The opposite of relief printing, the intaglio printing process uses copper or zinc plates as surface with incisions created by etching, engraving, drypoint, aquatint or mezzotint. This process exerts enormous pressure on the paper, pushing it into the deep recesses and fine lines of the metal plate. Therefore, a paper with exceptional strength and the ability to be dampened is required. (Dampening allows the paper to become softer and malleable enough to absorb the ink between the delicate incisions made into the plate surface.)
Each paper has its own optimal soaking time depending on the internal sizing, thickness and fiber content. Cotton papers with their long fibers need to be dampened or soaked longer than sulphite papers because wood fibers swell up faster. It’s interesting to note that the cotton fibers tend to maintain their shape when drying, fusing the embossed design into the paper much better than its wood fiber counterpart.