Sandro
I’ve got a roll of film here: ORWO UN32. I don’t know what the ISO rating is. Can I work out the (residue) speed by doing test develops and exposures?
TR
Yes, that works. You take a series of test shots on, for example, a black cotton cloth or a black
sock in diffuse, consistent light. The material must not be shiny; it should be matt. The first shot, in which the creases (the texture) are clearly visible, is the one you can use to calculate the actual speed. You should measure the light beforehand using a properly functioning handheld light meter with a dome light sensor. The development time has nothing to do with the sensitivity (or rather, it merely controls the contrast).
Here is a link on the subject:
http://www.silberbild.info/negativ/ISO sensitivity/
Ulf-Benno
Hello Sandro,
UN32 used to be my favourite film. Back in 1994, I ordered no fewer than 61 metres of it to rewind into 37 35mm cassettes. I then used it to produce reversal slides for 12 years. Towards the end, the films lost their brilliance due to exposure, with the blacks turning grey and the highlights fading too. I then used the last few rolls as negative film and exposed and developed them in exactly the same way as NP15 or Orwopan 25 of the same age. So at 15 DIN or ISO 25. The negatives are now rather flat too, but the sensitivity utilisation is better than with OP 25. To still be able to use the film, I developed it for longer and exposed it slightly shorter (18 DIN). The contrast increases again, as does the granularity. However, the material is of a fine grain. A considerable fog cannot be denied. To reduce it, I use heavily diluted developer or heavily used developer. The sensitivity then drops a little again. Overall, however, the UN32 is better than Orwopan 25 and can still be used effectively even after two decades. So, for now, I recommend using the data sheets for the OP25 or NP15 and, in the first test, slightly increasing the development time and keeping the exposure on the short side. I suspect and hope these negatives will turn out very well.
Ulf-Benno
Sandro
Do you know what the speed of that film (ORWO UN 32) was back then? I’d like to develop it in reverse.
Ulf-Benno
I developed the Orwo UN32 slide film using the Orwo A4105 developer kit, with an initial development time of 6 minutes 30 seconds and an exposure equivalent to 18 DIN. For the last few rolls, I increased the development time to 7 minutes to maintain the contrast. The blacks didn’t turn out quite as black as a result. That is why I then switched to Effke 25 and 50, as well as APX 100 and FP4. After 10 years, these films produced better slides than the UN32, despite the grey base. I achieved the best result with the Orwo developer in 2013 using Silvermax at 26 DIN and a development time of 7:30 minutes. Unfortunately, I then ran out of this developer. This was followed by unsuccessful test developments using makeshift recipes from narrow-gauge film forums based on Tetenal or Rollei paper developers. Although slides were produced, they were consistently too flat and too fogged.
The A4105 developer set and its successor, the A4186, are no longer manufactured or supplied. A better alternative would be the reversal set by Klaus Wehner from Paderborn, which unfortunately has not yet been taken up for large-scale industrial production. Here, I would recommend the same development times as for the Silvermax.
However, it is questionable whether this is worth it, as there are better films for this purpose. To reduce the age-related fog, one would also need to work with a heavily diluted developer. For example, a dilution of 1:4 and a six-fold extension of the development time, with a total liquid volume of 250 ml per film, combined with vigorous and constant agitation, could produce a reasonably good result. With modern films, however, the quality would be significantly better.
So good luck!
Ulf-Benno
KlausWehner
I agree with Ulf-Benno’s assessment: it is questionable whether it is worth attempting reverse processing with films that are so heavily over-exposed.
The results will be unsatisfactory.
But of course, experimentation has its own appeal. You can learn a great deal from it.
You will get the best black-and-white slides with fresh, modern films – particularly those designed for reversal processing.
The reversal chemicals mentioned by Ulf-Benno are available from me at any time as a chemistry kit.
Simply send an email to:
klaus.wehner@web.de
Best regards
Klaus Wehner
Sandro
You can make your own ORWO A 4105 developer. I’ve got the recipe lying about somewhere.
Sandro
I've just managed to develop the ADOX Silvermax in reverse with excellent results. (Without the Wehner reversal kit)
Ulf-Benno
You’re certainly quick. Just ordering and weighing out the chemicals takes a lot of time. I’m sure you’ve prepared several litres at once. The developer keeps for years. I would have recommended preparing a 2:1 concentrate to save space.
Years ago, I achieved the best results with Silvermax using Orwo developer. Even with heavily used developer, the results were still better than with fresh UN32. That’s why this film is definitely worth recommending, probably even for amateur recipes. But development with Klaus Wehner’s chemicals is a real eye-opener. Even clearer and with better sharpness. You’ll be amazed.
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Otherwise, I’ve been rummaging through my nostalgia box. I still have a UN32, plus an NP15, three NP20s and NP27s, two OP25s, an APX 25 and an effke 25. I’ve also found the original ORWO product information sheets for OP 25-400, UN52, UN32, Orwochrome RC100 and Orwocolor CNG200. I also have the books “Entwickeln” and “Photographische Chemie” from Fotokinoverlag, which contain detailed descriptions of reversal processing and all the recipes. If required, I can copy excerpts from them, provided I obtain permission from the publisher’s successor.
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Best regards, Ulf-Benno
