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B&W Transparencies

Story location: Home / photography /
13/Sep/2002

There are a few black and white transparency kits available, ranging from buying pre-paid Agfa Scala to kits of chemicals designed for reversal processing ordinary black and white negative film to give slides. They all follow a similar processing method - develop the negative, dissolve the developed image, and develop the remaining silver halide to give a positive image.

If you don't want to mix the chemicals from scratch, or if you can't obtain any of the chemicals required, then it is possible to obtain B&W slides by other means:

  • Exposing Ilford XP2 at EI50-80 and developing in standard E6 transparency chemicals. This will give slides with a green cast.
  • Processing Kodachrome in E6 chemicals.
  • Exposing onto a duplicating film, eg. Eastman 5302

Reversal developing

The first stage is to develop the image on the film. The developer used here needs to give higher contrast than a normal film developer, otherwise the slide will look incredibly flat. The usual way is simply to use a print developer, with the addition of some sodium thiosulphate. Most print developers are suitable - I use Ilford Multigrade here because I also use it to develop my prints.
The next stage is the bleach/clear. This removes the developed image (which is a negative), so the remaining silver salts can then be re-exposed and developed to give a positive.

Developer

Ilford Multigrade 100ml

Sodium Thiosulphate* 25ml of 10% w/v solution

Water to: 500ml

*Approximate figure - optimum amount to be determined by experimentation. The effect of the thiosulphate is to lighten the developed image - it removes a small amount of density from the film so that the maximum density isn't too high but it also lightens the image.

Bleach & Clearing bath

There are two types bleach & clearing bath which may be used. The first is Potassium Dichromate/Sodium Sulphite, the second is Potassium Permanganate/Metabisulphite. Out of the two, the potassium permanganate option is less toxic, but can stain quite badly. Both will need to be handled with care.

1) Dichromate bleach/clear. The bleach and clearing bath solutions may be re-used. The bleach is exhausted when it changes from orange to green. The clearing bath starts off colourless and turns green after use; it is exhausted if it contains a hint or orange.
Bleach:

Water 500ml

Potassium Dichromate
CARE: Potassium Dichromate is toxic. 9.5g

Sulphuric acid 120ml of 10% vol. solution

Water to 1 litre

Clearing Bath

Sodium Sulphite 50g

Water to 1 litre

2) Permanganate bleach/clear. The bleach is prepared from 2 stock solutions because the acidified permanganate does not keep long, and needs to be prepared fresh.
Bleach:

Stock Solution A: Sulphuric acid 10% volume

Stock Solution B: Potassium Permanganate 4g/1 litre

Working strength bleach:

Stock A 500ml

Stock B 500ml

Clearing Bath:

Sodium or Potassium metabisulphite 25g

Water to 1 litre

Processing:

  1. First Development, 6½-7 minutes @ 20°C (re-use the developer for stage 8)
  2. Water rinse, 3 changes of water (instead of a stop bath)
  3. Bleach, 3 minutes (normal agitation - 4 inversions per minte)
  4. Water rinse, 15 seconds.
  5. Clearing Bath, 2 minutes (normal agitation)
  6. Water rinse, 2 minutes (several changes of water)
  7. Re-expose the film to light - at least 2 minutes under bright light. For best results, remove the film from the spiral (if there is sufficient illumination, and the spiral lets light get to the film, then the film may be left on the spiral).
  8. Second Development, 7 minutes @ 20°C (re-use developer from stage 1, then pour away)
  9. Water rinse, 15 seconds (just like a normal stop bath)
  10. Fix, 3-5 minutes (An acid-hardened fixer may be used to help protect the emulsion)

An alternative to re-exposure and re-development is to use a highly active developer to redevelop the remaining silver halide without any need to expose to light. One to try is:

Sodium Sulphite 50g

Hydroquinone 10g

Sodium Hydroxide 10g WEAR GLOVES AND GOGGLES!

Water to 1 litre

Leave out step 7, develop for about 10 minutes, then proceed to step 9.

Wash, 20-30 minutes as normal.

An alternative to continuous running water - using 3 changes of fresh water:
Pour in water, invert 5 times. Pour out.
Pour in water, invert 10 times, leave for 5 minutes. Pour out.
Pour in water, invert 10 times, leave for 5 minutes, invert 10 times, leave for 5 more minutes. Pour out.
Final rinse - 1 minute with distilled water or tap water with a wetting agent.

Duplicating film

Another way of producing B&W transparencies without having to buy extra chemicals is to use a film such as Eastman 5302 Fine grain release positive film. This is designed to give a positive image by having a negative 'exposed' onto it, in a similar way to producing a B&W print.

Making the exposure

The emulsion on Eastman 5302 is similar to a fixed grade paper - and is insensitive to red light, so it can be handled under a safelight. This means that it is possible to contact print a normal negative onto the film. Test 'prints' would be required to find the correct exposure in a similar manner to making normal contact prints.

Another way of exposing the film is by loading the film into a normal film cannister (the film is available in 100 foot rolls, so a bulk loader is necessary), and re-photographing the negative using a slide duplicator. This is the method which I use - the film speed needs to be set to about EI 6, and bracketed to get the best results.

Development

After exposing, the film can be loaded into a standard daylight tank and developed as normal. Any print developer should be acceptable, used at it's normal dilution. I use Ilford Multigrade for my standard darkroom work, so I tried this at the 1+9 dilution. Development times of 10-15 minutes produced acceptable contrast. It should also be possible to develop in a tray, but the lengthy times required mean that the darkroom would have to be free of any light leaks to avoid fogging the film. After development, stop, fix and wash as a normal film.

It is possible to tone the film, just like any normal B&W print. Monochrome transparencies can look a little flat when compared to colour slides, and toning can sometimes improve the final effect.

Back to Film Developers