The big companies use extraordinary precision in making up their chemicals. It comes from the industrial equipment and large quantities they use. Accuracy is something else. They will use only the purity of ingredients that is necessary to produce consistent results from the product they produce, and that purity will vary, sometimes within fairly large limits.
As for you, the precision you need to use depends on what you are mixing up. Fixers are not very fussy; film developers can be. There are some developers that can be compounded by the teaspoon method, however. They may not be suitable for all your needs, but they work fine for some. Dry measure may not give you the consistency you want, but that depends a lot on how consistent you are. Some people do better at it than others.
If you do buy a scale, buy a good one. That will be a fairly expensive outlay. The reason is not so much precision (although that is a considerable benefit) but ease of use, consistency over time, and long service life.
Batch size may dictate the use of a scale. Also the elimination of
variables when experimenting may call for a scale.
My Acculab with 0.01 gram resolution and accuracy covers both
of the above circumstances. Dan
If you have a scale it's probably good but if your chemistry is working fine, go with that....Evan Clarke
Among my hobbies is cooking, In the U.S., at least, recipes using flour are in cup, a volumetric measure. It's call scoop and level method. I have never in my life produced two cups that weighed the same. Nor had my average ever even been consistent. My baked good never came out right, I finally found someone who's baking was successful, had them measure four cups. I weighed that out and have used that weight for all my baking since. Now ingredients like salt and sugar are extremely consistent. Even with that said, a tsp if table salt is not the same as a tsp of kosher salt.
So, some ingredients can always be volume measured like sodium thiosulfate, if you know the equivalence. Other may prove difficult to be consistent like hydroquinone. Finally I am sure that usable results can always be obtained using the scoop method. But I would not count on consistency.
D-76 is a standard developer, although not one I use.
Ansel Adams - The Negative
Thanks, all, for your replies. Trexx, I appreciated your analogy, I like to cook as well.
I will be looking for a nice scale and know that the recipe results will be good. Some films are worth more than the convenience.
Last edited by Fred Aspen; 03-25-2009 at 12:40 PM. Click to view previous post history.
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My 2 tsp worth...
For things that do not need a lot of accuracy (or repeatability) to work well, spoon measures (or other volumetric measurements) are fine. I mix a soft-working print developer with 2-3-4 Tablespoons of Metol-sodium sulfite-sodium carbonate respectively, plus a 10ml "glug" from my 10% potassium bromide bottle regularly to use in split-developing prints. Fast, easy, no problem. Other things like fixers and MQ developers can usually be compounded with spoon measurements and still operate within acceptable parameters.
That said, weighing chemicals for more exacting formulas is the lab standard and the most accurate, so I use my scale for most things.
FWIW, I got my scale (a rather nice and very accurate one) from a police auction or cheap: seems they often have many from meth-lab busts and are happy to get rid of them. Maybe that would be a source for you?
I like to cook as well. I rarely bake, and rarely use very accurate measurements. However, it is interesting to note that here in Europe, the standard way of determining the amount of flour to use is to weigh it (in grams). Kitchen scales are standard equipment here and no one would think of baking a cake using "cups." They seem amazed that Americans can manage to bake anything... :-)
Convenience? Digital! Way ahead of a beam balance.
Originally Posted by Fred Aspen
My Acculab's capacity is 200 grams, more than enough.
A 0.01 gram accuracy and resolution is a good compromise
twixt accuracy and capacity.
A few chemicals which are long lasting in solution form
can be stored as concentrates, eg, potassium bromide
and ferricyanide. Dan
For cooking, a good measuring device is the forefinger and the tongue. There are very few photo chemicals I would do that with, even if it were practical,
Originally Posted by Doremus Scudder