There has been a lot of talk lately about the “inevitable demise” of film and the loss of the old techniques. These discussions have led to some questions regarding the long term availability of processing chemistry. What follows may be the long term answer. A number of years ago while working in a large processing facility I purchased a used Graflex Speed Graphic and in the box with the camera was a sizable number of jars and bottles filled with what are referred to as bulk chemicals. I had always been interested in chemistry and that interest was re-kindled when I saw all of the chemicals with familiar names like sodium sulfite and potassium bromide, in that box,. While in the Navy I had heard a lot of other Navy photographers talk about making their own developers from bulk chemicals and I had always been curious about this technique and my serendipitous find allowed me to explore this. In this article I will discuss how to make a developer, and a fixing bath, and what each of the individual chemicals in these solutions do during the process. We will dissect both a developer and a fixer and then discuss some of the practical aspects of making your own chemistry.
The Developer
Photographic developer at it’s most basic level is a reducing agent. What this means is it reduces a chemical compound to a less complicated chemical or even to an element. When film is exposed to the wavelengths of light to which it is sensitive, a physical change takes place to the films emulsion. The emulsion contains small “grains” called halides (salts). These halides usually are made up of Silver Bromide, Silver Iodide or Silver Chloride, there are other metal salts that are sensitive to light but the ones above tend to yield the best results and are the most practical to use in terms of their sensitivity to light and their ease of reduction in the developer. The physical change that takes place is the absorption of light energy, even in very minute amounts, by the silver salts. The more light striking the grain the more excited or activated the silver salt becomes. This overall sensitivity to light of a certain film stock is referred to as the films speed.Since developer is a reducer, the main chemical in the developer is often referred to as the reducing or developing agent. Many many developing agents are known and some are quite common. This reducing agent causes the exposed silver halides to reduce to metallic silver when the film is placed in the developing bath. The silver halides that received the most light when the camera shutter was operated reduce to the largest amounts of metallic silver, this is how density is controlled during the exposure of the film. The more “active” a developing agent is the faster it reduces these salts to silver. There are certain properties which make some developing agents more desirable than others. These properties can be anything from the ease of availability to the speed at which the developing agent reacts. Some of the more common reducing agents include; Hydroquinone, Metol also known as Elon, Phenidone, and para-phenylenediamine. I have read before that apples contain a small amount of hydroquinone in them naturally, this is why apples turn dark when cut and left in the light, and supposedly if you place a piece of film in a glass of apple juice it will eventually show a small amount of development but it would take days. In fact most developing agents used on their own work far too slowly to be practical.
Since this activity is too slow we need to speed it up. This brings us to the next chemical in the developer, the accelerator. The main purpose of the accelerator is to speed up this slow activity so we can process our film in minutes instead of days. It accomplishes this by speeding up the swelling of the gelatin base of the emulsion, thus making it more porous and thereby allowing the reducing agent to penetrate more deeply and allowing for faster processing. Without this swelling the developing agent only acts upon the silver halides close to the surface of the film. The second thing the accelerator does is absorb any halides that are liberated in the reduction process, if left in the emulsion they will create undesirable marks and effects. The most common accelerators are Borax, Sodium carbonate, sodium hydroxide and Kodak balanced alkali. Unfortunately most accelerators increase the activity too much and reduce the process times to seconds this yields unacceptable results due to the inability to precisely control the process and because of the lack of proper development response across the entire density range.
Enter the next chemical in our witches brew, the restrainer. Since the developer is now too active and only allows processing times in seconds we need a way to slow this down to a manageable level. Since no accelerator known gives exactly the right amount of development speed we need to add a restrainer. The restrainer makes the developing bath just a little more acidic. By adding a restrainer we decrease the activity of the developer, this allows for processing times in the minutes range instead of seconds, thus allowing more predictable results and it also gives better response in all densities since the developer has a longer time to work on the film. To further explain this we will look at the following characteristic curves of a piece of film. A characteristic curve is a graphical representation of a films response to exposure and development.
Curve 1 illustrates a basic characteristic curve also known as a D, log E curve where D = density and logE is the logarithm of exposure, I will not get overly technical I promise. The main parts to learn are these. There are three parts to a characteristic curve the straight line portion, which is just what it sounds like and represents the middle tones of our scene. The bottom curve and all areas to the left of it is called the toe and represents the shadows of the scene. And finally the top part of the curve and all parts to the right is known as the shoulder and represents the highlights of the scene.
The family of curves shown in curve 2 on the right can represent one of two things either A) different curves of the same type of film processed in the same developer at differing processing times and/or temperatures, or B) different curves of the same type of film processed in different developers. When film is processed for short periods of time the toe and shoulder may not receive optimal development and thus will not yield the full density of these areas of the scene. These shorter developing times straighten out the curve of our film. When we process for longer periods of time with the aid of the restrainer, somewhere over about 7 minutes, this assures that all portions of the scene receive proper development and yield accurate tonal densities. This is why many pros like to dilute their developer by 1:1 or 1:2 etc. this assures a less active developer and by compensating with longer times it allows the full tones of the scene to be rendered. The overly quick activity of the developer without a restrainer will cause chemical fog, developing streaks and low contrast since full development never takes place. The most common restrainer is potassium bromide, although other bromide solutions will work as well.
