Pre-washing (wet) the negative

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Should one pre-wet the negative before developing ? some say no, others do this all the time. What would be the difference ? if there is one ?? Many thanks for your feedback !!

-- Stavros Vogiatzis (stavros@athensintercon.gr), August 23, 2000

Answers

Personally, I only pre-wet when I am developing at higher than room temperatures, in order to acclimatize the film and avoid shocking it with the temp. change (for example, if I am developing at 75deg.).

-- shawn (shawngibson_prophoto@yahoo.com), August 23, 2000.

The only systematic test results I've ever seen (Phil Davis) indicate that response of various films vary perhaps randomly to a long pre-wet of five minutes; some gained contrast, some lost contrast, some gained speed and some lost speed. Compensation of development time or EI for a long prewet (as recommended by Jobo) isn't predictable by any common amount and can be determined only by testing your materials.

Phil also found that a short prewet (one minute) has negligible effects on EI or CI.

He didn't address other reasons given for a prewet, such as the prevention of airbells or to promote evenness.

I've experienced airbells when developing rollfilm in a Jobo rotary processor without the use of a prewet; oddly enough, this was with Xtol, a developer for which Jobo specifically recommends _against_ using a prewet. A one-minute prewet solved the problem with no unwanted effects.

Uneven development is a symptom of insufficient agitation or non-random agitation movements, usually during the first 30 seconds to one minute of development. A prewet will not cure any of these problems.

According to Ilford, their films incorporate a wetting agent in the emulsion and a prewet should _not_ be used because it'll wash out the wetting agent and may cause some of the problems the prewet is expected to prevent. I have no idea about other brand films.

So you need to make the decision based on the results you're getting, not on "common wisdom" aka "old wives tales."

If you're getting airbells then a short prewet may prevent them.

If you're getting uneven development, modify your agitation techniques.

If you don't have a problem, don't fix it.

-- John Hicks (jbh@magicnet.net), August 23, 2000.


One good reason for a pre-soak is to keep sheet film negatives from sticking to one another when developing them by hand in trays in batches. Anyone who has had the unpleasant experience of having two precious negs stick together in the developer knows what I mean. It can take an hour in the dark trying to soak them apart if it works at all. This, and avoiding air bells are the primary reasons why some photographers use a pre-soak. The differece is that it will add a little to your developing time. Some add 30 seconds or so to the time (or "ignore" the first 30 seconds of developing). Testing is better. In order not to have two developing times, one for the pre-soak, one for not, I simply pre-soak everything for one minute. If you are developing in tanks and have good, repeatable results and no air bell problems, you have no need of a pre-soak. Regards, ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), August 24, 2000.

I was under the impression the main reason to presoak is to remove the backside coating on most films. Some Kodak films have a heavy green antihalation coating. It seems to me to be a good idea to get rid of the stuff before it comes off in the developer, which it will certainly do. I don't care if it affects developing slightly or not, since I always do it and don't know the difference. I considering it as cleaning the loose layer off the film before processing.

-- E.L. (elperdido65@hotmail.com), August 24, 2000.

Do not pre-soak if you develop in Xtol.

-- Boris Krivoruk (boris_krivoruk@ams.com), August 25, 2000.


Presoaking was the recommended proceedure when films had thick emulsions. It swelled the emulsion and enabled the emulsion to soak up developer for more even development. I have tried both a presoak and no presoak and there is little difference other than getting the antihalation layer off the film. Try a presoak and see how much dye comes off after only one minute. I still normally use a presoak of 2-3 minutes for the same reasons photographers did with the older emulsions. Many photographers that I talk to, who I know do there own work, use a presoak for the same reasons I do. If you are getting good results then stay with your current methods. I use mainly sheet film and presoaking works for me. James

-- james (james_mickelson@hotmail.com), August 26, 2000.

I recently ran across a problem with pre-wet which has not been reported previously. I was measuring some characteristic curves for Agfa APX 100 developed in POTA. I found that both 5-minute and 1- minute pre-wets basically destroyed the negatives. The density was increased markedly in the higher density region, so that the overall contrast was substantially increased. The characteristic curves with and without pre-wet are shown in www.vsta.com/~alrob/prewet.html.

However, when I developed the same film in HC-110, there was absolutely no change in the characteristic curve with the prewet. I did some asking around, and I think that for most film/developer combinations, the pre-wet makes little or no change in the characteristic curve, and it probably does improve temperature control and even-ness of agitation.

I would suggest caution, however, when phenidone developers like POTA are used. Technidol is a prime example. Xtol has (apparently) a small amount of phenidone and should be checked. Jobo does not recommend a pre-wet with Xtol, and perhaps this is the reason.

-- Al Robinson (alrob@vsta.com), December 20, 2000.


Jobo does not recommend a prewet with Xtol because Kodak published rotary processing times WITHOUT a prewet.

Jobo found that in general a 5 minute prewet compensated for the difference between intermittant agitation in a small tank and continuous agitation in a rotary processor. It allowed them to make a general starting recommendation for any film/developer combination.

All of this is documented in back issues of the Jobo Quarterly, which you can buy, or read on line at the Jobo US site.

-- Terry Carraway (TCarraway@compuserve.com), December 21, 2000.


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