Yeah, it's kind of juvenile for sure, but I was amazed that this fairly esoteric process had it's own multimedia thingy.
You raise a good point though, we haven't really discussed the "taking" mechanism for this process at all. We've just taken for granted that we have 2 separations.
And to be honest, I don't know how they secured these seps! I believe that at some point, particularly with movie film, that they used a "duplitized" film stock, that is, 2 emulsions coated on either side of the film & appropriately sensitized. Then for processing, either side was floated on the appropriate dye bath.
But as for the big glass plates... anyone know?