Experiments with Metol and ascorbic acid.
The factors affecting developer activity are temperature, pH,
concentration, products of aerial oxidation, products of silver halide
reduction, and the orientations of the heavenly bodies.
According to some experimental results reported in "The Theory of the
Photographic Process" as little as 0.05 moles (6.3 grams) of sodium sulfite in
a liter of Metol developer will double the rate of development that is
obtained when no sulfite is present, pH being held at 8.7 in both cases.
It is explained that oxidation products of Metol restrain development, and
that sulfite counteracts these products by forming the sulfonate.
Ascorbic acid will do the same degree of acceleration without sulfite, also at pH 8.7. In this case the oxidized Metol is reduced back to its original form. The ascorbate is itself oxidized and pH is decreased in the process. The decrease in amount of active Metol in the one case or the decrease of pH in the other may not cause much difference in capacity and storage longevity between a Metol-sulfite and a metol-ascorbate developer. However, it would seem that a well buffered working solution might tip the balance in favor of the ascorbate.
I will explore first a 0.05 molar concentration of Metol, which is
approximately that of D-23, together with a 0.05 molar concentration of
ascorbic acid. It remains to formulate the alkali needed to make the pH less
than that at which an ascorbate becomes a developer and great enough to ensure activity of Metol.
I calculate that 0.1 moles of sodium hydroxide will neutralize the 0.05
moles of sulfuric acid attached to the Metol base plus the 0.05 moles of
ascorbic acid, leaving 0.05 moles each of sodium sulfate and 4-(methyl-
amino)phenol and 0.05 moles of sodium ascorbate. The net pH thus far is still
not alkaline enough to develop film in a reasonable time, nor does it have the
necessary buffering action to keep the pH from going lower yet. A few grams of borax should bring the pH up to about 9.2 but even 20 grams will have little
more effect on pH and should give a cushion against reduction of pH during
The resulting recipe is:
Ascorbic acid.....8.8 g
Sodium hydroxide..4 g
Water to 1 liter.
The concentration of Metol is about 13% greater than in D-23 and the
concentration of sodium sulfite is nil.
The pH of this mixture, which I measure with test strips to be about 9, is
below that at which the ascorbate is a developer of any consequence. The
initial activity of the mixture is about that which could have been obtained
with sulfite in place of the ascorbate, so it does not seem that synergism
between Metol and ascorbate is the explanation.
The ratio of borax to caustic in this formula is quite close to the
effective ratio in sodium metaborate. 14.5 grams of sodium hydroxide and 69
grams of borax in a liter make a solution that is often used as a substitute
for 10% sodium metaborate. 276 ml of such a solution, or 27.6 grams of Kodalk if you prefer, will contain the equivalent of 4 grams of sodium hydroxide and about 20 grams of borax. It may be easier to get sodium metaborate than sodium hydroxide through the UPS. The recipe then becomes:
Ascorbic acid......8.8 g
Sodium metaborate..27.6 g or 276 ml of 10% sodium metaborate solution.
Water to 1 liter.
All ingredients are quickly dissolved in room temperature water. HP5+
developed for 8 minutes at 68 F gives normal contrast, showing that the
solution could be diluted. In fact, diluting with an equal part of water
increased development time by only 25%, probably because the pH of this
solution does not change much with dilution. 125 ml diluted with 125 ml of
water did a 36 exposure roll of HP5+ to normal contrast in 10 minutes, which
means of course that a liter of the above formula will do 16 standard rolls
without reuse. As a matter of interest, twice the above recipe can be squeezed into one liter.
By the way, don't be confused by the fact that there exist 4 mol and 8 mol
metaborates. A gram of one has the same number of atoms of sodium, boron,
oxygen and hydrogen as a gram of the other. At 53.6 C, without losing any
water, Na2B2O4.8H2O becomes NaBO2.4H2O which is stable to 105 C. In other words, the distinction between 4 mol and 8 mol sodium metaborate is academic, not practical when we specify solution strength in terms of weight per unit volume. You may see this for yourself at www.borax.com.
