I decided to give the new cyanotype process a try because of some frustrations I had with variations on the classic cyanotype method. The biggest problem being highlight staining, areas of deep blue bleeding into highlights fouling them. Also, emulsion run off while washing the print. A print would look good following exposure showing the "tone reversal" (formation of Prussian White in the shadows) on correct exposure, but then the wash water would take on a blue Ti-D-Bol look as the print washed away leaving an anemic result.
Mike Ware suggested I try his new method during some correspondence. I was aware of it, and had read about the process. It has gotten a reputation for being complicated, but I would beg to disagree. Replacing the ferric ammonium citrate with ferric ammonium oxalate as the sensitizer, heating the two solutions to dissolve (the second being the same potassium ferricyanide as in the original process) in a hot water bath to dissolve, combine both and let cool overnite. Filter the precipated crystals (coffee filter suffices) and top off with distilled water and (with a touch of ammonium dichromate - please use gloves and filter mask) you have a single bottle solution that has a shelf life of 4 - 5 years. Mike has complete instructions on his site.
Mike eliminated the grinding of the potassium ferricyanide long ago. He rightly points out that the materials used are more hazardous than in the classic formula - but really not much more hazardous than the chemicals used for palladium printing, and certainly a far cry from the daguerreotypists concerns.
Mike's observations on the two processes held true for me. I had some difficulty getting the sensitizer to penetrate papers with the traditional cyanotype formula. Tween 20 may have helped, but I was always left with a slightly gritty feeling on the coated surface. The new cyanotype emulsion penetrates the paper I've settled on, Crane's Weston Diploma Parchment, greedily. The addition of a drop of Tween 20 to 5ml of solution (which coats with a glass rod a 8+ inch by 28 inch sheet in 5 passes) will cause the emulsion to emerge out the other side of the paper! No Tween 20 needed. Coat smoothly and rapidly, with confidence. I did have to add a drop of 40% citric acid solution per ml of sensitizer to avoid chemical fogging by the paper.
As the (Mark Nelson designed) 31 step tablet shows to the right, cyanotype is capable of a huge tonal scale. The tablet (laid over with Pictorico Ultra Premium OHP Transparency Film which I use to prepare my digital negatives) shows 24 or 25 steps of exposure scale (each step being 1/3 stop). The tones are smooth. For all intents and purposes with the extremely smooth surface of the paper I am using this is showing smoothness and detail as if it were a fine blue palladium print.
Exposure time is speedy - using Mark Nelson's Precision Digital Negative system I calibrated a Standard Print Time of 2m 20s. I'm too old for the exposure times of classic cyanotype. Once I calibrated the process and paper I was whipping out prints like there was no tomorrow.
The sensitizer really gets into the paper and binds well (Mike explains why on his site). With classic cyanotype I had settled on an inverted wash in still water per Sam Wang's suggestion to minimize the emulsion runoff after exposure. Be gentle. Not so with the new cyanotype. Perhaps I'm getting a little crazy, but I dip it in a slightly (hydrochloric acid) acidified wash for one minute, put it inverted in clear water for a few minutes, flip it drain and run the gentle spray of a hose over the image to completely clear.
I will try the classic cyanotype process again to round out my experience with alternative processes. John Dugdale uses the traditional cyanotype process with great success. Anna Atkins algae series is sublime. But I think I'll be sticking with the new cyanotype process for my work moving forward.