The Film Developing Cookbook

Measuring Spoons are *not* a replacement

I don't recommend measuring spoons as a replacement for a scale.

Here's why:

When you are measuring powder the amount of mass per unit volume is referred to as the "bulk density". This entity is usually quite different than the regular notion of "density" which referes to the amount of mass per unit volume if the material is in a single piece.

The big problem with "bulk density" is that it can vary enormously (granules of the powder can be different sizes) from one measuring session to the next and the amount that the powder is "packed" in the measuring container (i.e. a measuring spoon) varies as well. I have been told it is very hard to accurately measure amounts within 15-20% of the target amount with any consistency using the measuring spoon method.

And wait, it gets worse ...

There are several chemicals that are found in needle-like crystals. For these substances it is almost impossible to get within 50% of the target amount with any consistency. To make matters even worse, substances that fall into this category are those where extreme accuracy if required to obtain good amounts (e.g. BZT - you don't want to go overboard on this stuff!).

On occasion, some have mentioned that some chemicals that are hygroscopic are best measured using volumetric means because they absorb moisture from the air and the amount weighed on the scale will be inaccurate. That would be true - if one repeatedly opened the container of contents to withdraw amounts of the material. The way around this is to simply buy small amounts of the material (yes - it's more expensive this way) and mix the entire contents in solution at once. Mercifully, there are relatively few substances that fall into this category.

I used to use the measuring spoon method. Due to the problems cited (and verified by my own personal experience) I no longer do so and my results are the better for it.

I have two accurate balances. I can weigh small amounts to the grain and large amounts to the 1/10 gram. I wrote an article in 1973 called "Kitchen Tested Soups" in which I measured ten teaspoons each of various chemicals, weighing each and getting averages and standard deviations. The standard deveiations were no more than 1/10 gram. Next I mixed up D-76 using accurately weighed amounts and different teaspoon formulas varying the amounts of metol, hydroquinone and borax by 1/4 teaspoon in a planned experiment to see how much tolerance there might be for differences between measurements by weight and by volume. If you look closely in "The Darkroom Cookbook" you will see a number of formulas for developers similar to D-76 that differ by greater amounts than you would expect from using teaspoons. I will never convince you who doubt me, but that is not my aim in life. If I can give someone a simple and consistent formula that does not need a balance, let alone one that weighs to the milligram, the balance can come later.

I concluded that for the developers I tested, the use of volume measurements would not affect the consistency of the results. I would not recommend it for quantitative analysis or basic research, but with proper precautions, it works fine.

You suggest using stock solutions of certain hygroscopic chemicals. The same concept can be and is applied to complete developers. Take your supposed and in some cases that I have tested, imaginary, errors and divide them by 50 or 100 to see how fine a balance you would need to measure out the chemicals for a single batch of working solution of some of the developers we use.

peters said:

Arigram-you'd do better to get yourself a copy of the Photo-Lab iindex. Most of the info in the darkroom cookbook was taken directly from that journal.

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Thanks for that I nearly bit for a copy of the Darkroom cookbook today on Ebay.

Just remembered thanks to your post that I bought the Photo-Lab index a few years ago, I'll go and dig it out

while spoons are not very good measn to measure phenidone or sub-gram compounds, they work fine for sulfuite, carbonate, vitamin C, etc.

Yet, when in need they can be used.

Thanks for the response, and I am aware of your position on the matter from the Ascorbate Developers article on the unblinkingeye.com site. I don't wholly disagree with it - but I have some particular concerns of my own.

In essence, I think there's a happy place between the imprecision of volumetric measurements and splurging 200+ USD for a balance that is accurate to 0.1 mg. I'd like to think I've found a home in that place, so here goes:

Agreed - there are many close relatives of D-76 that can be "accidentally" produced by introducing the measuring errors associated with volumetric measures of chemicals - and yet give perfrectly agreeable results. Even so, when I wish to produce a batch D-76 I'd like the finished result to be just that - not Ansco 17 which it is perfectly possible to produce unintenitionally through measurement errors. As I focus on the 35 mm format (at least for now) these inconsistencies might be, occasionally, sufficient to show up in an 7X enlargement.

