T206 cleaning/soaking advice...
 

I've never tried "cleaning" my t2o6 cards. Purchased this Butler Sovereign portrait (arriving Tuesday 3/15) with the intentions of seeing what I might be able to do with the back. Seen a few posts and a youtube video or two, Wanted to see if there's any advice out there based on the cards current condition. Thanks in advance. I'll plan on posting the after pics as well.
-Ryan

looks to me like....
 

Not sure but based on the slightly faded inks on the back I would venture to guess this has already been cleaned and soaked and is not going to take much more abuse before its ruined. The black ink isnt going anywhere.... maybe some of the paper might come off in water but I bet its been tried already. Just a guess.....

Put it in a glass of water for a couple of days.

Since you sound new to this, DO NOT rub on the front of the card where paper is missing. You'll end up removing more of the surface paper.

The advice above seems sound. I suggest a two day soak, a rinse, and then blot dry it a few times, then put it between some paper and books (you don't want it pressed flat, you do want it to dry flat).

Patience. You can always soak it again. Gentle, you can't go putting paper and ink back on it.

I probably would not.
Likely already tried, and It is not going to change the "grade". May help the eye appeal , but could damage further. I like its current character :)

It's hard to tell until you have the card in hand, but the lighter word portions, like the 'BA' in "Base" and the 'S' in "Subjects," etc., may have thicker 'stains' obscuring them...or, like others have said, they may have been faded by previous efforts to clean. When you have determined which of those is the case, then you'll be able to move forward (or not move at all) more effectively.

I don't think the ink faded I think it's heavier residue in some areas.

I bought a T206 with similar soot on the back.

Cleaning it went poorly.

I would give it the penny sleeve/ toploader and check it off my list.

cleaning
 

I don't think this type of soot and other discoloration will soak off or clean off. I predict you will be disappointed if you try it.

I will echo the others on it. Those don't look like stains that are going to come off. Could be mildew...
.

Not sure if anyone has ever used this stuff, but it works great. It won't damage your card (well, I never had it happen. Always used a cheap stained card first to test it). I purchased many cards (50's, 60's and 70's) with stains, soaked them (individually) in a sealed-tight container for a bit, then once you open the container, you will see the liquid quickly evaporate on the card. Didn't always work (depending on what the stain is), but it most cases it did work.

Are we sure this is ink on the back? It looks more like mildew or black mold to me. If so, that's not going to come out with water. You'd probably have to use some harsh chemicals to get that out, and that would likely ruin the card.