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 Originally Posted by richard ide  one must (should) do everything possible to eliminate as many of the variables possible People shoot pictures with Holgas and Diana's because they don't know where the light leaks will be. They develop film in Coffee or use an unknown recipie from the internet just to see what happens. Adding uncontrolled variables is often considered a good thing.
Rather than try to do everything possible to eliminate variation I would rather say one should eliminate variables as needed - no more, no less - and that this requires a much deeper understanding of what is going on. To buy an analytical balance and weigh chemistry to the microgram takes nothing but time and money and any fool can waste both by doing so.
One begins to get a real handle on a process when one knows how much variation is acceptable. Then one can spend the time and effort concentrating on those things that really matter.
My experience testing B&W photographic materials and determining exposure requirements has shown me that the variation in the sensitive materials, agitation, temperature control, age of the developer and the water quality is much greater than any variation due to 'teaspoon measurements' when making up the developer - and that's for running film and paper through a sensitometer.
When it comes to taking pictures of real-world subjects and making prints that are subjectively pleasing - a teaspoon level of control is really more than is needed.
Volumetric measurement of dry powders is plenty Good Enough for black and white chemistry. A balance is needed, however, to calibrate the volume measurements - the 'gms/teaspoon' in the back of the darkroom cookbook is pretty approximate; powder 'density' varies with the size of the granules or crystals, and for crystals is dependent on the crystallization process. Some chemicals don't lend themselves to volume measurement - Kodak's P. Bromide that has the consistency of driveway gravel comes to mind.
Obviously, a commercial process will have a stricter level of control, as will color. But looking at the negatives that come out of the C-41 processor at Costco - flash pictures taken in Shae Stadium and the like - I'm not sure that it isn't largely wasted. I do, however, mourn for the very well run minilab at the now defunct local camera store.
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and... sheesh! guys, the OP asked a simple question....and all but one jumped on him for measuring his chems with a teaspoon. Nice. What a nice bunch of helpful folks....
That being said, what is the op doing working with chemicals without a degree in chemistry in the first place?
By the way I was using this formula even with two electronic scales. 
Amidol Teaspoon Formula
Water, 70º F
500 ml
Sodium sulfite, desicated
1 tablespoon
Amidol
1 teaspoon
Potassium bromide
1/8 teaspoon
Use full strength or 1:1. Often recommended for bromoil work.
I had to make some calculated adjustments because I use it at 68 (little circle in the upper right corner of the 8 cause my keyboard doesn't have one or a cent sign), degrees. OK I add a little more Amidol, I've got plenty on hand.
I wonder if Edward Weston used Integral Calculus to figure the volume of fixer in the depression of his raincoat were fixer was held because he didn't have a fixer tray?
Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand
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Oh rats, I just composed a long and obviously brilliant comment for this thread. Then I pushed the wrong button and lost it!
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Oh rats, I just composed a long and obviously brilliant comment for this thread. Then I pushed the wrong button and lost it!
That's OK, go ahead and redo it, we'll wait.
Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand
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Originally Posted by ntenny Though you weren't asking me, I think I've got an answer: I'd say pretty much what you're saying. The thing is, I'd have the same answer for Patrick Gainer if he asked that question.
As someone who lurks most of the time, and for whom much of the pleasure of analog is in messing around with darkroom processes, as an engineer by profession and a scientist by training, I really appreciate these discussions of process that you guys seem to have periodically. I've learned a lot from reading both of your posts, and tend to think that you're representing complementary approaches, both legitimate.
I have the impression you feel a bit ignored by the readership---a voice in the wilderness for a thorough understanding of process and tight quantitative methodology, while readers breeze past your stuff because it's difficult and run around looking for the easy answer. I can only speak for myself, but I think there are a lot of people in my position, reading your posts, thinking about them, taking things you've said into account while going about the business of turning photons into silver, but not necessarily posting about it.
Well, this is my post about it: I'm listening. Thanks.
But I still make Caffenol with volumetric measurements. :-)
-NT Thanks for the comments.
To start with, coffee is a very variable product in terms of photoactive ingredients and so making it with volumetric measurements is quite reasonable. There is a time and place for everything.
