In the procedure described here, the cloth is wrapped over a model, the cloth is painted (IIRC from watching the show I saw, the idea is that the protruding parts get stroked more than the indented parts, not at all unlike when a private eye in the movies rubs a pencil over a sheet of paper in a notebook that was under one that a person of interest wrote something on), and then the cloth is baked, then washed.I've seen experiments where they recreated it just by painting on similar fabric, the results were identical.
http://www.cnn.com/2009/WORLD/europe/10/07/italy.turin.shroud/