fortunately, a management buyout by joe katz put vellum and parchment works celbridge back in operation. vellum these days is normally supplied for orchestral tympani heads -sheets of the nature required for the book had to be painstakingly and rigorously prepared by hand -and then artists had to face the nightmare of working, one chance only, on an unfamiliar surface, a living material which stretched and shrank as it was wet or dry, a subtly uneven surface containing minute amounts of natural oils.