Regarding the expenditure for a balance - it is perfectly possible to acquire one for $40 USD (Lyamn Pro Series) that is going to be accurate to within about 5 mg or so. This is perfrectly acceptable accuracy for me and dramatically better than I get with my $3, $7, or $9 measuring spoons.

And on the topic of measuring spoons - an experiment I performed a few weeks back suggested that both the accuracy of the smaller sized spoons is flawed; a completely separate concern from the bulk density matter. My experiment was very simple and consisted of filling the 1/16 tsp spoon with water and decanting it into a small graduate. I repeated this action 16 times and then attempted to decant the graduate into the 1 tsp spoon. I performed this experiment 3 times with each of my 3 mixing spoon sets, and I found that each set produced between 1/8 and 1/4 tsp MORE than the expected 1 tsp of liquid. Admittedly, surface tension could play a bit of a role here as I'm measuring out a liquid - but I consciously tried to avoid over-filling the spoon. This particular issue only appears to pose a concern for the smallest of spoon volumes (e.g. 1/16 tsp) - but since I'm often concerned with these amounts for restrainers - where an error can leave me with higher base fog (a royal P.I.T.A. for my paritcular paper and light source combo.) or degraded sharpness, contrast, and film speed, I consider the $40 to be well spent.

Regarding your last point - I do try to avoid working in very small amounts. When a formula calls for something like 1% BZT I'll try mixing a couple liters of the solution to minimize the loss of accuracy introduced by the smaller amount comforted in the fact that it will likely keep for some time. Where Phenidone is concerned I try to avoid mixing formulas that call for less than 0.5 g. And in any case, I'm a heck of a lot more comfortable weighing this out on a balance accurate to 5 mg (1%) vs. the perhaps 50 mg inaccuracy introduced by the spoon. Fortunately, your own PC-TEA formula has allowed me to circumvent this matter entirely, as I now produce 1 L of PC-TEA stock which contains a much easier to amount of 2.5g. I've also had the good fortune to avoid having to use hygroscopic chemicals, such as Sodium Carbonate or Sodium Hydroxide, for my mixing activities.

My personal belief is that if one really doesn't have the means to procure an adequate balance - which shouldn't really be cost prohibitive or very complex to use - and one has only volumetric measuring means at his/her disposal, I think it would be best to consider restricting one's mixing activities to producing Rodinal, PC-TEA or similar formulas that are highly-concentrated, have long shelf-life, and are therefore likely to offer the maker some guarantee of consistent (if not optimal) results.

On the other hand, if one is going to be producing a batch of only 1 liter of D-23 or D-76H stock using volumetric means - it's going to be difficult to achieve consistency from batch to batch.

I am amazed - $600 to $2300 for a decent lens and $40 for a balance. Repeatability gives the confidence in technique to free one up from the wonderment of "will it work?" A decent scale has a load cell. Good load cells cost from $50 to $500 ea. Then there is the electronics. If you want to split the range of the load cell into 30,000 accurate divisions with maybe a million internal counts of resolution with compensation for linearity and filtering - I would think that about $600 would be a good figure. I would say that for a scale with both good electronics and a good linear load cell, a minimum of $750 would be in order. Now- calibration .... did you know that the spin of the earth causes gravity to be a little different at each latitude. (something about centrifigal force) Enough to make a plane crash from overloading - as plane weighers require you state your latitude. That means something calibrated in China will likely not be correct in LA. That means you need calibration weights. Oh - yeah -calibration weights cost more that 40 - a lot more! Good thing you can measure these chemicals with a spoon and still make them work. .... well ... at least some of them. If I didn't have the bucks to buy a decent electronic scale, I would at least get a good triple beam balance. Maybe one that has been gone through. They can do an excellent job for about $100 or so.

