A method for operating a printing group and to the use of a printing ink. The optical recording medium includes an L0 layer, an L1 layer, an L2 layer, and an L3 layer as the recording layers and first to third light transmitting spacer layers respectively arranged between the recording layers. The delivery system contains a pH-altering compound. A hollow portion is formed within at least the filter member. Ornamental attachments may be secured to the stepped base, to create a more aesthetically pleasing display of sushi or other food items.