Unlike photographs set in silver, like in black and white photography, cyanotypes are using a solution of iron compounds.
The photograph can be taken with a camera, like a digital camera, and the resulting photo turned into a negative that can be used to make a cyanotype.
The basic cyanotype recipe has not changed very much since Sir John Herschel introduced it in 1842. However, some advances have been made by Mike Ware in what is referred to as the New cyanotype process. Ware’s cyanotype formula has less bleed, shorter exposure times and a longer density range than Herschel’s, but it is also slightly more complicated to mix and uses more toxic chemicals.
The cyanotype process at a glance
The cyanotype process is simple. It can be done easily in a few steps:
The cyanotype is made up of two simple solutions.
- Potassium ferricyanide and Ferric ammonium citrate (green) are mixed with water separately.
- The two solutions are then blended together in equal parts.
Preparing the canvas
- Paper, card, textiles or any other naturally absorbent material is coated with the solution and dried in the dark.
Printing the cyanotype
- Objects or negatives are placed on the material to make a print. The cyanotype is printed using UV light, such as the sun, a light box or a UV lamp.
Processing and drying
- After exposure the material is processed by simply rinsing it in water. A white print emerges on a blue background.
- The final print is dried and admired.
In 1907, working from the research of Howard Farmer and E.J. Wall, C. Welbourne Piper publicised the working details of a process that produced an inked image from a silver bromide paper print. A non-supercoated paper print is treated in a dichromated bleach solution, converting the silver image back into silver bromide. The bleaching bath also hardens or tans the gelatine in proportion to the amount of silver present. The print is washed in water, swelling the gelatine into a relief matrix that will accept greasy ink in the shadow and mid-tone areas, but repel it in the highlights (where the water content is highest). Once the matrix has been drained and blotted, the original photographic image can be inked up with a large blunt-cut brush, or small rubber brayer. Bromoil transfer is a variant of the above wherein the inked matrix is printed onto a second sheet of paper. A mangle press or the back of a spoon can be used for the transfer, which is suitable for colour work as a series of selective matrices can be printed in register to produce a coloured image.
(in yorkshire it is known as the eeh by gum bichromate process)
Gum Bichromate is not an inherently difficult process. With practice and patience successful prints can be produced. Only one chemical is required to produce the light sensitive emulsion, and prints are developed in water. Nor is a light-tight workspace required; coating and developing can be undertaken under subdued household lighting conditions.
A word of caution is to highlight the differences between published sources of information on gum printing — perhaps due to the very flexibility that gum printing offers. There is no right way to print gum — different approaches and methods arise from the different results individual practioners seek.
The flexibility of gum means that you can choose to make graphic images in one colour, or you can seek to make three-colour images, or perhaps you prefer (as I do) to create layers of multiple colour on the one image. All these approaches are valid, however each will influence your working methods in different ways — the key is to find the working method that reflects your individual vision.
The information contained on these pages details my way of working, which has evolved from ten years working with gum. It is not the only way to print gum, but it is the way that works for me and the printmaking outcomes I desire. Your needs may be different and you should explore and investigate as much material as you need. I have suggested a variety of sites to visit and the resources section lists suggested books and other sources of information.
Gum printing variables
The skill in making gum prints is learning how to combine a variety of variables, which range from sourcing an appropriate choice of paper (or alternative support) and its preparation, through to the combination of gum and pigment, sensitiser proportion and exposure and development. These numerous variables can lead to frustration — but often the potential for prints of exquisite beauty. Patience and persistence will deliver results.
Wet Plate Collodion
This process is used to make different image types: The Ambrotype, the Tintype (also known as the Ferrotype), and a negative. In fact while the first three appear to be auto-positive images they are in fact thin negatives that via the wet plate process are able to be viewed as positives.
There are four basic sets of chemistry. The collodion (wet plate collodion process ), the Silver Bath, the Developer, and the Fixer. I will place a description of these later.
To start one needs either very clean glass, a prepared tintype sheet or black anodized aluminum plate the correct size that will fit into a plate holder.
1Pour the Collodion on
For small plate sizes (5 X 7 & down) the plate can be grasped at the lower left corner between the thumb and first finger. The collodion is poured on and then off in one smooth motion to get an even coating of the plate. There are two techniques. The first is to pour a puddle in the very center of the plate and then rock the plate to move the collodion to each corner, the second is to start pouring in the upper right corner, flow the collodion down and to the left to cover the upper left and left side of the plate and finish by flowing the bottom right corner where excess collodion is poured off. If this pouring is not done in one smooth even flow there is a great possibility that there will be ridges in your image.
