Glycin-only developers "assumed to be one stop slower" -- Why?

grainyvision · Jun 17, 2020

Alan Johnson said:
Re: the chemistry of development by glycin, I had a quick look at the books by LFA Mason and by Mees &James and neither cover it.
In "Basic Photo Science " by Walls & Attridge p181 it is mentioned that glycin is in the same family as metol.
In Mason "Photographic Processing Chemistry" p75 it is said that the oxidation of p-aminophenols can proceed in two one-electron steps, the first being production of semiquinononeimine.
IMO this primary developing agent metol probably produces a semiquinoneimine which can be reduced back to metol by certain secondary developing agents, ascorbate would fit the bill.
I would suggest that glycin adsorbed on the grains is similarly oxidized then reduced back by ascorbate.
In "Photography theory and practice vol 4 monochrome processing " by LP Clerc p 496 it is stated:
"Glycin is very sensitive to bromide and with alkali carbonates affords a slow working developer which gives low contrast and and has good keeping properties"
The low contrast mentioned appears very likely why Crawley added metol to glycin in his FX-2 two solution developer.
IMO, here the oxidized metol or glycin is not reduced back but reacts with sulfite to give a monosulfonate (Mason p78).
Crawley, BJP Jan27 1961 p42 says that FX-2 gives an 80% speed increase with certain films of that era.

I'm really curious why glycin can function as a reasonable developer all on it's own even without sulfite while metol can not. My EXG1 developer is just glycin+TEA+carbonate and produces fairly normal contrast and what at least appears to be full speed. Using just glycin+TEA the pH seemed to be too low for full speed, but did produce a reasonable reduced contrast image at 1 stop of over exposure. Also this style of glycin suflite-free developer has a surprisingly long shelf life. There is no obvious color change even a few hours after mixing, but after a day it produces an oily brown scum.

Alan Johnson · Jun 17, 2020

I haven't dug out a reference for it but I believe the oxidation product of metol may inhibit development. It is possible that the oxidation product of glycin may not do this.
IMO FX-2 two solution developer lasts a lot longer than GSD-10 which also produces a precipitate after a time.

grainyvision · Jun 17, 2020

Alan Johnson said:
I haven't dug out a reference for it but I believe the oxidation product of metol may inhibit development. It is possible that the oxidation product of glycin may not do this.
IMO FX-2 two solution developer lasts a lot longer than GSD-10 which also produces a precipitate after a time.

I imagine that GSD-10 would also have a similar shelf life if the carbonate was kept separate. Glycin seems rather unstable at carbonate pH for long-term shelf life. However, Ansco 130 of course throws that theory out of the window as well with it's long life even if kept in an open tray.

DREW WILEY · Jun 17, 2020

Pere - I've had Sinar cameras in some awfully precarious places in younger years. But the best local California climber I know who relocated to the Pyrenees was from there to begin with. He offered to get me high enough on Dhauligiri in Nepal to set a large format world altitude record, but I wisely decided to get married that year instead. Shadows can get intensely blue at high altitude, yet I often used a 29 deep red filter with TMax. Some of my early pre-pyro negs were hard to print, but I've since gotten excellent results with our modern high-quality VC papers, and sometimes a bit of masking too.

138S · Jun 17, 2020

DREW WILEY said:
Some of my early pre-pyro negs were hard to print, but I've since gotten excellent results with our modern high-quality VC papers, and sometimes a bit of masking too.

Not surprising, TMax linearity in the hihglights end in high densities that are not easy to print, pyro + VC solves that problem, stain in the highlights blocks blue so you print those highlights with a lower contrast grade, which it's easier.

DREW WILEY · Jun 17, 2020

I often also print the VC paper thru a deep blue filter to get a full range a microtonal values. So the pyro stain is just one factor among several. But TMX100 delivers poor edge effect even in pyro, so I'm using a non-pyro tweak for it. TMY400 is a different story, but alas, getting expensive in 8x10. But it is also one of those few films where a deep 29 red lends a little something special to the extremes which an ordinary 25 red does not.

Lachlan Young · Jun 17, 2020

Alan Johnson said:
IMO, here the oxidized metol or glycin is not reduced back but reacts with sulfite to give a monosulfonate (Mason p78).

Which would certainly make a case for why HQMS rather took over as the developing agent of choice.

Anon Ymous · Jun 18, 2020

@earlz The Wheatcroft patent isn't of much use IMHO. While it is true that hydroquinone will be oxidised by hydrogen peroxide and give quinone (p-benzoquinone), this has to be performed in very specific conditions and will give different products depending on several factors. When sodium sulfite is present, peroxide will react instantly with it and oxidise it to sulfate. Just try it yourself and have a thermometer in the solution; temperature will rise instantly.

I have a strong suspicion that the most reasonable path to HQMS is via HQ reaction with sulfuric acid. I haven't tried it and is by no means an easy task, but seems to be the simplest. This gives you the acid, which you can react in solution with KOH and get HQMS-K.

But quite frankly, Suvatlar sells the stuff for a very reasonable price, so ask them first before making any bold attempts to synthesise it ...

grainyvision · Jun 18, 2020

Anon Ymous said:
@earlz The Wheatcroft patent isn't of much use IMHO. While it is true that hydroquinone will be oxidised by hydrogen peroxide and give quinone (p-benzoquinone), this has to be performed in very specific conditions and will give different products depending on several factors. When sodium sulfite is present, peroxide will react instantly with it and oxidise it to sulfate. Just try it yourself and have a thermometer in the solution; temperature will rise instantly.

I have a strong suspicion that the most reasonable path to HQMS is via HQ reaction with sulfuric acid. I haven't tried it and is by no means an easy task, but seems to be the simplest. This gives you the acid, which you can react in solution with KOH and get HQMS-K.

But quite frankly, Suvatlar sells the stuff for a very reasonable price, so ask them first before making any bold attempts to synthesise it ...

Personally I get enough hydroquinone "fun" (ie, smelly) with my lith developer formulation stuff, so I have no interest in trying to synthesize HQMS. If a good and economical source becomes easily available in the US I'd like to try out some things, but otherwise I already have way too many developing agents to choose from in my cabinet and I've got at least a decade or two of learning just in figuring out how the common ones work. My interest in Glycin is primarily only because it can be used without sulfite, unlike every other developing agent excluding ascorbic acid (which is practically impossible to use alone)

Glycin-only developers "assumed to be one stop slower" -- Why?

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