Wednesday, 27 June 2012

Making up PMK Pyro from Raw.

This is the first time I've mixed a developer from scratch. I find when  preparing for something that is new, it seems to take an inordinately long time to set up. This has been no different and I can understand why more people do not mix for themselves.
Before you start.
If you have just purchased new scales it is a good idea to check how accurate they are. First thing to do is place the scales where you plan to make up the mix and zero them.The table that follows is a simple and affective way of checking the accuracy.

These weights came from the royal mint:

Coin test
        ●         1p – 3.56 grams.
         2p – 7.12 grams.
         5p – 3.25 grams.
         10p – 6.5 grams.
         20p – 3.0 grams.
         50p – 8.0 grams.
         £1 – 9.5 grams.
         £2 – 12 grams.

An alternative to using scales is the Twenty P mix. This is where twenty p coins are used as a counter balance to weighing out the powders. While talking about alternative ways of measuring out you can use measuring spoons. This could be a more reliable way of ensuring that each mix is consistent. If you measure out the chemicals with number of spoons it will not matter that the powders have changed in volume by absorbing moisture or drying out.

With the checks out of the way what next? How much are you going to make up as stock solution? I know from previous use that it will keep for a very long time, even years. I personally prefer only to have small amounts of developer on the shelf ready for use. This is partly because I use several different film and paper developers.  Anchells Darkroom Cookbook  suggests that you make up part A at 750 mls and part B at 1400 mls; well that is a large amount for a first mix not only that what happens if you get it wrong  or heaven forbid it does not work. Luckily Trevor Crone has published the weights for a smaller amount:

Solution A to make 250mls:
         Metol 2.5 grams
         Sodium metabisulphite 5.0 grams.
         Pyrogallol 25.0 grams.

Solution B to make 500mls

         Sodium Metaborate 125 grams.
Stock solution should be made up with distilled/de ionised water. EDTA-disodium is an optional ingredient It adds gold tone to the silver of the film.

Trevor suggests a reduction of 10 grams for solution B to help combat separation when mixed. He has also said that to his knowledge it has not affected the quality of his negatives.  I can confirm the drop out is reduced but I think this is mainly due to the reduction of powder. Although these quantities are more reasonable  I made my batch up at half these weights.

Other bits
Paper cup cake holders are a good idea for pouring the powders into when it comes to measuring out but they will only cope safely with small weights. You can get plastic cups to do the job which maybe a better route to take if you plan to mix all your own chemicals.

Common sense should prevail when it comes to measuring out these powders. Gloves and a breathing mask should be the minimum safety precautions taken. If the powder gets air born it will irritate the lining of your nose. Also if you get it on your hands it  will irritate or burn your skin. So please be sensible.  

Adox CHS 100 Pet ISO 100 35mm flim.
Developed in PMK Pyro,
Printed on silverproof paper,
Developed in Ilford warm tone.
Having purchased all the ingredients to mix it myself, is it more cost affective? The over the counter premixed price of PMK is about £9 for 10 litres. The cost of all the ingredients is around £39. The batch that I made up  was equivalent to ten litres and saved about 50p. Taking every thing into account scales, time, safety etc. etc., it may not be worth all the trouble and money as a one off. There are advantages to this method such as the flexibility of making up the quantities of developer, stop and fix you require and being able to try out other developers you would not normal be able to get from the mainstream. The main purpose for me was to ensure a ready supply of PMK Pyro. Now that I have started down this road as my stop,fix and other developers run out they will probably be replaced with powdered formulas.

Acknowledgements and Thanks to the following:

Paul C, for the royal mint weights. 
Mr S. Nichols for the 20 P mix.
Trevor Crone for the reduced PMK Pyro mix.