adjustments to Pyrocat HD formula

[sanking]

Sandy claims that "on the whole the preparation of percentage solutions is both easy and simple." Well, it only is when you know which set of units you are using.


Kirk

No point to belabor the obvious, *but* if one is mixing photograhic chemicals and knows the reference literature one already knows that the sets used are w/v and v/v. And this is not just Kodak literature, but virtually every reference text on the mixing of photograhic chemicals out there.

Your message of yesterday failed to recognize and/or state that very simple and important fact, and in failing to do so it caused some confusion, IMHO.

Sandy

[Kirk Keyes]

No point to belabor the obvious, *but* if one is mixing photograhic chemicals and knows the reference literature one already knows that the sets used are w/v and v/v.

Sure, obvious to some - but not everyone knows the reference literature.

And a lot of times people just toss out percent solutions so you can't be certain they are all using the same units.

Kind of like when you said, "This would be a 100% solution of Stock B" when referring to the way the formulary was originally giving instructions for making the Pyrocat. Even to people with some experience with making solutions a 100% solution will be puzzling - as many people may intuitively expect a 100% solution to only contain one material, instead of two.

I have no disagreement that it is not really 100%, I'm just proposing that it be noted as 100% w/v. For clarity sake.

[Ole]

No point to belabor the obvious, *but* if one is mixing photograhic chemicals and knows the reference literature one already knows that the sets used are w/v and v/v. And this is not just Kodak literature, but virtually every reference text on the mixing of photograhic chemicals out there.

Your message of yesterday failed to recognize and/or state that very simple and important fact, and in failing to do so it caused some confusion, IMHO.

Sandy

If one knows the reference literature one will know that the percentaces stated are probably either w/v, w/w, or v/v. Very large parts of the reference provide no means of knowing which is intended. Some recipes would give supersaturated solutions in some combinations, which might even possibly be correct.

"Virtually every reference text" out there is at best vague, at worst misleading. I'm not talking about the original patents, only that information available to an average user with less than a doctorate in photographic chemistry.

[Gim]

I will make this one of these days and have no problem with "adding 100 grams of potassium carbonate to 100 ml of water" as the directions say. I'm glad I'm not any smarter so as to not make mountains out of molehills.
jim