Photographic Film

Write the four requirements from the claim: transparent, insoluble in processing solutions, self-supporting and non-porous, flexible enough to roll. You will test all four.

Goodwin's base is nitrocellulose, closely related to guncotton. Nitrate film burns fiercely, needs no external oxygen, and destroyed archives and cinemas for decades. This blueprint casts a gelatin film instead. It meets three of the four requirements and fails the fourth in an instructive way.

Weigh 10 g gelatin powder.

Sprinkle into 60 ml cold water and leave 10 minutes until swollen.

Warm to about 50 °C, stirring until completely clear. Do not boil — boiling destroys the gel strength.

Pour onto a clean flat surface and spread to roughly 1 mm. Evenness is the whole craft — a thickness variation becomes a density variation in the picture.

Leave flat for 20 minutes to gel, then several hours to dry. Any vibration shows up as a ripple.

Peel the dried film and hold printed text behind it. Can you read through it? Record how clearly.

Roll the film around a dowel. Does it coil without cracking, and recover flat? This is Goodwin's “capable of being rolled upon the spools”.

Hold a strip by one end. Does it support its own weight, or flop? Compare a 1 mm strip with a thin one.

Drop a corner into warm water for two minutes. Gelatin softens and dissolves. Goodwin's claim demands insolubility in developing, fixing and intensifying solutions, and this is exactly why a wet-processed film cannot use plain gelatin as its base. Record what happened.

Now use gelatin correctly: cast a very thin gelatin layer onto your dried film and tint it with a drop of food colouring. Gelatin's real job in film is to carry the light-sensitive grains, not to be the support.

Measure thickness and cut a 35 mm wide strip. Punch sprocket notches along one edge. Compare with a real 35 mm frame if you have one.

US 610,861, “Photographic pellicle and process of producing same”, Hannibal Goodwin, filed 2 May 1887, granted 13 September 1898.

Goodwin was a rector, not a chemist. He wanted transparencies for Bible teaching, could not find suitable ones, and set out to make a flexible transparent support himself.

The eleven-year gap is the story. His original application was, by the assessment of the Science and Media Museum, broad, ambiguous and confused in its wording. It sat unissued and was amended repeatedly. In the meantime George Eastman and his chemist Henry Reichenbach entered the field, and by the time Goodwin's patent finally issued in 1898, Eastman had been selling celluloid roll film commercially for over nine years.

The Patent Office declared an interference — a formal contest of priority — between Goodwin and Kodak. Goodwin won. He then sued Kodak for infringement. He did not live to see the end of it: his estate was awarded roughly $5 million some years after his death.

Why nitrate film mattered and then had to go. Nitrocellulose gave the toughness and clarity the claim describes, and made roll film and cinema possible. It is also dangerously flammable and decomposes over time. “Safety film” on cellulose acetate replaced it, and a great deal of early cinema was lost to nitrate fires and decay before that changeover was complete.

Everything downstream of this patent — the roll, the sprocket, the cinema reel, and the colour films in this batch — depends on having a flexible base at all.