Don Widmer is a paper artist in Chicago. He creates pulp paintings on handmade paper, sculptural artist books, and letterpress prints. See more at his website: www.dwidmer.com
The hydrogen bond, which is necessary to create a strong sheet, needs water molecules present in both surfaces (meaning the base sheet and the pulp paint layer). Two problems might occur if you applied the pulp paint to a dry sheet: 1) the dry paper may seize up and wrinkle; 2) the pulp paint won't bond with the fibers in the base sheet and once dry, the pulp paint is more likely to flake off. The beauty of the pulp paint process is creating a sheet of paper with imagery built into the fiber of the sheet, a result of this natural chemical process.
Wet on wet, meaning the base sheet is freshly formed. This allows for hydrogen bonding to occur between the pulp in the base sheet and the pulp "paint". I usually apply the pulp paint within a couple hours of forming the base sheet, but I have left the base sheet sit overnight (kept covered and wet) before applying the pulp paint.
Thank you for your question. This is a generic name for a chemical product described as a resinous cationic liquid. On the Carriage House Paper website, they sell a product called Retention Agent. Looking at the specifications sheet for this product, the manufactured name is NALCO 9765. I have seen this product sold in both liquid and powdered form, from either Carriage House paper or Twinrocker Paper.
