Why Pyrol rather than hydroquinone?

Canuck · Jun 6, 2005

Just started into the mixing up my own staining developers. I found a lots of formula dealing with pyrol and catechol but almost nothing with hydroquinone. Did some research on the great wide net but not much in the way of hits (maybe looking in the wrong places) for a staining developer based on hydroquinone. I am not wanting to rehash the old news of staining versus regular developers, but why most formulas have chosen to use pyrol or catechol rather than hydroquinone. Is there a major advantage with grain, accutance, and tone with pyrol or catechol over hydroquinone? I just mixed up a hydroquinone developer (formula from another thread here), so not committed 100% yet to it and just doing more research before ordering more chemicals to play with.

Elvis

psvensson · Jun 6, 2005

I think the reason is that hq won't stain if there's more than a minute amount of sulfite in the developer, and sulfite is the traditional preservative of choice. There are ways of getting around this, of course. As Gainer has shown, you can use an organic solvent instead of water for the stock solution. The other way is to mix the developer from powder right before use. I did this with good results. Hq dissolves quickly in water.

Canuck · Jun 6, 2005

Sounds interesting. I don't recall sulfite as I have it as a two parter and I mixed it up a couple of weeks ago. Developed with it just a couple of times so far. Count is 5 good sheets, to one badly streaked one.

psvensson · Jun 6, 2005

Is this the one modified from Pyrocat by Mehment Kismet? It contains a small amount of bisulfite, which produces sulfite ions. The amount is so small that it won't prevent stain, but neither will it do much to preserve the stock solution, I think. I imagine the keeping qualities could be pretty good anyway.

Canuck · Jun 6, 2005

I think that's the one. It looked like a good one to try since I had all the necessary chems on hand.

psvensson · Jun 6, 2005

I'm tempted to try it myself. BTW, I neglected to mention that the reason it contains sulfite ions is that these are necessary to activate the hq-phenidone synergy. Without them, the developer would be a lot slower.

Are you getting a lot of stain?

Canuck · Jun 6, 2005

Its seems to be working well. Lots of brownish coloured staining. Only bad sheet I got had some nasty streaks of brown on it. Until now, the last few sheets looked fine. Using APX100 at EI=50 @ 8 minutes.

avandesande · Jun 6, 2005

hydroquinone only has two phenolic sites on it vs 3. hydroquinone does not crosslink with the gelatine as readily as pyrogallol or pyrocatechol. Crosslinking is what chemically binds the pyrogallol to the gelatine causing stain.

Canuck · Jun 6, 2005

avandesande said:
hydroquinone only has two phenolic sites on it vs 3. hydroquinone does not crosslink with the gelatine as readily as pyrogallol or pyrocatechol. Crosslinking is what chemically binds the pyrogallol to the gelatine causing stain.

So can I assume that it is due to this that the speed of development is slower that using pyro or catechol? I have lots of staining on my negs so the staining isn't an issue but I guess the development time and the amount HQ used maybe.

avandesande · Jun 6, 2005

HQ does oxidize more slowly than pyrogallol/catechol so this would probably explain the slower speed. It also has a better shelf life for the same reason.

Crosslinking is why pyrogallol is used to tan leather. It actually chemically binds the protein strands together which make them tougher and harder.

Tom Hoskinson · Jun 6, 2005

avandesande said:
hydroquinone only has two phenolic sites on it vs 3. hydroquinone does not crosslink with the gelatine as readily as pyrogallol or pyrocatechol. Crosslinking is what chemically binds the pyrogallol to the gelatine causing stain.

Hydroquinone (1,4-Dihydroxybenzene);
Catechol (1,2-Dihydroxybenzene);
Pyrogallol (1,2,3-Trihydroybenzene).

All three of these Benzine Ring compounds have the potential to act as tanning and staining developers. Sulfites can depress or stop the tanning and staining with all three.

Pyrogallol is the most active of the three. Catechol is less active than Pyrogallol and more active than Hydroquinone. In general, it is possible to substitute one of these reagents for another, taking into account the differences in activity.

All three developers become more active in the presence of sulfite - but with addition of too much sulfite lose their ability to stain and tan.

All three developers are additive (show increased activity) or are superadditive with phenidone and phenidone derivatives.

All three developers are additive with Metol.

All three developers are additive (or superadditive) with ascorbic acid.

avandesande · Jun 6, 2005

It is probably a difference in activity (proportional stain) between pyrogallol and HQ of at least a factor of 4 if not more. So yes, technically it stains but not in a useful sense.
Any of these developer solutions will turn colors and fog the negative. This in not what people are looking for.

psvensson · Jun 6, 2005

Gainer's staining developer gets good reviews from other people. I tried it and did not see a lot of fog. I bleached it out to see the stain. It did not appear very strong, but I haven't tried any pyrogallol or catechol developers.

