Flow Medium is a painting medium. It is used primarily to increase the viscosity of an artists acrylic paint. It is commonly used to create smoother blending effects which is not normally a characteristic of an acrylic paint, it can also be used as an overcoat to a previously dry painting to help the artist apply new layers.

Flow mediums vary among manufacturers, some will change the color of the paint until it is dry, some will increase the gloss of a paint, some will improve the thickness of a paint, and some will appear to water-down the paint increasing the transparency of semi-transparent colors. None of these characteristics are bade, it depends on your exact application, experiment with a few and see which one works for you.

For more information see: Painting Mediums, or the directory for Artists Paint Manufacturers.