OK - I am done ranting now .... just hit a soft spot is all. Sometimes lowest bidder mentality doesn't make the world a better place is all.

aldevo said:

On the other hand, if one is going to be producing a batch of only 1 liter of D-23 or D-76H stock using volumetric means - it's going to be difficult to achieve consistency from batch to batch.

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My viewpoint is that there are two things we should know here. How accurately can I measure, and how accurately must I measure in order to get the results I want. I do not like to feel anxious about something unless I know it's something that warrants anxiety. I have seen formulas that were obviously converted from avoirdupois to metric, and the converter didn't know when to stop the significant figures. Some of my old friends, when they read my article, went out and spent much coin of the realm on analytical balances so they could weigh these ridiculously precisely specified weights. Well, it's all about magic potions, isn't it?

Now if you who worry about variations of gravity (you don't really, do you?) would get a mass balance instead of a scale, you could eliminate that source of anxiety.

I can show you from experiments I have done that when it comes to phenidone in a PQ or PC developer, the magic ratio of P to Q or P to C can be anything from 1:40 to 1:80 with no practical difference in activity.

My first balance was one of the Lyman powder balances. It is sensitive to 1/10 of a grain and was affordable. Larger quantities, like sulfite, are not usually critical so I don't weigh them out unless I want to avoid controversy in something I'm going to publish.

gainer said:

My viewpoint is that there are two things we should know here. How accurately can I measure, and how accurately must I measure in order to get the results I want.

I can show you from experiments I have done that when it comes to phenidone in a PQ or PC developer, the magic ratio of P to Q or P to C can be anything from 1:40 to 1:80 with no practical difference in activity.

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I agree completely, Pat. I have a balance scale that I bought more than 25 years ago, and shortly thereafter discovered teaspoon measurements. I've not looked back since, and have never had bad results that I could trace to the measuring system I used. Plenty of bad results from improper exposure and other photographer-specific flubs, but none due to improper measurements.

Of course, I've stuck with the same set of measuring spoons for all these years, so whatever gram-equivalent I'm really measuring has remained consistent.

If I get a bottle of Vitamin C that's in crystalline rather than powdered form, I will weigh it to see if my teaspoon amounts need to be adjusted, but rarely has that been the case.

In fact, since converting to the Phenidone/Vitamin C world of developers, my shelf of other chemicals is slowly moldering away. Life is very simple in the darkroom now with my bottle of powdered Phenidone, bottle of isopropyl alcohol, jar of Kodalk, box of Arm & Hammer Washing soda, box of Borax, and jar of Vitamin C. Oh, and a little Liquid Orthazite for my paper developer. Simple and cheap.

Larry

psvensson said:

FYI Larry, you can use half as much carbonate for Delta 400. It's counterintuitive that you can use the same volume of carbonate and ascorbic acid, but it works. 10 mins at 74F gives a contrast range of 1.2. The grain is nice, but the accutance isn't exciting.

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Interesting. I never tried the carbonate with Delta 400. Started with metaborate at 6 minutes at 70 F, and it works so well for both grain and accutance that I didn't try the carbonate. I figured it would shorten the development time too much since it's a more active agent.

I switched to carbonate for Delta 100 and Fuji ACROS and Fuji Neopan, because the metaborate demanded times in the 10 minute range for those films, and I prefer to work with the 6-7 minute range. Even with carbonate, ACROS needs 7:30. But what beautiful tones it has! I shot a contrasty snow scene recently, and barely had to do any burning or dodging. The highlights held beautifully, the shadows were richly detailed, and the midtones glowed.

Larry

With regard to sharpness, as has been pointed out by others, the developer byproducts that ascorbate leaves are acidic. These help give it sharpness, but if the pH is too high, the neutralization of those products might occur before they have a chance to create the effect. I'm just guessing, but it might be worth a little test. Try adding a little borax. I have used half and half borax and carbonate.