Paper

Sizing: Sizing is applied to paper in the papermaking process to make sheets less porous. Without sizing, paper would react to moisture like a blotter. The type and amount of sizing applied to paper varies with each type based on the desired working properties. Drawing paper is sized for surface strength, helping protect the surface for erasing. Watercolor paper is sized to help produce a consistent wash as well as help the scrubbing and layering of colors.

"Strathmore does NOT use any animal products as part of the sizing process. The use plant-based and synthetic sizing"

and Yupo Paper: 100% polypropylene, suitable for watercolor and drawing.

Traditionally, vellum was made from the skin of calves, goats and lambs. Vellum has come to describe a high rag (cotton) paper, usually with a creamy white color and smooth surface comparable to traditional vellum. Today the term vellum is often describes a very clear translucent paper with a smooth surface.