DK-50 question

[robert_macdonald]

Hi,

 

I mixed up a batch of DK-50 and have two questions: What colour is it

supposed to be? There is powder that has not disolved in the bottom of

the jug (Dev. was mixed in a brown 1 gal. glass jug) and when I shake

it it turns the DK-50 into a milky colour, is this normal?

 

Thanks

 

Robert

[tklim]

Robert,

 

DK-50 is a fine developer featuring high acutance, with moderate granularity, and, in my opinion, yields negatives very similar to those devved in HC-110. I've known and used it for years. I have never experienced anything like you describe, even though now I mix my DK-50 from scratch. The formula has been revealed by Kodak and is available from many related websites.

 

You see, DK-50, an MQ formula, does not contain particularly large amounts of chemicals, e.g. only 30 g/l sodium sulphite. The accelerator used in this formula is Kodak Balanced Alkali, or Kodalk, 10 g/l. The pre-packed version probably contains also some sequestrants to prevent precipitation when used in hard water areas. The stock solution should be absolutely colourless, with possible very slight discolouration after some time (several months) of storage. All chemicals should dissolve without a trace of sediment at a moderate temperature (say, about 40C/104F). If there is a considerable amount of sediment at the bottom of the vessel, something has gone wrong. My first suspicion would fall upon the quality of water you used. Was it tap or distilled water? How old was the pack of the developer you dissolved? The actual concentrations of individual reagents in DK-50 stock solution are such that even if you don't observe the order in which they should theoretically be added, everything dissolves nicely. Another thing that has just occurred to me is that perhaps you tried to make a more concentrated solution of the dev to use it at greater dilutions. I tried that too, and even 3x normal concentration can easily be achieved, only you need to dissolve the chemicals in a specific order (i.e. metol before sulphite, etc.). Sorry I cannot help more, but there seem to be too many variables. Anyway, in the case you describe I wouldn't use the solution for developing any important films.

 

Good luck! - T.K.

[ronald_moravec1]

Advise if package mix or scratch mix. Possibilities are different.

[robert_macdonald]

Hi,

 

It was a package, mixed with tap water.

[ronald_moravec1]

1 - your heated water may have cooled from the heating vessel to the glass

 

2- the package may have been old. call kodak for replacement 800 242 2424 ex 19

 

3- sometimes a precepitate forms after some time. this is normal with some developers. decant the good stuuf off the top or filter out the precepitate or use as is

 

4- most probably all the developer did not disolve in the first place. add powder to water slowly so as to keep powder in suspension until disolved. when you think everything is in solution, shine a light thru the bottle to observe progress. when no more fine particles are circulating, stir for five more minutes intermittently

 

5-get a gallon mixing container stainless steel from Calumet and a Paterson stirrer. Heat the water on a hot plate and add powder and mix right in the stainless. Shine a light into the vessel as you mix so as to see everything is mixed. Mix at the high end of the suggested temp range.

 

6- I believe you never got all the developer into solution and the cloudiness is just circulating the undisolved powder. This batch can not be reliably fixed.

[patrick_gainer]

Minerals in tap water should not cause cloudiness in a developer using Kodalk. Borates and metaborates are used also as water softening ingredients in laundry detergents to prevent precipitation caused by other ingredients.

[robert_macdonald]

Well, the packet was old. This is probably the problem. Oh well.

 

Thanks

 

Robert