A medium for increasing the "open" or working time of the Traditions paints and mediums.This medium is added to slow the drying of the paint. It can also be safely added to the other mediums in the line. Any time you want the paint or medium to have more working time add some Extender to it. Extender also allows the acrylic artist to perform oil techniques. This medium will completely evaporate when dry, leaving no solids behind. 3 fl. oz. bottle.