Mark - would a gelatin based tintype work just the same as a collodion tintype?
yes they will work exactly the same except the developer is proprietary.
you coat the metal plate the same, except you don't soak it in a silver bath, its IN the emulsion
which is a silver nitrate, maybe iodide maybe bromide maybe chloride adn gelatin emulsion.
you don't need it to be wet when you use it, it is dry.
you fix it in normal fixer with hardener.
the fixer ( KCn ) isn't toxic, the media ( collodion ) isn't highly flammable/gives off toxic gas if it ignites.
the only downside is that the developer is proprietary so you have to buy it from the people that make it.
you can make your own emulsion ( lightfarm reference ) or buy a bottle of it from rockland colloid .
not sure where you are located but you might look at the rockland colloid website to learn more about their products
and if they are available where you are.
i've been making these tintypes for a few years now and coating with emulsion various things ( paper, glass and metal ) since 1986 ..
its fun
and dont' believe the hype that wet platters might suggest that dry plate tintypes aren't authentic, it is like daguerreotype users claiming wet plate
isn't authentic because it replaced daguerreotypes.
to see work done with dry plate tintypes you can google dry plate tintype or modern tintype or dry plate ferrotype you might find some ...
good luck !
john
ps you can cut a 4x5 plate in 1/4ers and put them in a 35mm camera to do tests to make sure everything is right
before you spend effort and $$ on a whole plate. with wet plate the wet is corrosive and you can't do that in a 35mm camera.