Blood, sweat and ink
We like a bit of experimentation with our inks and papers but we're pretty tame compared to some; cricketing legend Sachin Tendulkar had his blood mixed with paper pulp for a de luxe edition of his memoirs and scary Swedish rockers Watain use blood in ink to silkscreen posters. Kiss did something similar in 1977 when printing their first Marvel comic.
Further out there, the ashes of comic book writer Mark Gruenwald were (posthumously) added to ink in the printing of his work, and artist Wieki Somers uses a 3D printer to make sculptures from human ash.
Rest assured, Calverts uses 100% vegetable oil based inks made from soya or linseed and paper made from recycled pulp or certified from well-managed forests. We try to keep it simple, with few additives and no theatrics.