I guess they would qualify as tintypes, since it's a negative image on a black background, which makes it look like a positive.
Huge amount of chutzpah, some truly great images therein, and yay for the mad scientist ethos!
Using film since before it was hip.
"One of the most singular characters of the hyposulphites, is the property their solutions possess of dissolving muriate of silver and retaining it in considerable quantity in permanent solution" — Sir John Frederick William Herschel, "On the Hyposulphurous Acid and its Compounds." The Edinburgh Philosophical Journal, Vol. 1 (8 Jan. 1819): 8-29. p. 11