2Place in silver bath
Once poured and the excess collodion is drained off of a plate and it is then placed into a silver bath. This is a solution of silver nitrate and distilled water. I have seen simple trays used but to do so one needs to remain in a completely darkroom while the plate sensitizes…about two minutes. I use a vertical bath that is light tight so that I can leave my portable darkroom (something all wet plate photographers need in the field).
3Place in plate holder
After the two minutes the plate is removed, excess silver nitrate solution that adheres to the back of the plate is wiped off by a paper towel. The sensitized plate is placed into the plate holder with the collodion side facing the lens…You did remember to make sure it is truly dark in your portable darkroom before removing the plate out of the bath and into the plate holder?
One then loads the holder onto the camera, draws the dark slide, makes the exposure and closes the dark slide. The exposure that seems to work well with new collodion is F11 or F16 at three seconds. Did I mention that the speed of the collodion changes over time? How about that you have no control over temperature? Your chemistry could be anywhere between 40 to 90 degrees F and you just have to make it work correctly. Can you do this with modern materials?
Depending on the temperature, one has from two to ten minutes to make the exposure and start development. Because once the collodion dries out on your plate, that area will not develop.
My friend John pointed out that the developer smells like apple vinegar with a bunch of nails thrown in. In fact this is about what it is. Contrary to modern photography, we want to just use the minimum amount of developer. About 14 ml for a 5 X 7. Once you have the plate out of the holder ( in the Dark room again) the correct technique is to smoothly and rapidly pour your developer onto and across the plate to completely cover it in one motion. Any place the developer stops; it will deposit a silver line that will be a streak in your image. Once the plate is covered by developer (in less that three seconds) start counting seconds in your head while watching and slowly rocking the plate. The intent is to count to 15 and to keep the developer moving. By 10 you should see a definite image. At 15 pour regular stream water over the plate. If the stream is kind of brown then be sure to get some water and let it stand overnight taking the clear stuff off the top. The water stops the development.
There are two fixing methods. One is to use Hypo or Sodium thiosulfate, the other is to use potassium cyanided. The cyanide has the added opportunity of gassing ones self if you do not completely get all the developer off the plate (cyanide gas is released by the acid). Or you could just poison yourself by having some of this material on your fingers and decide you need a sandwich. I use Hypo. The are others who use Cyanide for the image “quality”. This is a hobby for me. I do not need to risk anyone’s health close to me for a hobby.
Fixing takes as long as it takes. In most cases the rule of thumb is to watch until the image clears. The milky Iodides will be removed. Then fix for another similar length of time to completely remove the “halogens”.
As with all hypo fixed materials, the more water the better for rinsing.
Once rinsed the plates are set out to dry. Some people coat their plates with a varnish, others do not. This is poured on just as the collodion was except the varnish and plate need to be at 110 degrees F for things to work correctly. Some people also paint the collodion on ambrotypes black to protect it and to give the classical black background that these images require to become positives.
Collodion is a mixture of Ethyl Ether, Ethyl Alcohol, nitrocellulose and trace amounts of an iodide and bromide. Almost any water-soluble version of these will work. Those combined with heavier elements allow the collodion to last longer before going bad. This is months to a year. The lightest elements in combination may only be good for a month. You will need non-flexible collodion, additional Ether and Alcohol to dilute the collodion. Ether is explosive when allowed to pool / leak out of its container. It will also put you to sleep. Mix this stuff outside. I use everclear for the alcohol.
Silver nitrate crystals and distilled water. Silver nitrate will turn your skin black as well as any part of your eye it comes into contact with. Be careful or become blind.
This is usually Ferrous sulfate, acetic acid and water. I have also added Pyro from time to time.
This method of producing an image is similar to the cholorphyll process, however instead of using the leaves off a plant, you use either the petals or berries, mix with a strong alcoholic spirit, paint onto a surface, then contact print.
This method of printing a photograph is one I read about on the internet somewhere, with placing negatives on a leaf between two sheets of glass to keep it steady along with a bag of water to feed the leaf whilst development takes place.