Home Brew questions.

I have read quite a few times that Gadget G. and others use the 'dry measure' method (tsp, tbsp) to quickly make home brew developers. I have tried it and it seems to work fine.

Is a scale really necessary? Do Kodak, Ilford measure hold that kind of precision in their packaged developers?

I do have a 505 grain scale for the really small quantities but I like to 'scoop' for the other ingredients. Saves time, is super convenient, but am I risking upsetting a delicate balance?

-F.

If it works for you, that's what counts. Good repeatable results are hard to beat.

Mike

I've been using the teaspoon method for years, no problems. In Anchell's "Darkroom Cookbook", there's a section provided to convert most chems from grams to teaspoons.

Fred Aspen,
It seems like your system is the best of both worlds. And, as Mike says, it's consistency and repeatability that count. BTW, I have used a scale at times and the spoon system at times and have never detected any difference.

I use a balance when I think the process I'm doing might be more sensitive to variations in weight than the probable error in the volumetric measurements. If I publish a formula with quantities expressed in weights, I actually measured those weights. I didn't start mixing my own until I came into possession of a balance. I used measuring spoons to move the substance from container to balance. After doing that a number of times, I saw that I was using the same number of spoonfuls each time, so published the article "Kitchen Tested Soups" for Petersen's Photographic. There I demonstrated by averaging multiple spoonful weights and computing the mean-square error, along with deliberate mismeasurement of quantities of critical elements of D-76 and photographic tests of the results, that the photographic tolerance was at least as great as the likely measurement error.

There have been times when I experimented on an idea using volume measurements and determined the weights for the published formula by weighing those volumes. Of course, I tested the weight formula to make sure it gave the same results.

My understanding is that the risk involved in volumetric measures lies in sample-to-sample variability of the raw ingredients. That is, there's no guarantee that a teaspon of Supplier A's metol (or whatever) will have the same mass as a teaspon of Supplier B's metol. Thus, if you start with Supplier A's metol, determine a formula that works, run out of metol and buy some from Supplier B, your formula may suddenly become radically more or less active than it was before. This issue is due in part to grain size. I myself have seen noticeable differences in grain size from two suppliers (in CD-4, IIRC) -- one supply I've got has a fine-grained, powdery consistency but another has much larger grains, almost like small pebbles. That said, I haven't bothered to check volumes and masses on these two samples, so I can't be sure the relationship differs, but I fully expect it would. The same problem can make it risky to use a formula you've found online or in a book.

That said, lots of people report good results with this method, so if you're happy with the results, you might as well keep on using it. I'd just keep an eye out for changes when you buy more of any item.

Grain size can cause weight to vary as much as +/- 10% or greater. I have done the experiment and posted the data here and on Photo Net. However, if you grind your materials to a common size powder, this would "normalize" the grains and crystals from all sources.

A mortar and pestle is best for this, but ceramic glazed or polished stone units are best, otherwise you risk cross contamination from the porous unglazed materials. A pharmacist supply probably has the glazed type.

Small variations can increase your problems from batch to batch and let your process run out of control on you unexpectedly.

PE

You do not need an expensive balance to check these questions. It needs be sensitive and repeatable, but if you have a formula for spoon measurements that works with one batch, you can measure the appropriate volume unit with the cheap or even home made balance. When you get a new batch, you can see if the same volume you weighed before weighs the same. The units of measurement may be coins, a set of buttons, thumbtacks, paper clips, etc. I wager that a dime's worth of Metol, a nickel's worth of hydroquinone, a dime's worth of borax, and 4 tablespoons of sodium sulfite in a liter or quart of water will get you a passable D-76.

gainer said:

You do not need an expensive balance to check these questions. It needs be sensitive and repeatable, but if you have a formula for spoon measurements that works with one batch, you can measure the appropriate volume unit with the cheap or even home made balance. When you get a new batch, you can see if the same volume you weighed before weighs the same. The units of measurement may be coins, a set of buttons, thumbtacks, paper clips, etc. I wager that a dime's worth of Metol, a nickel's worth of hydroquinone, a dime's worth of borax, and 4 tablespoons of sodium sulfite in a liter or quart of water will get you a passable D-76.

Click to expand...

******
And don't forget two cents worth of good, practical, advice!

Well, since this problem has not been resolved by a practical experiment I would say that there is absolutely no proof either way except for my demonstrated variations in wt vs vol between several batches of chemicals with different crystal forms.

Until that is done then we have no proof whatsoever. I think that Patrick has said it all "passable". If that is what you want, then that is what you will get! But, there is no guarantee that you will get the same result that I will if you measure as he suggests and I measure out the exact formula.

PE

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.

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.

-F.

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...

Best,

Doremus Scudder
www.DoremusScudder.com

Fred Aspen said:

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. -F.

Click to expand...

Convenience? Digital! Way ahead of a beam balance.
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

Doremus Scudder said:

My 2 tsp worth...

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...

Best,

Doremus Scudder
www.DoremusScudder.com

Click to expand...

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,