PQ Universal developer.

 It's a funny thing that Ilford sell a liquid developer called PQ Universal, suggesting the developer can be used to develop film and paper, but then go on to state in their datasheet that they don't recommend the developer for 120 or 35mm film use, though sheet film is okay.

This kind of contradiction is the kind of thing that will intrigue my brain and cause me to want to investigate further.

So investigate I have.

Film developers fall into two broad categories.  These are;

1.  MQ (Metol-Hydroquinone) based
2.  PQ (Phenidone-Hydroquinone) based.

The MQ or PQ formula utilises the effect that the two developer agents, Metol and Hydroquinone are "superadditive" when used together. The development process will cause Metol or Phenidone to become oxidised and therefore it's effectiveness as a developer will be reduced.  The addition of Hydroquinone to Metol or Phenidone has a recharging effect on Metol or Phenidone, making the developer much more stable in use.  This will allow more films to be developed in a solution than with a single development agent alone. The superadditive effect also prevent sudden death syndrome in film developers, which was previously an issue, certainly in the commercial processing laboratories.

Examples of MQ developers are ID-11/D76 and Adox FX-39 II. Examples of PQ developers are Ilford DDX, Kodak TMAX developer and Microphen.

The introduction of PQ developers, in general,  in the 1950s was to add stability to developers and reduce development times. The reduction of development times was important to commercial processing laboratories who could then process more films in a day. In the 1950s, normal people had the disposable income to buy a camera and shoot films during family events. During this time most people would drop their film to the chemist who would in turn send the film to a commercial lab via a collection service.

A downside of MQ developers is that Metol is a skin irritant and can cause dermatitis, especially for those poor folk who worked in a commercial lab, processing hundreds of films in a day.  PQ based developers simply do not cause the same skin condition and are seen as a less toxic and safer developer than MQ based ones.

Another point to consider with the rise of commercial processing labs is that the camera film itself would need to be consistent in use, but able to be processed in a batch system.  Labs wouldn't gather, for example, all the Tri-X together and process them all at once, no a developer was required so that you could process all 100 speed films together. If you look at the Massive Dev Chart today you'd think that each film needs different times, different developers etc. To get the best out of each film, this may be true, but to process family snaps and general photography you can get away with being more general.

Ilford PQ Universal was once also sold by a chemical company called May and Baker under the trade name Suprol. May and Baker supplied all of the commercial processing labs in the UK and used to sell Suprol by the drum.

Looking at the instructions for Suprol in machine developing, you can get the time down to a less than two minutes per film and all films can be developed with standard times. They simply don't distinguish between the different ISOs.  

Suprol can also be replenished to keep a tank of chemicals working indefinitely.

With automation, made possible by machinery and electronic timing systems, you can be consistent in processing films and get decent results for all film types, certainly good enough for family snaps.

I should say that hobbyist photographers were likely to shun commercial labs and use a smaller processing lab that could treat their precious film with care and hand develop it according to the instructions provided by the photographer during the 1950s  and 1960s.

Suprol is described by May and Baker as a fine grain, high acutance developer.

The thing about the chemical industry is that the formulas used seem to be common knowledge. Hence you get Ilford ID-11 and Kodak D-76 being identical when dilutions and timings are considered and also give identical results (i.e. they are interchangeable).

So it's no surprise that while May and Baker produced industrial quantities of Suprol, Ilford produced an identical product and called it Ilford PQ Universal.  I use Fotospeed PD5, which is identical to Suprol (still sold by a comapny called Champion) and Ilford PQ Universal, but is much lower cost. Even the data sheets are identical, apart from branding.

I use PD5/PQ Universal/Suprol at a dilution of 1+29. This gives me the ability to develop 14 120 films in 250ml of developer, when diluted as a one shot developer for each film.  That means that one litre of undiluted developer will process 56 films.  So from my point of view it's ultra economical.

For me the use of PQ universal is like having all the advantages of Rodinal Acutance, without the grain.  I know some people "Frankenstein" mixtures of Rodinal and D-76 to get similar results.

As far as use is concerned, the dilution of 1+29 gives similar development times to D-76; in fact where no timings are given for PQ Universal, I often use the D-76/ID-11 timings as a starting point.  My agitation scheme is to use Ilford agitation, although I reduce the initial agitation from one minute to 30 seconds and am very gentle with the inversions, we are not trying to emulate a Hotpoint Twin Tub.  Agitation builds contrast fast and so for normal contrast negatives, gently Bentley is the way forward.

PQ Universal can be used to push films, with the associated longer development times.  Lower dilutions of 1+9 or 1+19 have really short development times and standard processing methods will produce high contrast negatives.  This is great for copying documents but not for pictorial uses, unless one is trying to emulate Dido Moriyama.

All photos in this blog were taken by the author and developed in Fotospeed PD5 at 1+29.