Prepare some clear leader with gelatin, by fixing unexposed film (black and white print film or other film with a clear base) , or by bleaching a finished black and white print with R-9 bleach or equivalent. Note that peroxide – acetic acid bleach seems to have trouble clearing existing prints, and unfortunately (given it’s toxicity) R-9 works better. For best results, either clear or re-soak previously cleared leader 12 – 24 hours before using it for this cyanotype process. It will absorb the cyanotype solution better if it is recently dried. Make sure it’s dry before going on!
You could also coat your own gelatin onto clear leader, and use that. Specific instructions for this are beyond the scope of this recipe!
Make up solutions A and B below. Distilled water is preferred, but the process seems pretty tolerant of tap water.
water, @~20°C 100ml
Ferric Ammonium Citrate 25g
water, @~20°C 100ml
Potassium Ferricyanide 10g
Cyanotype solution is not (very) light sensitive when wet, and can be coated in normal room light. It’s best to avoid bright sunlight when coating. Once it is dry, it becomes light sensitive, so plan accordingly!
When ready to coat, mix together equal volumes solutions A and B. The general idea is to immerse the clear film in it and leave it for a few minutes, long enough that the gelatin soaks up the cyanotype solution.
Since the resulting cyanotype film is much too slow for a camera and thus is to be contact printed in some way or other, you probably don’t need to make a long camera roll. It is easier to soak if you cut it into strips of a good length for contact printing before you soak it. I find about four feet (1.3m) to be a good length.
If you are soaking pre-cut strips, pour the mixture of solutions A and B into a small photographic print processing tray or 2.5 gallon bucket or any other container in which the volume of cyanotype solution makes a depth of at least one film width. Soak one strip of film at a time, making sure that each strip gets thoroughly submerged for a minute or two.
If you are coating a longer roll of film and have a Lomo tank, you can load the clear film onto the spiral and fill the tank with cyanotype solution. If you are not using enough volume of cyanotype solution to submerge the film, shake it gently for several minutes to make sure it all gets coated.
If you don’t have a Lomo tank, unroll the film and cram it into a Mason jar big enough to hold it all. Pour in the cyanotype solution, put the lid on, and shake it gently for a few minutes. You should probably shake it often and let it soak longer, since it won’t all be submerged at once.
When finished soaking, save the cyanotype solution in a container that either is dark or that has a dark place you can store it and use it again. It won’t last months, but probably weeks and certainly days.
Whatever method you use to soak it, pull the strips or roll out of the solution and hang it above a surface that you don’t mind staining blue — sheets of newspaper if inside, or the ground if you have an outdoor clothesline.
Hang it somewhere that is or can be made dark for as long as the drying will take (which depends on temperature, air flow, and humidity) and until you can come put the film into a dark box.
If you hang it outdoors, make sure that it is actually dark and that you are sure that, one, it will dry before dawn, and, two, you will not fail to retrieve it before dawn! I rather like drying outdoors, as I tend to spend time in places that actually are dark at night, but it definitely requires a commitment not to oversleep!
Once the film is dry it is light sensitive, but mostly to UV light. Thus, you can do the pre-exposure layout in normal room light, or outdoors in the hard shadow of a house or tree.
You can then contact print using either a portable board which you lay out inside or in the shade, and then bring out into the sun or expose to a uv lamp, or lay the film out onto what would be a sunny surface that you shade for as long as it takes to do the layout work, and then remove the shade for exposure. See the Orocyanogram Expedition for an example of this.
In either case, lay whatever objects or “negatives” you’d like to print on top of it.
Expose outdoors in full sun for 5 to 30 minutes. Ten minutes is a good place to start. You want to overexpose a bit, as the “development” will tend to make the image thinner.
Prepare two water baths, each deep enough to submerge the length of film you’re exposing. Put the baths where you want to do the development, ideally in a shady spot if you’re outdoors.
Remove the exposed film to a dimmer indoor light or shade and remove the objects or negative. Immerse the film in the first water bath (hereafter known as the “Dirty” bath), for 3 minutes. Most of the yellow Ferricyanide in the unexposed areas will wash out here. You can keep this dirty bath for future use when you do this process again; it will collect all the most potentially harmful waste that you don’t want to put down the drain.
Move it to the second bath (the “clean” bath). Let it soak until all the yellow washes out. Depending on temperature, this should take somewhere between 3 and 15 minutes more.
Once the film is thus “developed,” you can take the optional step of putting it in a bath of 0.3% Hydrogen Peroxide (that is, the Hydrogen Peroxide you can buy at the Drug or Grocery store, diluted 1:9 in water). This will make the blue immediately darker, raising the contrast and improving the image. The Hydrogen Peroxide accelerates the oxidation of the Prussian Blue that forms the image that exposure to air would do eventually without it.
Dispose of the “dirty” bath as you would hosuehold hazardous waste. It’s not actually very toxic, but it’s best not to put it down the drain. The “clean” water bath can be disposed of down the drain.
This is the simplest historical process. For further investigation, Mike Ware’s website takes it much further: