It was a soaked layer, like the one you'll find with lith film. Anyone used it?
The one on lith film can be rubbed off real easy (with cold water from the tab), but on this film I needed hot (but not boiling) water.
No worries, the image didn't come off.
By the way, I did a pre-wash and the water coming out was green.
Here's an example (small file):