How can we manage "glass" interfaces which have a different volume (absorption) on each side of the interface. For example colored liquid within a colored glass.
I understand that to manage correct IOR we must configure the interface to have IOR= (IOR of medium normals away from)/(IOR of medium normals face towards)
However this does not solve the issue of needing to define a different volume for each side of the interface.
I tried mixing absorption shaders with backfacing as a factor but it does not appear to function. I'm guessing blender assumes when looking "out" of object there is only AIR so does not render volume when looking "out"(ie looking in the direction the normals face)