Ian - Let's suppose one mixes 1L of Ilford PQ Universal and 1L of Liquidol. If the person made 10 prints then bottled up the working solution and then 6 weeks later decided to print again, would they have to mix another batch of Ilford PQ Universal? My experience suggests, that Liquidol would be fine, can that be said for the Ilford PQ Universal? The fact sheet for Ilford PQ Universal says mixed working solution bottled lasts 24 hours. If our OP is a small potatoes printer like me, the difference between Liquidol and the others is noteworthy in this regard. Lasting on the shelf is one metric, lasting mixed on the shelf another. If we assume that both PQ and say Liquidol might last undiluted the same amount of time (based on your experience with PQ), then the consumer might want to consider the longevity of mixed developer as a possible advantage of Liquidol....
Why is this bit something the consumer should consider? Print developer is not one shot like say film dev (eg Rodinal).
Thanks for the education.
I might go back to drawing. Please don't recommend a pencil. ( ^:
I happen to like the tone and contrast of Ilford PQ. But, as a liquid, it lacks a long shelf life. That drove me to more frequently use LPD powder mix. LPD is more or less similar in attributes to PQ but lasts 2 to 3x longer when mixed to stock solution in hard plastic bottles. Its results are more consistant (depending on through-put) than 130, an excellent developer.
I may be different but my real photo cost is time and not photo chemicals. I aim for consistant results so I use fresh developer. When I have not, I initially thought I had good results but discovered more sparkle when replacing the used developer.
This is a complex issue because we have no standards, it's bad practice to keep reusing and storing working strength paper developers which is why all companies don't recommend it. Having said that though I know people who use PQ developers in Nova slot processors and replenish and they last weeks dilute.
Originally Posted by zsas
One issue is print quality with any developers stored partially used and there's to many variables, there would almost certainly be shifts in tones with warm tone papers and then some papers have a degree of developer incorporation so are least affected by developer degeneration.
It's about 50 years since I made my first prints and in all those years I've never needed to store part used mixed print developer. I've used PQ developers for over 40 years without an issue and yes stored for over 2 years.
An interesting aside Ilford's sub-contractors now use Dimezone and I've only seen people complain about the shelf life since that change. I make up my own chemistry in bulk, I re-jig the formulae to allow similar concentration to comercial offerings. Because I was spending most of the year abroad and only 2 visits a year back home and a darkroom I've pushed sorage far more than in the past. A PQ developer in a part filled 5 litre bottle will last me over 2 years.
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I have been mixing, testing and using developers for over 60 years and I have found, by doing it professionally, that you must be conscious of the potential chemistry going on, and you must devise a standard process test and a standard keeping test. The process test must consider capacity and change per unit usage. The keeping test must allow for the concentrate and mixed working solution. It must consider factors such as how much your first print is equal to your last print (seasoning).
In the end, it means that your first print from a mix of developer should equal your last print, that a lot of prints should be able to be run, and the time span should be maximized.
This is a long and lengthy process. It is also, to me, fun.
And I assume that happened during a time when b&w processing went from a five days a week eight hours a day business to something done by amateurs once a week or less ... As you stated yourself, working solution shelf life was a non issue for you because you tend to exhaust the developer long before it's near the end of its shelf life. If I print a few dozen 10x15cm test prints then a few 30x40cm prints, I need 2+ liters of developer yet exhaust less than 10% of it. Yes, I do like to use these 2-3 liters of dev for a couple of weeks, fortunately Ansco 130 allows me to do that, and more.
Originally Posted by Ian Grant
Now looking at different Phenidone versions (for non chemists like me):
- Phenidone's developing properties were discovered by John David Kendall and patented as GB542502. You can find the GB patent here, but since the same thing was also patented in the US, it's easier to read the equivalent (but later) US patent US2289367.
- If you look at the structure of Phenidone and what was patented by Kendall, you see that he covered all kinds of substitutions, but only one substitution in the 4 position (the N which attaches to the Phenyl group is position 1, the N right next to it is position 2 and so on), so Kodak used Phenidone variants with 2 substitutions on position 4, most notably Dimezone S, which is 4-Hydroxymethyl-4-Methyl-Phenidone.
- Substitutions in the 4 location seem to improve something so Ilford went ahead and used
, which is 4-Methyl-Phenidone. Most of Ilford's MSDSs don't list the primary dev agent, but the one for Ilfotec HC Developer does, and sure enough it uses Phenidone B.
- Kendall's patents have expired decades ago, so would have any Kodak patents covering Dimezone S. If Dimezone S was profoundly better than Phenidone B, Ilford would have likely switched by now. Same thing goes for Kodak if Phenidone B had some profound advantages over Dimezone S.
- If you order "Phenidone" from Photo Formulary, you apparently get the original version of Phenidone without substitutions in the 4 position, also named Phenidone A. From what I read here both Ian and PE agree that Phenidone A is not long term stable. Formulary's web page doesn't offer Phenidone B, but they do offer Dimezone S. Artcraft only carries Phenidone A. Both Ian and PE would likely agree that Dimezone S is the better choice than Phenidone A if long term stability is needed.
What does this mean for us? If you want to mix a long shelf life developer yourself, get Phenidone B or the more easy to get Dimezone S. For all other applications, Phenidone A is much cheaper, works in lower concentration and is easier to obtain.
And one more thing about seasoning and consistency: since Phenidone and friends don't respond to Bromide as much as Metol, seasoning effects should be much less than with older print devs. Note that, for example, Xtol can be replenished with Xtol.
Trying to be the best of whatever I am, even if what I am is no good.
In my case it means I keep buying the same Phenidone from my current sources, yes I tend to exhaust my PQ print developers whne mixed up, but I also use far less when I know a session is only a few prints.
Originally Posted by Rudeofus
I make commercial strength PQ parer developers so fairly concentratedand substitute the Sodium Carbonate with Potassium Carbonate and Hydroxide, I don't have any issues with storage and with living abroad for 7 years was often leaving part full bottles for months between intensive printing sessions when back in the UK. I should have split it into smaller bottles but it lasted.
There's posts in threads on APUG (from US members) commenting about how well their PQ developers last and how they store part used and re-use them so the US Phenidone must be similar in terms of its stability.
The Ilford Axford-Kendal Fine grain PQ developer sold as Autophen (a PQ variant of D76/ID-11) had an extremely long working life replenished, it just didn't collapse like D76/ID-11.
Ian, you quoted Grant Haist with the statement that Phenidone A is unstable. Nobody questions that Ilford can and does make long lasting developers and a fair section of my last post here describes in excruciating detail why this is so.
When we judge shelf life of developers, we need to be aware that modern photographic paper is very immune to variations in developer compositions. When I started printing, a photo supplies store sold me (high contrast) Dektol and (low contrast) Centabrom S so I could develop for variable times in two trays for fine tuning the contrast of my prints. Long story short, nobody in my darkroom could tell the difference between the same print developed in Dektol only or Centabrom S only.
Why is this relevant here? If you have only a third of the recommended amount of Phenidone in your developer, it may act a bit slowly but will still work and yield very comparable prints. So what people describe as long shelf life in their home brew Phenidone A based developers might be the result of paper makers doing their homework very well.
Trying to be the best of whatever I am, even if what I am is no good.
Many modern papers contain developing agents. You can test for this by taking a piece in the light and adding a drop of plain alkali. The presence of an incorporated developer tends to normalize the results in the developing solution you use.
In addition, Phenidone powder developers are more stable than liquid concentrates, and the pH of a final developer or concentrate will affect the rate of hydrolysis of a Phenidone developer.