Hi all,

A question.

Imagine you're on a deserted island somewhere on planet earth.

You have no access to off-the-shelf photographic chemicals (nor to any industrially produced chemicals at all), including no access to your local drug store, diy store, supermarket or similar.

You *do* have some basic laboratory equipment, and can assume that any naturally occurring plants, animals or minerals that can be found anywhere on earth are also represented on your island.

You have an exposed role or two of generic b&w negative film and a small cave to use as a darkroom. How might you go about developing the film?

Any ideas anyone?

A trawl through Wikipedia suggests we might be able to obtain Catechol (a chemical commonly used for developing films) from fresh tea leaves. Apparently 25% of the dry weight of tea leaves is Catachin. We might then be able to heat the Catechol to make Pyrocatechol. But we're not chemists, so maybe this is all wrong.

Alternatives might include getting the Pyrocatechin direct from horse or human urine, or Pyrogallol (an alternative basic ingredient in photographic developer) by heating Gallic Acid derived from Gall Nuts, Sumac, Witch Hazel or other sources. But this process looks like it might require Sulfuric Acid and involve hydrolysis, which is where it all get's messy.

We'd then need an alkaline agent to mix with the Pyrocatechol to make the developer. Sodium Carbonate is often used, and Wikipedia suggests something like this might be obtained by burning dried seaweed, or from Borax, which would need to be mined. Either option sounds like it might be doable, at least in theory.

If we wanted to get snazzy we might be able to add some Sodium Sulphite (which helps the developer keep longer by delaying oxidation) made from the mineral Mirabilite, if we could find any on our island. And just possibly we might be able to make some Potassium Bromide (which helps suppress fogging on the film) through a reaction between iron ore and Bromine, although making the Bromine would be a whole project in itself so that might be an unreasonable goal.

For fixing we understand that plain seawater will provide a fix, given long enough, otherwise we'd need to explore making Sodium Theosulfate by (wikipedia again) heating Sodium Sulfite and Sulfur in water - the Sodium Sulfite derived (again, as above) from the Mirabilite and the Sulfur collected from the local hot spring. Umm, or something like that.

Do any *real* scientists out there have any better ideas? We'd really appreciate some input from somebody who actually knows about this sort of thing. All of the above is almost pure guesswork.

Many thanks for any suggestions.

Jeremy.