Trouble cleaning Excelsior griddle

[GTurner]

I found a #7 Excelsior griddle in a local antique store last week. I'm having trouble completely removing whatever is still on there. There isn't any carbonization on the griddle. There appeared to just be light rust and dirt.

After I've cleaned with lye tank, scrubbing with steel wool and washing with Dawn, there was always a residue of what appears to be northern dirt (dark colored) on it everything time I would wipe it out.

I went to using a power tool (non scratching, I know I shouldn't) to try to remove the substance that is on there only to now have a black substance coming off when I wipe it off.

I placed it back in the lye tank to see if it is oil based. Hopefully it will clean up now. If not, what could cause this?

I know this was made between 1860 and early 1900's, but since it's not a skillet, I didn't think it would be this hard to clean. I also bought a Favorite #9 griddle at the same store. It cleaned up beautifully with little effort.

Thank you everyone. Enjoy your holidays.

 

[D_Madden]

did you try electrolysis?
I've had a couple of items that that were kind of unusual when cleaning up... one was a puritan wheat stick pan that I suspect someone soaked in vinegar for too long... and then they seasoned over the mess that they made... after electrolysis it just kind of smeared like the surface of the whole pan had a 'soft' layer on top of it.

 

[GTurner]

I'm in an apartment without a balcony. No place to have an electrolysis tank. I won't do it in my apartment because of the creation of oxygen and hydrogen gases.