From the manufacturer: This traditional organic sizing material is used oil painters to size their linen or cotton canvas prior to applying an oil ground. This size acts as a barrier to protect the fabric from deterioration from the oils in the primer. It can also be mixed with titanium white and precipitated chalk to create a dry gesso, which is an ideal surface for encaustic and egg tempera painting. Available as a dry granulated powder in re-sealable foil bags. 8 oz.