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.
20 Mule Team is probably their supplier of the raw product.
Somehow I thought this company 'made' chemicals, but obviously not mineral-based ones, and I'm not aware of borax fields here near the Great Lakes...so you're probably right (of course, as usual, etc)..
I confirmed Chlor Out IS a current product, but considered 'specialty', per CSR, mainly for people who make mistake of over-chlorinating.
I wasn't impressed with the price, but picking up locally beats shipping a heavy tub from out of state and probably makes the local price more realistic.
MSDS for Haviland Chlor Out
Got a deal. 25# $39 local pickup. $63 + shipping online (huh?) Hope I don't get burned by impurities as warned by PE.
Now I have no excuses not to start homebrewing.
Last edited by Murray@uptowngallery; 10-19-2007 at 11:30 AM. Click to view previous post history.
So...uh, do you recommend pre-washing the film with this stuff?
I mixed up a liter of this stuff (2.5g Metol, 9g Ascorbic Acid, 25g Borax) about a week ago and tried it last night. The fresh developer goes in nice and clear and, with TXP at least, comes out a very, very interesting blue-purple color!
I did 8 minutes and got a very delicate neg. If I had a 5x7 enlarger, it will be easy to print. I'm not sure how it'll contact.
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Brad, I'll guess your question is for Patrick about pre-wash.
Isn't presoak usually done in water?
I just added the additional info on pool chemicals for those interested. The last one I listed is for simple fixer.
Yes, I'm asking Patrick if he suggests/recommends pre-washing the film with plain water prior to development in the Metol-C developer proposed here.
My appologies for the confusion.
It has been a long time since I prewashed any film before any developer. There was a time when I routinely prewashed TMX with a wetting agent because otherwise I had problems with air bells. I don't think TMX does that anymore.
I had a complicated scheme for prewetting ready to post but couldn't see the value of it. If you do prewet, I would suggest using a small amount of nonionic wetting agent in the prewash. Something like propylene glycol, maybe. It may be that keeping Phenidone or p-aminophenol base in glycol to mix with the ascorbic acid-borax solution will preclude the necessity of prewashing.
If you are concerned about the dye that doesn't wash out in the developer, it should come out in the fixer. Most developers have enough sulfite to bleach it out.
Um, PG (no, no, not Propylene Glycol, the other guy, Gainer), I'm following your sulfite-free recipe. (acetaminophen, Na-ascorbate, Lye, Borax, water. Hmm, I see a Lorax acronym hiding in there).
If there's dye left over, what then, does it mean anything (like a staining developer), say a magenta dye that would affect contrast with VC paper?