A Cautionary Tale - Water and removing gunk.

[steve B]

The cards that soak well, like T206s are almost always on coated stock.
The paper is a group of assorted fibers, with some sizing, which could be as simple as starch, or could be some other more adhesive like substance.

If having the colors come out brighter an a bit shiny is desirable, the paper is coated with a claylike substance on one or both sides.

If you've got water soluble stuff on the coated side, it will generally come off easily with water, as the hardened surface is sort of like pottery but thin enough to be flexible. If like many have it's developed microscopic cracks, fine gunk will soak into the fibers in the cracks and probably won't come out. (And to me it's both questionable AND way too much work to try.)

T206 backs are not coated, and it's much harder to remove gunk from the backs. *

As others have said, Goudeys are a sandwich of some pretty rough cardstock for the back and most of the card, with a layer of regular uncoated paper on the front. Gunk will be difficult to get off, and damage is almost guaranteed.

*The even better news is that I believe T206s are on a high rag content stock that's nearly acid free. Unlike many strip cards they'll probably be with us for a very long time.