Pre-soaking negs

[Raven Garrow]

Thanks everybody for the response. What is wrong with being a dinasour???

[josh_560]

I process sheet film in trays and presoak not only to promote even development but to keep the damn film from sticking together-J

[Mark_437]

I believe the previous poster who mentioned "wetting agents" was correct - Ilford (and maybe others?) incorporate a wetting agent with their films. A way to pre-soak these films and not lose the benefits of the surfactant is to use the pre-soak water in the developer. While developing large film (12x20) in a tray, I do this by using a tip I got from Fred Newman (of Darkroom Innovations - now called The View Camera Store). I'm using D-76 at 1:1, and start by pre-soaking the film in 16 oz. of water (at normal dev. temp) for 4 min., then adding 16 oz. of D-76 directly to the water (giving me a dilution of 1:1) and starting the development timer at that point. It works great - smooth skies, no streaking of any kind, etc. I don't see why this method couldn't also be used in rotary tanks.

[Charlie Stracl]

I don't think anyone who frequents a "Large Format Photography" page would consider you a dinosaur for not wanting to give up silver based photography and darkroom work.

The only times I can recall getting airbells (air bubbles) on my negatives was when I didn't presoak, so I do it all the time, unless the process forbids it (like 2 bath development, where airbells are unlikely, anyhow).

I frequently do 2. I am sure this changes the development rate, but I've never had uneven development with it. It just changes the total time I need. A very short presoak is likely to give you uneven absorbtion of the water and uneven development. One to 3 minutes should prevent this, as it has for me.

[Al Robinson]

I recently decided to switch to rotary processing for my negatives. I decided to use the Jobo 2500 series tank for 120 and 4x5 negs. I was having nothing but trouble until I discovered that the 5 minute prewet suggested by Jobo was the problem. I just completed a test of Agfa APX 100 in 120 size, developed in POTA. I found that the prewet seiously distorts the characteristic curve, causing an increase in density at the higher densities, thus increasing the overall contrast by quite a bit. The curves with and without prewet fall on top of each other up to a density of about 0.4. After that, the prewet causes a growth of density which reaches 0.3 or so, and has the effect of producing a very peculiar curve shape. Without the prewet, the curve runs smooth and straight as can be. Of course, I have not tested every film and developer, but my belief is that the 5-minute prewet should be viewed with deep suspicion. I will be keeping you posted on my website www.vsta.com/~alrob on further research in this area.

Al Robinson