This is kind of a work in process
Here is the tweaked Pyro-Uno formula.
TEA (Triethanolamine) 80 ml
Ascorbic acid 1.4 g
Pyrogallol 3.4 g
Metol 0.4 g
TEA to make 100 ml
Mix chemicals in order listed. I mix with a hot plate stirrer at about 150F. Be patient as it takes a little time for the chemicals to dissolve
Working Solution: 1:50 to 1:200. 1:100 was used for the tests with FP4+.
Remember, this is a one-solution formula that you merely mix with water for the working solution. That is why the uno, which means one in Spanish.
I adjusted the formula to give a developer which when used at a dilution of 1:100 would give a curve very close to that of Pyrocat-HD used at 1:1:100. My testing is based on development in BTZS type tubes with constant, but gentle, agitation.
In BTZS testing five sheets of film are given identical exposures and then developed for a range of times. After the film is dry the negative step wedges are read with a densitometer and the values put into Winplotter. With Winplotter one can then run the program with different print exposure scales to calculate development time for a range of subject brightness conditions. For the testing here I set the ES to 1.35, which I find about right for printing with VC silver gelatin papers.
When you look at the charts you will see that each curve has four numbers. They are from left to right, 1) time of development, 2) effective film speed, 3) average gradient, and 4) SBR (subject brightness range).
The two tests were made with a different light source so the effective film speed is comparatively speaking not 100% correct. Also, the B+F values are not indicative as the Pyro Uno tests were carried out with FP4+ film that has been stored at room temperature for about three years and has developed a small amount of B+F.
Over the next several weeks I plan to carry out some real life tests comparing this developer to D76, and will post the results as they become available.
Thanks very much for sharing this Sandy. I'll be watching your reports, and maybe trying some myself.
How would you compare this developer from a results point of view compared to Pyrocat-HD?
Originally Posted by Lee L
Thanks. I plan to first test it against D76 1:1. That is what I did when I first started working with the Pyrocat-HD formula. D76 is the standard against which all developers must be evaluated for speed, grain, resolution, shelf life and apparent sharpness.
In terms of image quality I have no idea at this time. I really don't expect image quality to be any better, but the fact that this is a one solution developer may appeal to some, and the stain of pyrogallol based developers offers a bit more highlight compensation than that of pyrocatechin based developers with VC silver gelatin papers. In that sense Pyro-Uno would be more a replacement for PMK or other pyrogallol based developers than Pyrocat.
Originally Posted by Tom Kershaw
I adjusted the formula so that the energy level of Pyro-Uno would be as close as possible to that of Pyrocat-HD, for two reasons. First, my belief is that if the energy level is approximately the same with a given type of development, given the fact that the reducer amount is very similar, I would expect fairly similar results in terms of grain and apparent sharpness. And 2), if time of development for a given average gradient is nearly identical this will make any comparisons of grain and sharpness very easy since I just expose and develop both developers the same way. The most important factor in making fair and objective comparisons of developers is to expose and develop so that both give the same density and contrast.
Last edited by sanking; 07-28-2009 at 08:18 PM. Click to view previous post history.
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A pair of questions
May I suppose 20║C as development temperature in your test?
May I suppose 35% more time developing 120 film agitating 5 sec. / 25 sec. stand?
My standard time for development i 21C. And I would only increase time about 20% going from continuous to intermittent agitation every 25 seconds.
Originally Posted by claudiosz
So, if you succed, all we will have to decide is whether we want the cat or the gal.
What sort of shelf life do you expect for the stock solution?
Jim MacKenzie - Regina, Saskatchewan, Canada
A bunch of Nikons; Feds, Zorkis and a Kiev; Pentax 67-II (inherited from my deceased father-in-law); Bronica SQ-A; and a nice Shen Hao 4x5 field camera with 3 decent lenses that needs to be taken outside more. Oh, and as of mid-2012, one of those bodies we don't talk about here.
Favourite film: do I need to pick only one?
The shelf life of a stock solution mixed in TEA should be at least 2-3 years unless the solution is contaminated. The same is true of stock solutions mixed in glycol. This is because because the solutions do not oxidize as they might if mixed in water.
Originally Posted by PhotoJim
Some people have suggested that such solutions might last for decades. I have some doubts about this because all of the solutions I have mixed in TEA, including Gainer's original PC-TEA, have strongly discolored after three or four years. I also have a small container of another single solution pyro developer that I mixed in TEA several years ago and the color, which was very clear on mixing, has also strongly discolored in the three or four years since I mixed it. I don't know the cause of the discoloration but tend to believe it is caused by oxidation.