I made some once about 10 years ago and it was great fun. Used to do
these little chemistry demonstrations and used it in them. To make it I
nitrated some cotton wool (hey kids don't try this one) by refluxing with
conc nitric/conc sulphuric for a few hours. The gun cotton looked more or
less like cotton wool (just a slight sheen) but felt a bit stiffer. Went
up rather nicely when you held a match anywhere near it.
Collodion is a solution of this kind of stuff in alcohol (ethanol) and
ether (ethoxyethane). Ether is highly volatile, knocks you out and also
tends to catch fire at the slightest opportunity. Around 10 years ago you
could still buy collodion from a pharmacist - I haven't tried since.
However this was sold for dressing wounds and I am not sure if it is
suitable for photographic purposes. Together with a friend - Terry King -
I spent a day or two iodising it, trying to coat a plate, dipping it into
silver nitrate and exposing to produce a collodion negative from it
without success, but that may not have been the fault of the collodion.
We used a genuine wet-plate camera too, lent us for the occasion and
returned with interest - rather more silver stain on it. I think it was
worth about a couple of month's salary so I was glad we didn't break it.
A couple of years before this, a well-known UK photo-historian had
produced a film (sponsored by a well-known photographic company) in which
he demonstrated the wet plate process, apparently successfully. Meeting
someone concerned with the making of this film we tried to find out more
about how he did it, to be told he couldn't actually get it to work
either and the negative shown on the film was from a museum collection!