Last year I was enjoying watching the participants of the Alchemists Workshop make tintypes and salt prints at the ANU School of Art, which they were doing after having their minds blown by the early photography collection of the National Gallery of Australia. The highly knowledgable and highly generous Craig Tuffin, and the intelligent and light hearted Lisa Clunie, agreed to help me in riffing off a carte de visite of the Melbourne spiritualist Dr Walter Lindsey Richardson and a kneeling spirit, taken by the spirit photographer Frederick Hudson in London in 1873-4, and now in the collection of the National Gallery of Australia. I have previously written about this very important carte de visite, and its reception back in Australia. And I kind of thought I sort of knew how Hudson had made it. But it is only when you are confronted with the task of creating a similar image, under similar conditions and using wet collodion emulsion, as Hudson did (although he used collodion on glass, not metal as we did) that you realize the complexity of detail and organisation which Hudson needed to command. If the exposure was made on one wet plate, and if Richardson was to remain unaware of the presence of the human model for the incarnate spirit, then, while Richardson was detained, perhaps with chatter from an accomplice, in the small waiting room of Hudson’s suburban backyard glasshouse studio, the spirit must have been exposed, but against some kind of moveable black screen. Then both spirit and screen must have been removed out of sight before Richardson was invited to enter the glasshouse. The alternative is a negative sandwich, but to me the similar sharpness of both Richardson and the spirit does not suggest a sandwich.