Sanity Check Please . . . regarding Developer Ratios

removed account4 · Mar 26, 2018

Alessandro Serrao said:
The other 2% have studied chemistry and work in labs...

i asked someone who stiudied chemistry and has a chemistry degree.
he also said there is another way to express 1:1 >>> 1/2 : 1/2

can you find reference to the notation you are talking about ?
i'd like to forward it to the chemist i spoke with and ask him about it.

thanks

Bill Burk · Mar 26, 2018

Last time we had this discussion I looked through the oldest reference books I had. Kodak always explained in words what the notation meant.

The older books listed the name of the chemical next to the amount of that chemical.

Though I do wonder about how to make a 10% solution of potassium bromide. Mallinckrodt says 1 ounce of potassium bromide to... whatever it takes to make 10 ounces total. Wonder why they didn’t just say 1:10 or 1+9

Sal Santamaura · Mar 26, 2018

Alessandro Serrao said:
What u are missing is that me and Ian Grant have perfectly clear how diluitions work, even in a photographic context...Kodak wrote 1:3, incorrectly...

I'm not missing anything. I completely comprehend how chemists notate dilutions. It was explained to me very clearly in the multiple chemistry courses and laboratories that were part of my college engineering curriculum.

Kodak didn't write anything "incorrectly." It decided to communicate differently than chemists do. It established documentation for its products that was designed for conveying to photographers how they should dilute developers. Being the dominant manufacturer for a century, Kodak's method of conveying developer dilution became the dominant method. Your and Ian's attempts to "correct" Kodak at this point are doomed to failure and create even more confusion than already exists. Chemical purity is a good thing. Chemical notation purity isn't always a good thing. Its value depends on context. Last time I checked, PHOTRIO wasn't a Web site for chemists.

Bill Burk · Mar 26, 2018

Sal Santamaura said:
Kodak didn't write anything "incorrectly." It decided to communicate differently than chemists do. It established documentation for its products that was designed for conveying to photographers how they should dilute developers. Being the dominant manufacturer for a century, Kodak's method of conveying developer dilution became the dominant method. Your and Ian's attempts to "correct" Kodak at this point are doomed to failure...

I like the summary, and think it’s pretty funny the conclusion.

You state the obvious... it’s too late to rewrite what’s been written.

Bill Burk · Mar 26, 2018

And a note to Ian Grant, whenever you finish your lost labor of love, I’ll be first in line for a copy. I’ll figure out the proportions somehow.

Sirius Glass · Mar 26, 2018

Sal Santamaura said:
I suspect you missed Billy's sarcastic intent.

I most surely did.

Sirius Glass · Mar 26, 2018

jnanian said:
so, i talked to a classically trained chemist
he told me 1:1 is one part something mixed into 1 part something

Yep

darkroommike · Mar 26, 2018

Bill Burk said:
Last time we had this discussion I looked through the oldest reference books I had. Kodak always explained in words what the notation meant.

The older books listed the name of the chemical next to the amount of that chemical.

Though I do wonder about how to make a 10% solution of potassium bromide. Mallinckrodt says 1 ounce of potassium bromide to... whatever it takes to make 10 ounces total. Wonder why they didn’t just say 1:10 or 1+9

Normal photographer percentage solutions are made on a weight of chemical to a total volume. So to make a 10% potassium bromide solution you take 10 grams KBr and dilute it it about 80mL of water and them add water to make 100mL when the KBr is totally dissolved. It's a little trickier in the English system since weights are usually in grains and liquid fluid ounce for volume measurements. Chemists usually use Normal or Molar solutions or sometimes w/w dilutions of other things for their fussier requirements.

I just got a copy of the Mallinckrodt manual but cannot find it right now. Photographic Facts and Formulas by Wall and Jordan says a 1% solution is 4.8 grains dissolved to make 1 liquid ounce, and 10% would be 48 grains to make one ounce so to make 10 ounces you would put 480.0 grains to make 10 ounces of solution. A liquid ounce is 480 minims, and...

sweet Jehosaphat aren't you glad we now use the metric system!!!!

Doremus Scudder · Mar 27, 2018

1:2 magnification... Is that one part image to two parts subject? How about ppm? Is 5 ppm 5+999,995 or 5+1,000,000 ? How about my map? Is one centimeter to one hundred meters 1:10,000 or 1:.... gee, whatever??

Sorry, couldn't resist

Vaughn · Mar 27, 2018

Hike!

AgX · Mar 27, 2018

CMoore said:
.....then what does this mean.?
....1:1
What is your math for this.?

I find this the really tricky one!!

With the common rule (followed by me too), of 1:3 meaning 1 of 3 parts total, or 33%,

1:1 would mean 100%

But in this case I really doubt the editor meant this...

In German we got the expression of "1 against X" which means a ratio, EXCEPT for "1 against 1", which means 1+1.
But only with reference to mixtures. With scale "1 against 1" still means 100%

Exception to the rule??

AgX · Mar 27, 2018

The confusion in this thread, but also a recent discussion about the location of sheet-film notches, shows how important exact wording is.

In this case, where fixed phrases turned out to be ambigious, we should strive to give additional information.

for instance:

" make a mixture of 1:3 = 1part + 2parts"

removed account4 · Mar 27, 2018

sprint chemistry's website ( read " how to mix " )
http://sprintsystems.com/products/standard-film-developer/

pentaxuser · Mar 27, 2018

I note the thread's title and can only hope that John Galt has in fact retained his sanity

pentaxuser

AgX · Mar 27, 2018

Maybe... but the rest of is confused...

Sanity Check Please . . . regarding Developer Ratios

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