DO NOT TRY THIS AT HOME. THIS WAS DONE BY AN UNTRAINED COLLECTOR AT 4:00 IN THE MORNING.


I acquired this card knowing it was in poor condition, but I didn't ask what the issue was as I was more concerned with just completing the set. I'm still not sure what the gunk on it was, but it looked like used motor oil, but felt dry and not sticky.
I chose to try our dish detergent to clean both the front and back surfaces, and no, I didn't soak it. I poured a generous splotch of Dawn on a paper towel and scrubbed the card vigorously. I figured the gunk was less likely to remain on the front and easier to clean as it is grooved which may have prevented seepage in theory at least.
After being dissatisfied with the results, I added a toothbrush to my scrubbing arsenal. It seemed to work better.


The front seems acceptable and an improvement over its previous condition, but the back still needs more treatment. However, I'll give it a rest before proceeding further. It has been quarantined from the rest of the set while being "restored". As with the dressing on a wound the card did receive a clean sleeve after the procedure.
“Aslan didn't tell Pole what would happen. He only told her what to do. That fellow will be the death of us once he's up, I shouldn't wonder. But that doesn't let us off following the signs.” - Puddleglum in The Silver Chair by C. S. Lewis