I guess there has been a history of bad science from a lab workers POV in many posts, and I have been trying to set the record straight as much as is possible. There are a lot of myths and misconceptions about mixing your own formulas, the most prevalent one being that you can get repeatable volumetric measurements. When I tried it in the lab with my 2 bottles of KBr, I got .8 - 1.2 grams of KBr for one measuring sequence, with repeats. This was worse than I had expected. So, I began this "crusade".
I'm sorry if it bothers people.
There have been a lot of posts on low quality films and papers recently. Well, this is what to expect with your developer if you use low quality measurments as well. Some companies apparently use the equivalent of kitchen chemistry to make products.
PE
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Originally Posted by Photo Engineer Now, tell me, what would you say in my place?
PE I'm not Brad, but I can answer that one. What you say, what you do, is tell the truth. A few of us will "get it" and most won't, or won't care. Such is life. You can't live other peoples' lives for them.
Remember what John Heywood wrote way back in 1546:
"A man maie well bring a horse to the water, But he can not make him drinke without he will."
Keep showing us to the water PE. Some of us are thirsty.
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Nobody knows the truth.
All prophets are false.
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The first words from the mouth of a pathological liar are "I never tell lies."
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Originally Posted by alanrockwood Oh rats, I just composed a long and obviously brilliant comment for this thread. Then I pushed the wrong button and lost it! OK, here goes again, not quite my original attempt to post, but covering some of the same issues. There are two key issues here: 1) What degree of trueness (i.e. accuracy plus precision) is required when measuring a given compound for a specific application, and 2) Is volume measurement adequate for achieving that level of trueness.
I would like to see the discussion (which pops up several times per year) focus on those two questions in a more realistic way. Let me list a few possible examples.
What degree of trueness is required for the measurement of metol for a single-component film developer? Can a volume measurement achieve it?
What degree of trueness is required for ascorbate for a two component film developer with a target concentration range for ascorbate in the saturation region with respect to superadditivity? Can a volume measurement achieve it?
What degree of trueness is required for potassium hydroxide when it is the sole activator in a developer? Can a volume measurement achieve it?
What degree if trueness is required for borax when it is the sole activator in a developer? Can a volume measurement acheive it?
What degree of trueness is required for the measurement of KBr when used in a film developer? Can a volume measurement achieve it?
What degree of trueness is required for the measurement of KBr for emulsion manufacture? Can a volume measurement achieve it?
Also, give some additional thought to the application. A print developer to be used in an amateur application with inspection-based development might not have the same requirement for trueness as a commercial film developer used in an automated film processor.
Underlying my series of questions above is the consideration of the purpose of the chemical and the sensitivity of the application to the concentration of the compound. For example the pH of a solution is more sensitive to the concentration of the activator if the solution is unbuffered (such as if potassium hydroxide is the sole activator used) than if the solution is buffered (such as if borax is used.)
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I think this is something for testing.
With volume measuring you will have a variable desity of cristals in a given volume.
So measure the weight of 10 volume samples and look how much it varies.
That variation should be taken into account to the above: is a 20% or 10% variation of each of the chemicals mentioned above noticable in the end result ?
By reasoning I think you will get more consistant results by measuring by weight than by volume, even if there are more variables into the play like the consistancy of your film/paper.
Peter
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Originally Posted by Nicholas Lindan Absolutely. And there isn't an engineer who will tell you otherwise.
If the wood block needed to be more precise then the dimensions would be specified 12.0 x 12.0 x 12.0 and any dimension from 11.9 to 12.1 would be acceptable.
If you look at an engineering drawing you will find they all specify tolerances. Usually the tolerance is implied by the number of decimal places used in the dimension. If it is a critical dimension it may be specified as, say 12.354 -0.000/+0.001 inches. Any dimension without a tolerance is suspect. What drawing? I know how to read a drawing and understand tolerance! The example given was used as given, nothing added or removed.
Would this not also apply to tablespoons? 2.0 vs. 2 tablespoons would be a large difference, would it not?
The argument that it doesn’t matter seems like an argument in favor of sloppiness.
As David Goldfarb stated, “Even setting accuracy aside, I find it easier to measure things with a scale. It's easier to scale up or down a formula with measurements in grams than trying to figure out fractions of teaspoons.”
I also think it is easier and more fool proof.
"I am one. Patrick Gainer is another." (Engineer)
Well, there are engineers and then there are engineers. The ability to communicate and be understood is more important. Stating exact specifications is a step in the right direction. Anything else leaves too much to chance.
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