PMK Working Solution Color Change

[Steve Hamley]

I was getting low on PMK stock, which had acted exactly like Gordon Hutchings described when mixed (distilled water, for stock and working solutions), turning grey-green then to a medium amber color.

However, the last batch I mixed up (April), in full amber glass bottles for "A", the working solution doesn't go through the grey-green color transition, not a trace. The activity seems about right as does the stain color. The one neg I've processed with the new solution seems possibly a bit lower in contrast, although not by a tremendous amount. In other words, it seems to mix up like WD2D, not PMK.

I've been using the "B" stock with the old "A" stock with color change, so I'm reasonably certain "B"isn't it.

Toss it? Ignore it and keep going? Suggestions? Advice?

Cheers, Steve

 

[Mike Wilde]

How new was the pyro powder you used to make the A?

I keep my pyrogallol powder in a small glass jar with its tight fitting lid screwed on snugly, and the whole affair is kept in the freezer. Same thing for the Glycin. Some developers oxidize on their own more quickly than others.

 

[Steve Hamley]

Hi Mike,

It was the same pyro as the older stock, and it was white and not visually discolored.

Cheers, Steve

 

[Robert Hall]

Ignore it.

Mine used to change as described, but since I have used the newer Pyro powder, they change a little differently.

I have used 3 gallons of part A and countless parts B and with no ill effect.

It still lasts for years in a half full container.

 

[Steve Hamley]

Thanks Robert,

That's what I hoped to hear.

Cheers, Steve

 

[brucemuir]

I use the liquid concentrate kit from PF and it is at least 5 years old.

I haven't monitored the color change but it does wind up amber and seems to work fine. I also don't ALWAYS use distilled water to make my working solution.

I'll run a roll tonight and see if I get the grey/green intermediate color but I always figured if it was amber you were good?

 

[Steve Hamley]

Thanks Bruce,

That would be great. The reason for the post is on page 15 of "The Book of Pyro" by Gordon Hutchings:

"Note: When the PMK working solution is mixed together, it will immediately proceed through color changes from gray-green to pale amber. This is an important check of solution activity. If there is no color change, something is wrong!"

So naturally since I'd been seeing the gray-green to amber (more like peach, a little more reddish than amber) transition, I was curious to know if it meant something when there was suddenly no gray green.

Cheers, Steve

 

[brucemuir]

Steve,
I don't have the book but in the mixing instructions from PF for the liquid kit it does warn:Note:
"When PMK is mixed together, the solution will immediately proceed
through color changes from gray-green to pale amber. This is an important visual
check of solution activity. If there is no color change, something is wrong.
Recheck your stock solution for correct formulation. Use immediately."

It's funny because when I first read this post I thought about it and said to myself...

hmm lately I don't recall noticing a gray greenish intermediate chance like I vaguely remember when the kit was new.
I could be imagining this but

I do have a roll of 120 triX ready to process but was waiting to run 2 rolls at once.

I'll go ahead and run it and report back.

I've always had excellent results with this kit with a variety of films but I don't have a densitometer to compare exact contrast range.

Edit:
Okay, negs are drying and look good
I mixed
10ml A
20ml B
slight darkish green turning to amber/ice tea color
added distilled water to 1000ml and the color is now the tint of weak tea or a slight amberish color

trix 120 @ 250
24c for 12 minutes

upon dumping the spent/oxidized PMK there now is a distinct gray/green/black color

I use no PMK afterbath and used TF4 and straight tap water for my stop

Stain with TrIX 120 is an obvious greenish/gray
hope this helps