Liquitex - Acrylic Effects Fluid Additive - Slow-Dri Fluid Retarder - 4 oz - Additives allow the artist to adjust the working properties of acrylic paint. They can be used to increase the flow, the opacity, or the thickness, and more. While they do contain acrylic polymer for compatibility, they do not contain sufficient acrylic resin to act as a binder within the paint. Liquitex Slow-Dri Fluid Retarder Fluid Additive is a fluid that slows the drying time of acrylic paints and mediums by up to 40%. An absolutely essential additive if working in drier climates. Mix into the paint when on the palette to slow the skinning-over of paint and increase blending time. Should not add more than 25% as there is no binder and it can weaken the stability of the paint film when too much is added.