The final component to our developer is the preservative. Since all photo chemicals are water based there is always a large amount of free oxygen in solution. All organic developers in an alkaline state have a tendency to absorb large amounts of this free oxygen. This oxygen if left in the developer will oxidize a developer and render it basically useless. If we add a preservative that has a greater affinity for free oxygen than the rest of the components in the solution then it will absorb that oxygen thereby preventing oxidation, prolonging the life of the developer and eliminating stains that would be produced before the metallic silver is fully processed. There are several factors that govern just how much preservative is used in any given developer formula. The most common preservative is sodium sulfite although sodium bisulfite is also used.
Let’s breakdown a basic developer formula:
We will use DK-50 as our example.
| Water @125° F | 500ml | solvent |
| Kodak Elon | 2.5 gr | developing agent |
| Sodium sulfite | 30.0 gr | preservative |
| Hydroquinone | 2.5 gr | developing agent |
| Kodalk | 10 gr | accelerator (also known as Kodak Balanced alkali) |
| Potassium Bromide | .5 gr | restrainer |
| Cold water to make | 1litre | solvent |
I purposely chose DK-50 as my example for a number of reasons. First it has all four components, second it is a great example of an MQ type developer, third it isn’t readily available anymore and illustrates how you can make any developer you have the raw chemicals for if you have the formula, even very old formulas such as D-7 or D-23. You can even make formulas that have never been commercially available such as Beers variable contrast paper developer. The best part is you are no longer limited to the chemicals your local shop carries and you can even make other manufacturers formulas such as Agfa or Ilford. I also chose DK-50 because it is a very vesatile developer for everything from 35mm to 4×5.
A short note, one thing that often confuses many photographers is this, density is controlled by exposure but contrast is controlled by development. Once you understand this principle you will be amazed at how it will effect your picture taking and your darkroom work.
The Fixer
Once we have developed the film for the proper time we need to have a way to immediately suspend any further development and “fix” the image in a permanent state. This is the job of the fixer. After development many unexposed silver halides are still in the emulsion and are still light sensitive. If we were to turn on the lights immediately after development the unexposed halides would then be exposed to light and since there is still developer in the emulsion they will turn dark and render the image useless. The fixers job is to eliminate all of the unexposed silver salts, stop all further development and often times to shrink or “harden” the swollen emulsion.Fixing baths contain five basic ingredients and just as with the developer above I will give a brief description of each in the following few paragraphs.
Our first component in the fixer bath is the fixing agent. This agent is basically a solvent for the unexposed silver halides and it must be able to dissolve silver bromide, silver chloride and silver iodide. The most common solvent is sodium thiosulfate or as it was once commonly referred to hyposulfite or hypo. This agent reduces the silver salts to soluble silver-sodium thiosulfate compounds, it removes these compounds from the emulsion by continuously diluting and replacing them in the emulsion with fresh fixer. There are only a very limited number of substances that can accomplish this task due to the fact that a good fixer must achieve the following:
1. Dissolve the unused halides without ruining the image.
2. It must create compounds that are soluble to facilitate their removal.
3. It must not soften or continue to swell the emulsion.
Again just as with the developer we need a preservative in our solution to prolong chemical life. Since the fixer is also water based we have the same problems associated with free oxygen that we had with the developer. After development a large amount of developing agents may remain in the films emulsion. Left unchecked these developing agents will oxidize and cause stains, the preservative again absorbs this free oxygen. Another reason we need a preservative is because one of the components of the fixing bath is a strong acid and can cause the fixer to decompose and become sulfurous (hence the rotten egg smell in exhausted fixer). The preservative acts a barrier and prevents this decomposition from happening. It is imperative that the preservative be added before the acid is introduced into the formula.
Again once development ends a great deal of developing agent is left in the swollen emulsion if not neutralized development will continue and stains will be the result. Enter the Neutralizer. A neutralizer is usually an acid. By increasing the acidity of the otherwise alkaline developing agents all processing stops or is neutralized. The most commonly used neutralizer is Acetic Acid. But we must be careful to use just the right amount. Too little will not stop development, and too much will cause the fixer to sulfurize, ruin the action of the hardener and continue emulsion swelling.
Since we caused the emulsion to swell in the developer with the accelerator we need to stop and reverse this process to ensure that the emulsion will not scratch easily. The hardener, usually one of the alums and most commonly potassium alum, hardens the emulsion but leaves it expanded but firm to help in the washing of the film.
Note: if you are planning to tone a print or tint a negative do not use hardening fixer as this will close up the emulsion and your toner or tint will never penetrate.
