PQ vs MQ: Are there attributes to each which define their respective virtues, pro or con?

[David Lyga]

Phenidone A is often used as a substitute for metol; both can be used, separately but effectively, in conjunction with hydroquinone.
But is one really better than the other? And, in all ways?

In sum, what are the positives and negatives for film development in each combination. We know that one needs far less Phenidone A than one needs metol, but, other than that, what are the differences? To those proponents of Phenidone A, I see no lessening of use for MQ developers, so they must be doing something correctly. That said, there is much interest with PQ developers, especially in recent years.

Are there attributes which make MQ better then PQ? And, vice-versa, are there attributes which make PQ better than MQ? - David Lyga

 

[Ian Grant]

PQ developer have far better keeping properties and you can make liquid concentrates like Ilford PQ Universal, also Phenidone gives warmer tones than Metol. It's better in replenished developers because it can tolerate very much higher levels of Bromide and Iodide compared to Metol.

Phenidone/Hydroquinoe fine grain dveloper tend not to be quite as fine grained as their MQ counterparts but do give a slight speed increase. Grain can be finer in conjuction with Glycin, Acorbic acid/Ascorbate, Pyrocatechin etc.

These days many concentrated developers use Dimezones rather than Phenidone, my experience is these tend to oxidise faster once opened compared to the older Phenidone versions.

Ian

 

[David Lyga]

Very interesting; thank you Ian. I guess the sensible question to ask is this: Why has dimezone 'taken over' Phenidone? Essentially I want to hear of negatives regarding Phenidone. 'Fine grain lack' might me one, but maybe not, as Rodinal is not fine grain. - David Lyga

 

[Ian Grant]

Dimezone is cheaper than Phenidone in the bulk quantities needed, also Champion may well have already been using it in some of their own chemistry when Ilford's chemistry manufacture was sub contracted to them. So Ilford's PQ liquid concentrate developers were re-formulated using Dimezone, Phenidone is still used in Microphen and Bromophen.

With some films Rodinal gives excellent fine grain, Tmax and the original Agfa APX100.

Ian

 

[BradS]

In my, admittedly minimal, experience with Phenidone , I have observed that a restrainer, other than the usual KBr is necessary.
The activity level of Phenidone seems to much greater than that of Metol. On of the implications seems to be that Phenidone concoctions seem to be somewhat more unpredictable or less stable those employing Metol.
I think of this in terms of robustness. In my observations, PQ concoctions appear to be less robust that the related MQ concoction.

 

[Ian Grant]

In my, admittedly minimal, experience with Phenidone , I have observed that a restrainer, other than the usual KBr is necessary.
The activity level of Phenidone seems to much greater than that of Metol. On of the implications seems to be that Phenidone concostions seem to be somewhat more unpredictable or less stable those employing Metol.
I think of this in terms of robustness. In my observations, PQ concoctions appear to be less robust that the related MQ concoction.

No PQ developers are more stable than MQ and keep better in concentrate or when mixed in use.

When Ilford first began selling PQ print developers in the mid 1950's the Formulae simply substituted Phenidone for the Metol (not in the same quantity as it's more active), customers complained about colour shifts in prints during printing sessions, This was due to Bromide build up, effectively the developer was becoming more warm toned, as a consequence they reduced the Bromide in the and added Benzotriazole, this stopped the warm colour shifts. Then they deliberately added more Bromide to make ID-78 their Warm tone powder developer, sold for many years. Current Ilford Warmtone developer is just a liquid concentrate version.

I'd add for David that PQ fine grain dvelopers give harsher grain when freshly made up, with replenishment they become finer grained due to the bromide build up, taht was particularly the case with Autophen a PQ variant of ID-11/D76 which was a bulk D&P photo finishing developer.

Ian

 

[john_s]

.......These days many concentrated developers use Dimezones rather than Phenidone, my experience is these tend to oxidise faster once opened compared to the older Phenidone versions.

Ian

I'm surprised to read this. I have read that one advantage of Dimezone-S is easier solubility than phenidone, but I was under the impression that stability was also. I thought that these advantages were the point of Dimezone-S.

 

[David Lyga]

I'd add for David that PQ fine grain dvelopers give harsher grain when freshly made up, with replenishment they become finer grained due to the bromide build up, taht was particularly the case with Autophen a PQ variant of ID-11/D76 which was a bulk D&P photo finishing developer.

Ian

Might I correctly surmise then, that, along with the harsher grain comes greater acutance, somewhat like with Rodinal? - David Lyga

 

[Ian Grant]

Might I correctly surmise then, that, along with the harsher grain comes greater acutance, somewhat like with Rodinal? - David Lyga

With replenished developers as they become seasoned grain becomes finer and acutance increases. I don't like to compare with Rodinal because it's different and some of the finest grained 35mm negatives shot on 100 ISO films were processedin Rodinal.

IAn