So I wrote to Remo:
Sorry to be a pest but I've got somebody who absolutely refuses to believe that Evans Hydraulic heads have oil in them but your two ply heads (Emperor and Pinstripes) do not. I can show him links to product descriptions, the physics of the interference patterns, discussions on drum forums. Nothing budges him. I don't want to cut into my Pinstripes and I don't even think that would do it if I had a video to show him. Can you please confirm that you don't have oil between the layers? If there is such a FAQ or entry in the forum then my search there came up with nothing.
and received this reply
Hello,Thanks for contacting us. We do not have oil in our pinstripes or any other drumhead we make. thanks! Brian LeVan - Global Sales & Product Support ManagerRemo Inc.