Fixers with a hardener added have a disadvantage, they can cause excessive hypo retention in the film, to reduce this effect we must limit the range of acidity in the fixer. Over time the acidity of the bath is neutralized by films carrying over too much alkali. Eventually this decreased acidity will cause a sludge of aluminum sulfite and render the fixer unusable. If we add boric acid to the solution we can counteract this drop in acidity and because it allows the fixer to absorb a considerably larger amount of the alkali it will reduce the sludging. The boric acid is known as the anti-sludging agent
Lets breakdown a fixer formula just like we did with the developer.
We will use the Kodak formula for F-5 which is good for paper, films and plates.
Kodak F-5 hardening fixer
| Water at 125° F | 600ml | solvent |
| Sodium thiosulfate (hypo) | 240gr | Fixing agent |
| sodium sulfite | 15gr | preservative |
| 28% acetic acid | 48ml | neutralizer |
| Boric Acid | 7.5 grams | anti-sludge agent |
| Potassium alum | 15gr | hardener |
| Cold water to make | 1 liter | solvent |
A few final thoughts
In many formulas you will see chemicals marked out as anhydrous, dessicated, monohydrated, decahydrated and crystals. These terms, with the exception of crystals, refer to the amount of water in a chemical, specifically how many molecules of water there are to each molecule of chemical. Anhydrous and dessicated mean there are no molecules of water, monohydrated means one molecule of water decahydrated means it has 10 molecules of water and crystals is rather obvious. Why is this important. All chemicals have a molecular weight and our measurements are based on these weights. If I have an anhydrous compound and I leave the jar open on a humid summer day it will not take long for this compound to absorb water vapor from the air. Now instead of my compound having no water, it suddenly may become monohydrated or worse. As the amount of water in the compound increases so does it’s molecular weight. Obviously as this weight increases it will throw off the weight needed in our formulas. Fortunately the molecular weight of one molecule of water is a constant (18.01528 g/mole) and we could compensate but it is quite difficult in the home darkroom to determine the number of water molecules per compound molecule. The better solution is to simply keep your jars tightly sealed to prevent any absorptionWe have spoken of being able to create any developer or fixer you want if you have the formula and the chemicals. But where to get these formulas? Here are some resources:
The Compact Photo Lab Index, Published by Morgan and Morgan. Look for it used online or at your photo store since it no longer published. Get the newest version you can. This is the bible for photo labs. It basically has every data sheet for every film type ever made, as well as most formulas for developers, fixers, toning baths etc. and from most of the manufacturers including Polaroid, Accufine, GAF, etc. as well as the big boys.
The Darkroom Cookbook, by Stephen Anchell. This book gives many non-commercially available formulas, as well as good information on the creation and modification of these formulas.
Beyond Basic Photography, by Henry Horenstein. This book also gives some great information and some formulas that are hard to find such as the previously mentioned Beers developer.
You can obtain chemicals from Photographers Formulary in Montana. They offer more chemicals than you knew were out there as well as information on and chemicals for alternative processes such as platinum photography.
You really do not need any specialized equipment other than a good quality scale or balance. The new digital or sartorious balances available at many department stores are more than adequate for the job. Some items that will make your job easier are:
A magnetic stirrer
Large beakers
Good quality lab grade glass graduates in various sizes
Stirring rods or paddles
Good work habits and a clean environment are important to good chemical mixing to avoid contamination and improperly mixed chemistry.
Just as with mixing prepackaged chemicals it is important to not allow excess oxygen to enter the chemicals we are mixing to avoid oxidation. Never ever shake a bottle to mix it the added oxygen will reduce the effectiveness of the developer or completely ruin it. Stir slowly and do not let excess splashing occur. If you use a magnetic or paddle stirrer make sure the vortex is not letting oxygen into the mix, any sucking sound created during the mixing process means oxygen is getting in.
You can also make replenisher solutions for your developers. As you process film you simply return the developer back to it’s bottle and add the prescribed amount of replenisher for the amount of film processed. This will dramatically increase your developers working life.
To me the best part of knowing how to make your own chemistry isn’t the flexibility to make any developer or the cost savings of making only the amount you need or even the ability to create and use replenishers. To me the best part is having the knowledge of the inner workings of the developer. This knowledge allows the photographer to adjust his or her formulas to achieve different results for various situations. For example if I know that my film was accidentally overexposed by a couple of stops because I had the wrong film speed set for my meter reading I can add a 10% solution of potassium bromide to decrease the developer activity and reduce the contrast of the final product.
As with all aspects of photography you can experiment and find what works best for you. To illustrate this point when my wife and I owned a small professional lab I would keep notes on my findings one example is that I found by using Ilford Gallerie multigrade paper and Kodak Selectol developer I would get the most beautiful warm tones in the final print. These warm tones added just that little extra in my sepia toned product that one of my clients was looking for that she switched to us exclusively for all of her processing.
I hope this small introduction to making your own chemistry will inspire you to take the plunge, you will not regret it once you use this knowledge a couple of times.
Editor’s Note: The photo at the head of this article was taken by Photo.net Member Chris Waller and posted to a thread about photo chemical storage in the B&W Film & Processing forum. A topic that is actually pretty relevant to the article you just read. -Josh
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