Talbotype Process Notes
By Dan Estabrook | Published
The Calotype Process According to William Henry Fox Talbot (N.B.: These procedural notes are adapted from those of Richard Morris, who kindly shared his knowledge with me many years ago. His account was subsequently included in John Barnier's excellent book Coming Into Focus (San Francisco: Chronicle Books, 2000)) • Overview: The Calotype, created by William Henry Fox Talbot in the fall of 1840, was the first paper negative process fast enough to challenge the Daguerreotype in speed and utility. As an improvement on Talbot's earlier Photogenic Drawings, the Calotype can be made with a shorter exposure, and the latent image is developed-out, rather than printed-out by exposure alone. Talbot patented his Calotype process in 1841, unfortunately inhibiting its widespread adoption – except in Scotland, where the patent did not hold, and in France, where it was completely ignored. Those who did have success with the process quickly came up with a wide variety of alterations and advancements, but the basic chemistry of the process remains the same. There are chiefly four chemicals involved at the heart of the Calotype process and its successors: Potassium Iodide, Silver Nitrate, Gallic Acid and Acetic Acid. Much like in Photogenic Drawing (but even more like the Daguerreotype), a light-sensitive silver halide is created by combining the Silver Nitrate and the salt, in this case Potassium Iodide. Gallic Acid is the main developer, and Acetic Acid is used as a restrainer. The trick to a successful Calotype is in finding a balance between sensitivity and stability, and even in the 1840's this was not an easy task. What's more, since the chemistry is embedded within the fibers of the paper substrate (without the pre-waxing and other treatments of later inventions) there are a multitude of other unwanted problems that can arise. Talbot's process seems to hinge on striking an almost unstable equilibrium of these elements – sensitizing, exposing wet and developing quickly before it fails. Even he had his difficulties at the time, so patience and a celebration of failure are perhaps required even to begin. • Paper: Before one even mixes the chemistry, there is the paper base to deal with. Contemporary papers are quite different from 19th-century ones, and most of them simply will not work with the process at all. Even Talbot had his favorite (Whatman Turkey Mill from 1840), and the hunt for the ideal paper seems to consume a good deal of a contemporary Calotypist's time. At the very least, your paper should be thin but strong enough to withstand a lot of washing; it should be free of watermarks, which would print through to your positive; and it should be relatively consistent in texture, without interfering in printing the image. Many "acid-free" papers sold today contain alkaline buffers that are deadly to the process, but you should also avoid papers that contain wood lignins or other impurities. As of Spring 2012, two modern and widely-available papers that work well are Clearprint Design Vellum 1000H, and Canson Marker Pro Layout. Each is relatively thin and chemically stable, although the Clearprint has a more noticeable texture throughout that can be distracting. There are vellums, too, that some have had success with, including Canson Vidalon Vellum, but I find them less dimensionally stable and so a bit more difficult to work with. There may be other rag resumé papers that work, and when they do they are my favorite to use, but the whims of large manufacturers can change how a paper is made from time to time, and even just a little is enough to ruin its use for Calotypy. (This happened with my old favorite paper, Crane's Crest Wove, although every now and then I find a batch that works.) A simple pre-wash in vinegar can be enough to remove the buffering from some papers, making them suitable for use, but it's an extra step that doesn't always yield favorable results. • Iodizing: The first step in preparing the paper is to create a layer of Silver Iodide on the negative surface. In Talbot's method, this chemistry is done in two stages: 1. Brush the surface with a 7.5% solution of Silver Nitrate As with all difficult photographic chemistry, it is wise to use only distilled water for each part. This pre-silvering stage should be done in subdued light or under a darkroom safelight. Tape your paper to a clean work surface and clearly mark which side will be iodized. I prefer to draw out in pencil the full size of my image, leaving plenty of border around each side so that I do not allow chemistry to get over the edges and on the back of my paper. Brush an even coating of Silver Nitrate on the top surface and let it become matte-dry, just until it loses its shine. A soft hake brush is best, preferably without any metal near the bristles. (Alternately, you could float the paper on a bath of silver, or use a coating rod, as you prefer, although these can create other problems: it is easy to get silver on the back of floated papers, and thin paper can buckle under the rod.) The paper should be quite even in surface, without pools or spots of silver, but do not let it become too dry. 2. Soak the paper for 2-3 minutes in a bath of 5.6% Potassium Iodide I prefer to do this one sheet at a time, to make sure it is well submerged in the bath, allowing an even layer of Silver Iodide to form on the surface. Agitate lightly while you wait, and make sure there are no bubbles on the surface or below the paper. 3. Wash the iodized paper in running water for two hours Yep, two hours… Make sure your wash is truly changing the water, like a print washer would, but much more gently. It is best to have several papers washing at once, so they don't move around too much and tear or crimp. It is also wise to shuffle the sheets gently every fifteen minutes or so. You may notice a slight purple stain from iodine in the paper, but don't worry. I use this as an indicator, and when it's gone, the paper is ready (generally in two hours, depending on the flow of water.) The surface of your paper will be a pale yellow. 