I am attaching a scan of a 10x print from FP4+ developed 8 minutes, 68 F. This is not of very high resolution, but may serve to illustrate gradations. I have also attached a higher resolution scan of a small part of the same print. If you print the high res. scan to 6x9 inches, you will see about a 50X magnification of that part. I have no idea how these will show up, but you can imagine that the originals are better.
As it turned out, the attachments showed up at the end of the thread on superadditivity started by PE. My fault.
Last edited by gainer; 06-03-2007 at 11:23 AM. Click to view previous post history.
It is a repetition of data published by ANSI.
Originally Posted by Photo Engineer
Many, many beginners in many places have used my developers made mostly from things you can get at the grocery or hardware or country general store using common measuring spoons and have been inspired to continue photography. I made most of my photographs of musicians using homebrew without benefit of anything more accurate than a cheap spring kitchen scale.
You still haven't tried to find out if there was a reason why I could not find your reference to potassuim in fixer in my copy of Mees and James, nor explained why you should expect to find significant amounts of any potassium compound in any grade of borax. Nor have you told us what brand and grade will meet your specs and how you know it. Potassium compounds are among the first to be separated in the processing of raw borax. They are among the easiest to reduce to undetectable amounts in the purification of borax.
I don't have to explain or locate anything. I have it here in 3 texts and I took the excerpt from one and posted it here.
You had said quote: "I have tried to tell you that I did NOT publish the ANSI-PMA standard. " and here you say it is a repetition of data pulished by ANSI and posted by you here. So, you did post it.
I merely questioned the utility of the data.
In fact, photograde must apply to all stages of photochemistry, and thus you cannot have a developer photograde and a fixer photograde chemical. Photograde is photograde and a photograde borax must be free of potassium and that should be in the specifications. This alone renders the specification above suspect to me.
I'm glad people love your chemistry instructions, but I warn you that there is up to a 20% error in volumetric measurments of solids. This can affect image tone and speed among other things if the error is in bromide being used for a mix of D-72 (Dektol) for example.
So, there is playing in the darkroom for fun, and high quality darkroom work.
For that matter, in emulsion making and coating, I am restricted to what amounts to me as playing due to the limitations in chemicals and equipment available on my budget. But, I do try to keep the lab procedures as correct as possible.
BS, MS, Piled Higher and Deeper.
I don't have to explain or locate anything. I have it here in 3 texts and I took the excerpt from one and posted it here."
Surely you did, and you called me an idiot for not being able to find the one quote I should have had at hand. See the attachments.
" So, you did post it.
I merely questioned the utility of the data."
And now you are trying to shoot the messenger. Make your question available to ANSI. Maybe they'll listen to you.
"In fact, photograde must apply to all stages of photochemistry, and thus you cannot have a developer photograde and a fixer photograde chemical. "
That is a stupid comment. We have had for years different grades for precision lab work and practical photo processing. You yourself or Kirk said that Kodak used ANSI specs in production.
"Photograde is photograde and a photograde borax must be free of potassium and that should be in the specifications. This alone renders the specification above suspect to me."
before you suspect it, you should look into the probability of potassium being in technical grade borax.
"I'm glad people love your chemistry instructions, but I warn you that there is up to a 20% error in volumetric measurments of solids. This can affect image tone and speed among other things if the error is in bromide being used for a mix of D-72 (Dektol) for example."
Before I "published" the article for Petersens Photographic in 1973, I did statistical sampling tests of the chemicals I proposed fot use. I also did tests where I varied the measurements by more the the 3 sigma amount. I gave methods for determining the number of teaspoons in a pound or other weight unit that came from a manufacture like Kodak so that the variation from one batch could be accounted for.
So, there is playing in the darkroom for fun, and high quality darkroom work.
"For that matter, in emulsion making and coating, I am restricted to what amounts to me as playing due to the limitations in chemicals and equipment available on my budget. But, I do try to keep the lab procedures as correct as possible."
You are not the only quality conscious person around. You may be the only one who believes implicitly in the label on the package you get.
I most assuredly did not call you an idiot. Please don't misquote me.