Canuck · Jun 6, 2005

psvensson said:
Gainer's staining developer gets good reviews from other people. I tried it and did not see a lot of fog. I bleached it out to see the stain. It did not appear very strong, but I haven't tried any pyrogallol or catechol developers.

I haven't tried the Gainer formula (yet) but one thing I have noticed is that fog level is visually higher with the HQ developer than what I get with developing in say Rodinal. What can be done to reduce fog level? Addition of KBr?

psvensson · Jun 6, 2005

Gainer's developer uses TEA rather than carbonate as the activator, so it has a lower pH that may mean less fog. Metaborate could also work.

Tom Hoskinson · Jun 6, 2005

avandesande said:
It is probably a difference in activity (proportional stain) between pyrogallol and HQ of at least a factor of 4 if not more. So yes, technically it stains but not in a useful sense.
Any of these developer solutions will turn colors and fog the negative. This in not what people are looking for.

In my direct experience, Hydroquinone based staining and tanning developers produce useful stain and proportional tanning with low fog.

Canuck · Jun 6, 2005

psvensson said:
Gainer's developer uses TEA rather than carbonate as the activator, so it has a lower pH that may mean less fog. Metaborate could also work.

Next experiment I'll try borax. Since borax is less basic, does that mean my development times needs to be increased?

Mehmet Kismet · Jun 6, 2005

Hi,

I am using since long time, the formula below and the result is what I expect from that kind of developer. The only reason why I am using hydroquinone instead of catechol is very simple because it is difficult if not impossible to have catechol in Turkey.
The keeping properties are excellent, and I think that it is worth to give a try.

Here is the formulae.

Best
Mehmet Kismet

A:
Distilled water : 400cc
Sodium Bisülfite 5g
Hydroquinone 25g
Phenidone 1g
(dissolved in5cc
isopropyl alcohol)
Pot. Bromide 1g
Water to make 500cc

B
Distilled water 1000cc
Sod. Carbonate 200g
(anhydre)

Some data for 4"x5" FP4(EI 64) with JOBO CPP-2 and 3010 drums with rotating speed @P
(N)
10A + 50B + 750Water
8min.@22oC

(N+2)
15A + 75B + 750Water
6,5min. @22oC

psvensson · Jun 6, 2005

Canuck said:
Next experiment I'll try borax. Since borax is less basic, does that mean my development times needs to be increased?

You're going to need a lot of borax to get your times close to what you get with carbonate. I wouldn't go there.

Canuck · Jun 6, 2005

psvensson said:
You're going to need a lot of borax to get your times close to what you get with carbonate. I wouldn't go there.

Hmmm ... more time in the darkroom and this is bad how?

Ole · Jun 6, 2005

Tom Hoskinson said:
Hydroquinone (1,4-Dihydroxybenzene);
Catechol (1,2-Dihydroxybenzene);
Pyrogallol (1,2,3-Trihydroybenzene).

All three of these Benzine Ring compounds have the potential to act as tanning and staining developers. Sulfites can depress or stop the tanning and staining with all three.
...

One of the really interesting things about these developers is that 1,3-Dihydroxybenzene - isn't. A developer, that is. Utterly useless for all developing purposes.

dancqu · Jun 6, 2005

psvensson said:
You're going to need a lot of borax to get your times close
to what you get with carbonate. I wouldn't go there.

You're in a hurry. Mr. Canuck wishes to go where no man
has gone before then return and tell us of his findings.

I will suggest he give a bicarbonate-carbonate blend a try;
perhaps a 50/50 blend by weight for starters. Dan

NER · Jun 6, 2005

Hydroquinone is not a staining developer. It exerts a tanning effect, and has been reported to tan (crosslink) more efficiently than pyrogallol or pyrocatechin [A. & L. Lumiere, B.J. Phot., 285 (1906), and A. G. Tull, J. Phot. Sci. 11 (1963)]. Hydroquionone has less reducing power than pyrogallol because of differences in physico-chemical properties, e.g., redox and bromide potentials. See John & Field, "Photographic Chemistry," 1963, and G. Haist, "Modern Photographic Processing," 1979.

Tom Hoskinson · Jun 6, 2005

Sorry, NER but you are wrong. Hydroquinine (1,4-Dihydroxybenzene) is a staining developer and has been documented as such by many researchers - Including Grant Haist.

In addition, I have a substantial amount of sensitometric data of my own that confirms this.

NER · Jun 6, 2005

Give me a citation - or publish.

Why Pyrol rather than hydroquinone?

Moderator

Privacy & Transparency

Privacy & Transparency