Denny Anspach <danspach@...>
From painful personal experience (aching back, unholy brews of stinging salt and sweat running first into the eyes, then coursing down one's arms and legs; an atmosphere of stifling humidity promoted by salt's hydroscopic nature), I can attest to this is how much salt was routinely shipped: standard boxcars, usually SS or DS wood -but also wood reefers- that were at the ends of their lives. Wood cars lasted a relatively longer time in salt service. For steel cars, it was a short death march.
I cannot attest to whether or not "grain doors" (or similar) were ever used, but the salt cars that I had to deal with were simply filled with loose salt to either side of the doors. I also cannot attest as to how the cars were filled (in the '50s), but they were unloaded with coal scoops wielded by unhappy laborers from the very most bottom dregs of the pecking order.
Denny S. Anspach MD