It has come to my attention this past month that the dry tintype must be hardened befor development in the Dektol/thyocyanate developer.
Below you can find an exhample of what can happen without hardening. (.5 gm alum: to 1 oz. water. harden 1 min.)
Using developer D-19(dev 3 min) with cyanate requires no hardening but the plate is not as bright.