PMK Pyro Developer:
PMK is a modern developer based on Pyrogallol, a developing agent that was popular in the late 19th and early 20th centuries.
It is unique because it imparts a greenish-brown stain to the image that is proportional to the amount of exposure. So, highlight areas stain more than shadow areas. The stain makes up part of the image density, so it provides smoother gradation and better separation of values than an image made up of just silver.
The downside is that there is a speed loss of about a stop with most films, and the developer is finicky to work with. It requires a different agitation method than most developers, and it is more toxic.
I've been using it extensively for Ilford FP-4 and Ilford HP5, because of its unique tonal rendering, which gives an image that looks like you could almost reach into it. Worth the effort, but not really a good developer to learn with because of its quirks. It also works well with Ilford Pan-F, Kodak Tmax 100 and Tmax 400, and Fuji Acros 100.
Using PMK:
PMK can be purchased in kits with the powdered chemicals that you have to dissolve in water, or it can be purchased in liquid form. I strongly recommend the liquid, due to the very high toxicity of Pyrogallol. If you inhale any of the powder, it can make you very sick. I use the liquid kit from Photographers Formulary.
There are two concentrates used for PMK. Part A contains the developing agents, and Part B is a saturated solution of Sodium Metaborate. Part B lasts forever in storage, but Part A does go bad if exposed to light. It is said to have a shelf life of many years, though I have never had a bottle last more than a year without it losing strength. Storing it in the dark will lengthen the storage life of the concentrate.
PMK is used in a highly diluted form for the working strength solution. The standard dilution is one Part A + two Parts B + 100 parts water (1+2+100). You should use distilled water for mixing all photographic chemicals, but it is especially important for PMK, as it is very sensitive to variations in water quality.
To make one liter of working strength PMK, start with one liter of distilled water, then add 10ml of Part A. Next add 20ml of Part B. Make sure to shake the part B bottle before use, as the chemicals can settle in the bottle. Once both chemicals have been added, stir it until it stops changing color. You will see it suddenly darken, then get lighter and turn a pale brown color.
I have a video showing how to mix and use PMK on YouTube, which shows the color change that happens during mixing. It is the only photo chemical I have used that does this, and kind of makes me feel like a mad scientist!
Prerinse
If you find you're getting spots or streaks on your film, a water pre-soak often eliminates the problem. I have had it happen most often with 120 film, rather than 35mm, and I now pre-soak all of my 120 film I develop in PMK.
To pre-soak, use plain water the same temperature that you're going to use for your developer and pour it in the tank. Agitate for one minute, then you can let it sit while you prepare the developer. When you're ready to develop, pour out the water and put in the developer. Add 20 seconds to your developing time if you do the pre-soak.
Agitation with PMK:
Note that PMK requires different agitation than what is outlined at the top of the page for other developers! Agitation must be constant for the first minute, then two inversions every 15 seconds for the rest of the developing time.
Fixer for PMK:
According to Gordon Hutchings, the formulator of PMK, film developed in PMK should be fixed in an alkaline fixer, rather than the standard acidic fixers we normally use. The stain formed as part of the image by pyro developers is inhibited by acidic conditions, so an alkaline fixer is supposed to allow maximum pyro stain effect. I use Photographers Formulary TF-4 alkaline rapid fixer, which can be purchased directly from Photographers Formulary or from suppliers like Freestyle and B&H. Fixing times are the same as for other rapid fixers.
