The areas of 'shadows' are formed by multiple layers of washi paper, the more layers the less light gets through.
Shoko explained (through an interpreter) that Hemp was the original fibre for paper in Japan with Mulbery and rice comming later. She uses fine grade mulberry paper and rice (or starch) glue. The washi paper has very long fibers which makes it strong and difficult to tear against the grain. To tear against the grain first fold along the desired tear line and then lightly wet the fold, this will weaken the fibers and allow tearing. The characteristic long fibers mean that the paper can be layered with very little glue. Lightly beating the layers with the paste brush helps the glue penetrate the fibers of sucessive layers. It is the glue that gives her work its shine, the first layer has the shine and the last is more matt. Above is my sample from the workshop before drying.