Sludge is a by-product of the acrylic paint manufacturing process. Sludge has the same handling qualities as regular acrylic paints and can be used as a paint, primer or paint medium. Recycled pigments also make great gesso! Tri-Art utilizes recaptured pigments from the manufacturing process to create a high-quality Gesso.
For more information and images please refer to: http://www.tri-art.ca/professional-acrylic-mediums.html