@davidrevoy Here’s an adjusted version with a line erased into the eyes and aggressive smudging with the finger over the mouth (left is the normal pencil, right is the matte, I do not see a significant difference …) and three hash-tests: 12B, 6B, 2B, all three smudged for about 2 seconds with the finger (I only see smudging for the 12B, the others seem clean).
I rubbed the two sheets again, but still don’t see anything transfer to the other side.