Did a regular customer today,16th century house,open fire downstairs,on the landing I ended up taking the carpet (white man made fibre) off the grip rails,as when I started extracting near the edge with the hand tool it puled a load of black muck up,didn't help that there was a huge gap between the carpet and the wall,with no skirting board.
Tried the towel with some pog on it,but no difference.