Although acrylics can be thinned with water, they lose quality in the process. Mediums can aid in the flow of acrylics without changing the hue or intensity of the color. In fact, acrylics can be heavily manipulated with the bevy of new mediums now on the market. Gels will thicken acrylics for an impasto effect, retarders slow drying time, and tinting mediums alter hue and/or color intensity.