Marie's Acrylic Retarder For Slow Drying Medium 180mlMarie's acrylic retarder 180ml. A retarder is a substance, usually added to water, used to slow the drying time of acrylic paints. Gives more time for blending or wet on wet techniques. Add just a little bit of retarder to paint or water. Brand: Marie's. Retarder is a water based product designed to slow down the drying time of acrylic paint. Acrylic paint with 15% retarder can prolong the drying time and make for better painting. The use of acrylic