What is this scum in my coffee Hello, Lately my coffee seems to have a film on the top. The picture makes it look a lot worse then it is. It is more translucent in the cup. This happens once the coffee gets cold. When its hot it looks like bubbles or just the oil from the coffee beans.

What is this? Is this just the oil from the coffee? Or do I need to clean my machine?

Coffee Details:


Black Coffee, nothing added.
Made in espresso machine.
Ground to order.
Run through several times as I "overpacked" the coffee. 
Hot water added to make Americano. 
Beans from local roaster, last week.


This is what my coffee looks like before it turns into that:
It is just oil from the coffee beans. Nothing to be afraid of unless your coffee tastes off. You can stir the coffee to try and reincorporate the oil or use spoons to skim off the oil from the top