All chemistry (developer, stop bath and fixer) enters and exits the tank through the light trap hole in the tank lid. Be sure you hold the lid on the tank while it’s inverted for emptying.

During development, the developer that is in contact with the most strongly exposed parts of the film becomes worn out fairly quickly. In order to promote even development, the film must be agitated so the worn out developer gets replaced with fresh developer from the volume of chemical in the tank. This can be accomplished in a couple of ways, depending on the type of developing tank you use. Follow the tank manufacturer's instructions for proper agitation. My tanks are designed for inversion agitation. The recommended agitation cycle is continuous agitation for the first 30 seconds, a 25 second rest, followed by 5 inversions of the tank in 5 seconds, then another 25 seconds rest. The 5/25 cycle then repeats for the remainder of the development period. Be sure to start pouring out the developer early enough that you can start pouring in the stop bath at exactly the end of the development period. You can determine this time by practicing with a tank full of water before developing your first roll of film.

Development stops almost instantly when the stop bath contacts the film. I usually agitate the stop bath for 15 seconds and let it rest for an additional 15 seconds. The length of the stop bath step is not critical. 30 seconds is quite sufficient for a minimum, but no harm will come by letting the film sit in the stop bath for too long. I don’t even know what too long would be for stop bath. When the developer is neutralized, the stop bath has done its job. After that it just kinda sits there.

The fixer must be agitated in the same manner as the developer. 30/25/5/25/5, etc. until the fixing time is complete. If you’re using Kodak T-Max films you may need to fix for a longer time than you do for other films, such as Kodak Tri-X. The T-Max film chemistry is different from conventional films and it just needs a little more time in the fixer. If you're using T-Max and your film looks a little pink after it's been fixed, another minute or so of fixing will help, but the pink filtering dye may also be removed by additional washing. It’s important to be sure the film is completely fixed. Kodak recommends that you fix for twice the length of time it takes for the film to clear. To test this, cut off a short section of unused film (the leader from a roll of 35mm is a good test vehicle) and place it in a clear container filled with fixer. Agitate it occasionally and time how long it takes for the film to become clear. Double this value and you have your fix time. When fixing is complete you can take the lid off the tank,

When I was in college back in the 60’s my chemistry prof taught me a method for quickly washing my film. A year or so ago I finally found the same method on the Kodak web site. It works well and saves water. Kodak has always said that film should be washed for 30 minutes in running water. It’s not necessary. Run water into the open tank deep enough to cover the film reel. Swish it around for a few seconds, then pour it out.  Repeat this process 10 times (Kodak) or 15 times (Stew). My 30-year-old negatives look as good as new, so I know I haven’t left any residual fixer in the film. This method saves about 20 minutes and a LOT of water. It has also been 100 percent effective in removing the pink tinge that is often seen in T-Max film.

When the wash step is complete, use the Photo-Flo per the instructions and then hang the film to dry. Once the film is dry, it can be cut into strips and stored in archival negative storage pages in a 3-ring binder.

So there are your developing steps: Developer, Stop Bath, Fixer, Wash, Photo-Flo and hang-to-dry. Total time is about a half hour.

People often want to know what the best method is for determining how long to develop subsequent rolls of film in developer that’s been used. My answer is: Don’t. I use my chemicals in a one-shot system. After each chemical has been used once I throw it out. “But,” they say, “isn’t that a really expensive way to work? I mean, can’t you develop several dozen rolls of 35mm in a gallon of D-76?” Well, you can, but if you don’t guess correctly at the development times as the chemical becomes depleted, how does it affect your negatives? How important is it to you that your negatives have consistent contrast and density? Do you want to adjust your printing times from roll-to-roll, or would you like some consistency in your results? One of the best decisions I ever made was to stop being a skinflint about the cost of developing chemicals. As soon as I started using them one-shot, my negatives became absolutely consistent and printing times became predictable. The time and printing paper I save not having to adjust print contrast and print time from roll to roll is worth far more than the cost of the chemicals. Just what is the cost of working one-shot? I’ve computed the following using Kodak D-76, Kodak Indicator Stop Bath and Kodafix (certainly not the cheapest trio you can use). I buy D-76 in half-gallon sizes, which is not the most economical way, but it results in the most efficient use for my purposes. I use my D-76 mixed 1:1 (working strength developer mixed per mfrs instructions:additional water), so I get twice as many rolls/half gallon as I would using the developer at full working strength. This also lengthens my development time and makes it easier to control development. Considering the small amount of stop bath that’s required and the cost of the Kodafix, the overall cost per roll of 120 film (equivalent to a 36 exposure roll of 35mm) comes out to about 75 cents. This is considerably less than it would cost to have someone else develop the film, and I know exactly what I will be gettting. I know how much contrast my negs will have, I know they're properly fixed and properly washed. In addition, for my 75 cents I get absolute consistency. I think it’s a small price to pay for the excellent results I get. For me, one-shot is the way to go.

Next month I’ll start discussing printmaking.

Remember, questions will be answered if you'll send them to me.

Best regards,

Stew

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