Mixing working solution math question

[markrewald]

I posted this question on Flickr, but my lack of patience got the better of me.

My experience has been with single developer solutions (i.e. D-76 and Rodinal) so the math seems pretty easy to me. For instance, if I want to make 800ml of a working solution of D-76 at a 1+1 ration it is 400ml of D-76 to 400ml of water.

Now I want to try PMK Pyro. Mixing as I see it is: 1 part A + 2 part B + 100 parts water. So do I divide 800ml by 103 (1+2+100) to find the individual parts? So in this example it would be: 9.7ml part A + 19.5ml part B + 770.8ml of water?

Sorry if this is a noob question.

 

[DLawson]

I posted this question on Flickr, but my lack of patience got the better of me.

My experience has been with single developer solutions (i.e. D-76 and Rodinal) so the math seems pretty easy to me. For instance, if I want to make 800ml of a working solution of D-76 at a 1+1 ration it is 400ml of D-76 to 400ml of water.

Now I want to try PMK Pyro. Mixing as I see it is: 1 part A + 2 part B + 100 parts water. So do I divide 800ml by 103 (1+2+100) to find the individual parts? So in this example it would be: 9.7ml part A + 19.5ml part B + 770.8ml of water?

Sorry if this is a noob question.

The recommendation I have seen is to just mix up 824ml and not sweat the small overage.

But if you are good at measuring to 0.1ml, you can do that too.

 

[Ian Grant]

D76 1+1 is fine

In practice with Pyrocat, PMK. Rodinal etc most users use 1+1 made up to a 100, it's more about being consistent. The point is trying to measure 9.7ml is not easy, I've worked that way for 40 years. You can't measure the larger volume accurately enough to be pedantic.

Ian

 

[bdial]

You have the math right, it's your desired total volume divided by the total number of parts. But as DLawson points out, for the high dilution formulas, most people just make a convienient round off and call it good enough.
It is good enough, as long as you are consistent with whatever method you choose, for whatever chem you are working with.

 

[Joe Mace]

I posted this question on Flickr, but my lack of patience got the better of me.

My experience has been with single developer solutions (i.e. D-76 and Rodinal) so the math seems pretty easy to me. For instance, if I want to make 800ml of a working solution of D-76 at a 1+1 ration it is 400ml of D-76 to 400ml of water.

Now I want to try PMK Pyro. Mixing as I see it is: 1 part A + 2 part B + 100 parts water. So do I divide 800ml by 103 (1+2+100) to find the individual parts? So in this example it would be: 9.7ml part A + 19.5ml part B + 770.8ml of water?

Sorry if this is a noob question.

I may be wrong, but I've been under the impression that 1:2:100 (for example) means 1mL of Part A, 2mL of Part B, and 100mL of water. So this example would yield 103mL of developer. (The units of measure don't matter, as long as they're all the same.)

For your volume, I'd use 8mL part A, 16mL part B, and 800mL of water.

My research into Pyrocat on unblinkingeye.com led to my interpretation of how these ratios are used. I sure hope I'm not wrong. I'm going to start my inaugural use of Pyrocat-MC this coming weekend.

Joe