Now, as for your post from Mees. Do you notice that Potassium Thiosulfate is not shown? The reason is that it is not a good fixer. That is the reason it is NOT in the graph nor mentioned in the paragraph you posted. It also is the reason why I posted the definitive statement from Haist which gives further references. So, the charts show nothing but the fact that Mees and Mees and James omit Potassium and show that fixation rate varies with Cations such as Sodium, Ammonium and Lithium.
It is a shame you didn't see the adjacent table in which Potassium is cited with a "-" denoting inactivity, and in another table where an optimized Potassium fix was 4x slower than the others.
In addition, I said that there cannot be multiple standards for photo grade chemicals, otherwise we would need one for every use, such as Borax for fixers, Borax for Developers and etc. So, in fact there must be one standard for photograde Borax and it must include potassium ion. You seem to misunderstand that simple statement.
I am stating this to show you again why I said that the standard and the tests were meaningless, and that is all.
I do not believe implicitly in the label and that is the very essence of my questioning. Conversely, you appear willing to accept the label and the standard with no questions attached. I am able to spot flaws in the standards and statements on the labels through experience and questioning the label. If you do not believe what I have said, you should go back and see that I have questioned the labels and even the standards, whereas you have defended them. In fact, that is the essence of this entire disagreement.
I am surprised that you didn't know about the effects of Potassium ion on fixation. That is actually rather well known amongst Photo Engineers.
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Some information to add to chemical purity questions
Here are two photos I just took. They are digital, forgive that. They merely underscore a point for Analog photographers.
The first, on the left shows 3 mounds of Sodium Chloride. The one on the left is a white powder and is Analytical Grade, the one in the middle is Technical Grade and is lumpy. The one on the right is pure white and consists of pure cubes. It is food grade table salt.
The one on the left is suitable for emulsions or processing solutions. The one in the middle works in most processing applications but cannot be used in emulsion making due to aggregation and fog. The one on the right contains Iodide salts (in various states as pure NaI is unstable) and it contains silicates. It cannot be used in either processing or emusion making. Appearnce wise the one on the right appears to be the best, but it is not.
Now, the second picture shows two mounds of salts, KBr (Potassium Bromide) and both are analytical grade. One, on the right, is a powder and the other consists of cubes. The cubes cannot be measured by teaspoon due to their shape and the difficulty forming an full teaspoon evenly, so I used the small cup in the background.
That cup will contain 17.2 grams of KBr in cubic form but will contain 20.4 grams of the powder. This is the type of error to expect when measuring out solids using spoons.
I test my premises about accuracy and purity by actually running tests.
You didn't pick a very good example of possible errors in volumetric measurement. Never did I suggest that potassium bromide or sodium chloride be measured by the teaspoon. There are certain chemicals that are best made up in solutions. If I buy 100 grams of, say, KBr from PF and mix it in water to make a liter, and measure it into my developer a teaspoon (5ml) or a tablespoon (15ml) at a time, where is the error? If I give a formula in grams and ml and an alternate workable formula in teaspoons what is it to you? If I give it only in spoonfuls, you can always weigh out the spoonfuls the first time and use the same weights from then on. You're going to have to do your own tests anyway.
"It is a shame you didn't see the adjacent table in which Potassium is cited with a "-" denoting inactivity, and in another table where an optimized Potassium fix was 4x slower than the others."
Well guess what? Those tables are not there. BTW, what is the number of the printing of your copy?
I have two editions. Mees - Revised Edition, and Mees and James, First Edition. But in addition to all else, I would point out that I knew Howard James personally as well as Grant Haist and others and so got a lot of information in discussions and meetings than is published.
After you look at the table I have more information for you.
As for volumetric measure of solids and chemical purity, there is ALWAYS the potential for up to 20% error regardless of chemical, and regarding purity, I test my own.
As for liquids in a teaspoon or tabelspoon, there is the meniscus to consider. That is why a graduate cylinder is transparent, or didn't you know that.
Also important is whether the liquid is wt/vol or vol/vol or wt/wt, all three of which are used commonly for solutions. Generally, viscosity and illumination level are used as criteria as to which is used in a professional darkroom.
