While researching The Knowledge: How to Rebuild Our World from Scratch, Lewis Dartnell tried to get first-hand experience with many of the skills he discussed, like silver chemistry:
The mugshot included on the inside flap of the hardback book jacket was created using a primitive single-lens camera and this rudimentary silver chemistry, resurrecting techniques that date right back to the 1850s and the earliest years of photography.
Richard Jones helped enormously with this process. He’s the curator at the Fox Talbot Museum, in Lacock Abbey, Wiltshire, where the first photographic negative was created in 1835.
There are a few interesting things to note with this rudimentary photograph. Firstly, the primitive silver chemistry we used is very slow to react to light — it is hugely less photosensitive than modern ISO 400 films — and so correspondingly long exposures are needed. The image here is a 16 second exposure (hardly a snapshot!) and the slightest, imperceptible movement during that time results in a horribly blurred photo. To help solve this, hidden conveniently out of sight behind me is a wrought-iron stand and skull brace for holding my head perfectly stationary.
Such long exposures also mean that it is exceedingly hard to smile naturally, and hold the expression perfectly still for a good fraction of a minute without it looking like a rigour mortis snarl. This goes a long way to explaining the ridiculously-stern look common in early Victorian portraits of gentlemen and ladies. Believe it or not, this photo here is the most relaxed and natural-looking one we captured in a whole day of trying.
Also, the simple photochemical system used here is more sensitive to ultraviolet light than visible, as UV rays deliver more energy to drive the silver conversion reactions. This means that these photographs aren’t quite recording the world as the human eye sees it. As you can see, primitive photos make the lips look unusually pale (because they reflect more UV) and the skin appears more textured and blotchy in the UV.