Fieldworkers also deal with the problem of preservation. A large portion of the audio cylinders made early in the twentieth century, for instance, have already turned to carbon dust, and no one knows how long information on audiotapes and videotapes will last. Audiotapes made in the 1960s often present problems today because the recording material has pulled away from the backing. And notes made with felt tip pens fade. The most lasting form of documentation is graphite pencil on acid free paper. Such paper is enor mously resistant to decay (it lasts centuries), and the graphite particles, imbed ded in the paper fiber, are not subject to fading or oxidation.