I am going to a regular custys house in morning, to remove cocnut oil, or the reidule she has left in

She spilt it a couple of weeks ago, and simply cleaned up with washing up liquid and water, great she thought it dissapeared , but now she has rang saying a black mark has appeared

.
I am guessing its a simple case of dirt been attracted to the remaining liquid, and therfore h/w/e will do the trick

However just to put my mind at ease, never dealing with coconut oil, has anybody come across cocnut oil before? and if so should i be thinking along different lines?
Apparently the oil she uses is something to do with dry scalp!!
geoff