4. Hang to air-dry Your iodized paper is light-safe, and will keep well if stored safely. • Shooting & Processing: Before you begin shooting, you must prepare the chemistry for sensitizing and developing. (It'd be a good idea to mix your fixer too.) 5. Mix the Aceto-Nitrate of Silver Mix 11.4g of Silver Nitrate into 100ml of distilled water. To this add 19.4ml of Glacial Acetic Acid. This solution will keep if stored well in a small brown bottle. It helps to use a bottle with an eyedropper built into the cap. 6. Mix a saturated solution of Gallic Acid Gallic Acid oxidizes pretty quickly, so it's best to mix this just before use. A saturated solution is about 0.8% at 68°F. I don't use much in a typical shooting session, so instead of risking the small measurements I make my saturated solution by mixing in more Gallic Acid powder than can be dissolved in distilled water and filtering out the excess. Talbot's original formula called for sensitizing the paper with a mixture of the above two solutions, further diluted with a quantity of water, depending on the desired sensitivity of the paper. Only later did he admit that a sensitizer that included Gallic Acid made the solution very unstable and prone to "embrowning" the negative. In practice, it is better to use just the Aceto-Nitrate of Silver, adding a drop or two of Gallic for speed only if you're feeling very brave or lucky. Once your camera is set up and you're ready to shoot, tape your iodized paper to your darkroom work surface. 7. Mix your working sensitizer just before use by adding 4 drops of Aceto-Nitrate of Silver to 4ml of distilled water 8. Brush the sensitizer onto the surface of the paper Once again, you will be brushing this only onto the iodized surface, and letting it become matte dry. It is very important to note that the brush you use here cannot be used more than once without contaminating later negatives. Therefore a disposable brush, such as a buckle brush, is necessary for sensitizing and developing. I simply use a cotton ball in my (gloved) fingers at each step. It's fine for anything up to 8" x 10". You may also wish to float, or rod-coat here. 9. Load your camera back Once the paper has lost its shine, but is still moist, it can be fit into your film or plate holder and put into the camera. Be careful to keep the paper as flat as possible, and to protect the surface from the dark slide. There are many ways to do this, of course, depending on the type of holder you use. I sandwich my paper in a mylar sleeve, which can be fit into a film back, or a wet-plate back (with a piece of glass behind it to protect from the spring.) Many Calotypists prefer to sandwich the paper between two sheets of glass, but you must account for the altered focal plane. Each of these methods helps keep the paper moist for the duration of the exposure. 10. Shoot Daylight is, of course, best. Try one minute at f 5.6 in bright sun. As soon as your exposure is done bring the holder back into the darkroom, and tape your paper down again. It should still be relatively moist. 11. Mix your developing solution by adding equal parts of Aceto-Nitrate of Silver and Gallic Acid 2ml of each should be plenty to cover an 8"x 10" if using a buckle brush or cotton balls. 12. Develop the negative Carefully brush the solution across the surface of the negative, making sure not to leave any blank streaks or spots. Do not rub the surface too hard. The image should start to appear almost immediately. Let it sit until the highlights develop quite dense, and subtle shadow details begin to appear. While it is only the Gallic Acid that is absolutely necessary for developing the silver image (through chemical development) the addition of the Aceto-Nitrate of Silver enhances density by selectively redepositing silver on the image (by physical development.) For greatest density, you may want a second pass of this first developing solution. A few minutes for each pass will suffice. 13. Brush off excess developer with distilled water This step helps stop the physical development and remove excess free silver from the surface, resulting in a cleaner image. A couple of passes with clean cotton balls dipped in distilled water should do the trick 14. Finish development with straight Gallic Acid Brush across the negative as above. Without this final developing step, you can lose density in the image as it fixes. Wait a minute or two to reach full development. 15. Rinse A distilled water rinse is safest, but a regular tap-water wash for about a minute will work fine. You want to remove the acids from the surface, as well as any free silver halides. 16. Fix in a standard 10% Sodium Thiosulfate Bath As with salt prints, you may get less bleaching if the fixing bath is slightly alkaline. Add 0.2% Sodium Carbonate. Fix until no trace of yellow iodide stain is left in the paper. You will probably have to inspect the negative by backlight to see for sure if it is gone. If not, the stain will show as a density change on your print. 17. Wash, gently and thoroughly You may use a simple Sodium Sulfite washing aid if you wish, but it is not necessary. 18. Hang to dry, and admire • Finishing Calotype negatives are often waxed for transparency, in order to make them easier to print with better contrast. This also stiffens and protects the paper, while removing some of the texture. Negatives done on Vellum or other transparent papers can be printed without waxing. There are a variety of ways to wax a negative, the most commonly described being to shave small pieces of beeswax over the negative and then iron it lightly between sheets of blotter paper. Several of my students have preferred to dip the negative in a warmed tray of liquid wax and then blot off the excess. Another more controlled (if slightly more tedious) method is to use a hairdryer or low-set heatgun to melt wax directly into the paper. • Notes There are many small variables to this finicky process, any one of which can make it nearly impossible to get a good negative. Problems usually show up as fogging, and Paper is almost always the culprit. When in doubt, remix your chemistry from scratch, making sure to use clean beakers and distilled water. Try developing a recently iodized (but un-sensitized) sheet of paper. If any tone or fog develops, it is not well iodized and will be useless in camera. If it is fogging during exposure, you may want to increase the amount of Acetic Acid restrainer in your sensitizer, or use only 2-3 drops of silver. You may lose effective speed, but you will get a clearer negative. Of course, when the process works well, you will get a dense and detailed negative in a very neutral black and white. It will print beautifully in Salt, Albumen or any long-tonal-range process.