Edwal LPN and Kodak Photo-Flo

[Robert Kalman]

I'm thinking of mixing up some Rapid Film Dryer (as per Paul Lewis's formula in Steve Anchell's The Darkroom Cookbook) for those times when I need to rush a project along.

The formula is:
Isopropyl alcohol 30mL
Distilled water 970mL
Edwal's LPN 12 drops

Does anyone know if I can substitute Photo-Flo for the LPN?

[Mark Sampson]

Try it and see. Your issue will be to find the proper dilution of PF, some testing is in order.

[Pere Casals]

When mixing chem always things can happen...

Anyway Photo-Flo contains propylene glycol, so I guess that the isopropyl alcohol is to be compatible with the Photo-Flo wetting action without problems.

I tested "instant" drying with near pure isopropyl and it ends in a milky look in the negatives because of changes in the gelatin, this was used in the newspaper darkrooms when hurried. Those negatives can be perfectly printed, but that milk is not nice.

I guess that with the low isopropyl concentration you are to use you won't notice any milk, but if you have 35mm developed film ends (from the end of the cartidge) you can submerge those in different concentrations of isopropyl to recognize at what point you get the milky effect.

The 30ml/L isopropyl only shortens a bit the drying, to me the key points when needing a fast drying are:

> final distilled water bath with the Photo-Flo (as always)
> using an HEPA air (cheap) purifier in the room (as always)
> very carefully using a hair dryer

carefully is: starting the hair dryer before to clear any dust/particle inside, if you start the dryer while pointing the negative dust may end in the wet negative, the negative has to be correctly tensioned, using cold air first (at close distance) to remove drops on film, then moderate heat from far while all surface is wet, and then using cold air a bit closer until done. Whith a hair dryer one can destroy the negative, so one has to be careful... but in one or two minutes you have it.

Blowed air on negatives has an extensive record, it was used in the manufacturing, in the big processors and in the minilabs... but one has to be careful with it.


Of course you can always acquire or DIY a film dryer cabinet.

[Rick A]

Why so much LFN? The bottle calls for two drops per liter for normal use. I use about 5ml 91% isopropyl alcohol per 500ml with one drop LFN for final rinse, my negatives dry in a couple of hours. I'm not in a hurry to use them at that point, the emulsion may appear to be dry, but is still somewhat swollen and susceptible to damage. Back in the 60's and 70's I used to use product called "Yankee Instant Film Dryer" which did what it claimed, stunk to high heaven, but my 35mm negatives could be used within minutes of processing. That was great for meeting deadlines for certain projects, but not necessary now. For dust control, I keep a small electrostatic air cleaner running in my DR and just hang my film to dry.

[koraks]

Rapid drying works well if the film is squeegeed and then dried in a hot air flow. All resulting scratches and dust will of course add to the charm of a process that is rushed but preferably shouldn't be.

The alcohol/wetting agent/water mix may shorten drying times a little bit but not much.

A final bath of a high alcohol percentage will harden the gelatin further and may cause artefacts as Pere points out.

Perhaps consider using a normal final wash and allow for the 2-3 hours it takes to dry the film. If it needs to be quick, there's always di***al.

[Robert Kalman]

Many thanks for the insights, everyone. Very helpful!