Here are some generic examples where people discuss your advice to use volumetric measures with solids. It covers a wide range of chemicals. Also there is a quote below. If you do a search on teaspoon+gainer+photo.net you come up with pages of text with either your generic advice to use volumetric measure or others commenting on it. In my post above, I show a simple test to reveal the fallacy in that method which can yield errors of about 10% - 30% depending on crystal habit. It does not matter that I picked KBr, what matters is crystal habit. Crystalline Ascorbic Acid vs powdered Ascorbic Acid can show the same problem. It is a sad commentary on your understanding of this that you have not recognized the error in your statement regarding my use of KBr.
I would also like to add that we have had this entire fruitless discussion a year or more ago to no avail. I gave data at that time as well but it seems that it was ignored. I even pointed out that in one bottle the crystal habit can vary as the large crystals in a jar move to the top. Thus a spoonfull of a chemical can vary as you use one single bottle.
"It is easy in teaspoon measure. 2 tsp acid and 1 tsp baking soda (not powder)to the liter is close enough,......."
As it becomes more difficult to get prepackaged processing chemistry, we must develop and foster good lab technique in those who will follow us otherwise we fail those future analog photographers.
I myself emphatically do not recommend volumetric measure of solids for serious photographic work.
Ascorbic acid powder purchased as a vitamin has on its label the gram equivalent of a teaspoonful. I have had many different brands and all have said the same.
You and I can argue all we want and we will never come to agreement. If I say you are right about something, you will find something wrong with the way I said it. Part of the problem is that you do not see the arguments I make.
How can I see the tables if I do not have them available. What do you know about potassium in borax that is not published in my copy, Third Edition, 1969, Fifth printing?
I find that the first process in production of borates from raw ore separates potassium borates. Potassium borate is 25 times more soluble than sodium borate, so it should be an easy job. If I needed a small amount of extra pure borax, I could do it myself.
Yes, it started years ago. You warned me about flashpoint, but did not seem to know the definition of flashpoint. If you wanted to prove my use of volumetric measures inaccurate, you could have weighed the volumes I presented, varied the weights by the amounts you suppose to be the probable errors and showed that they would not work. The fact is, you could not do that with any formula I proposed.
I'm not a dummy. I look for ways that allow others to enjoy photography who cannot afford even a simple powder scale, such as some underpriveleged children in New Zealand. You seem to be dedicated to telling them they are not entitled to do so if they can't afford analytical grade reagents and laboratory balances. I suggest if you want to carry on this way, you do it by PM.
I am all for both methodologies but one must be differentiated from the other. One is professional and one is by necessity and that must be clear to the user and he/she must know the reasions behind both.
Several years ago I did try to show you the volumetric vs gravimetric measurements and the errors involved and you disagreed with me then just as you seem to now. I gave an exact figure on Photo Net in my post about 2 years ago and here we are again at the same point.
As for flashpoint, I had to explain it to you. You were advocating a potentially dangerous method of mixing chemistry that could cause a flash fire. You see what lack of experience or knowledge can cause? It can lead to a fire in someone's home and I was trying to HELP you avoid a potential law suit.
So, what is in the Potassium data? The chart is totally in error in all versions of Mees. That is apparently why Howard left it out of Mees and James. It reports no data for Potassium and suggests that Ammonium hypo is slower to fix than Sodium hypo, a gross error. So, the figures were corrected in Haist.
It seems that the Cation of Hypo is critical in fixing and therefore must be a criterion in the purity of any generally used photochemical. We did not confirm that until just before Haist published, but after the last version of Mees. So, there must be a maximum allowed level of Potassium in the spec for Hypo itself, you see?
This, BTW, is at the root of the controversy involving TEA in fixers. I will only comment that in a TEA containing fixer, it behaves as the Cation (the ion with a positive charge) and this is where there may be problems. IDK due to uncertainties in published literature.
Design of photographic solutions requires years of work and study Patrick. I am willing to help, but not willing to see information go out with errors by omission or comission. Please see my POV for the sake of the future.
I respect the work you have done for those not able to use weight measurements, but I would like to see the differences and problems explained. The same is true of using grocery store chemiclas. It is important, or we can begin a backslide.
After all, what use is it to pay a premium for a film product from Kodak Fuji or Ilford only to process it in the equivalent of laundry detergent?