MM24 Iridescent Medium is formulated to be mixed with the Matisse Structure or Flow Formula acrylic paints to add an iridescence (metallic sheen) to them.This medium can be mixed in any proportion with Matisse Colours.MM24 Iridescent Medium is based on pure iridescent pigment and contains no fillers or titanium dioxide; therefore the resultant mixes of iridescent colours are far more intense and richer in colour.Hint: The MM24 Iridescent Medium mixed with Matisse colours looks great over a black background.Available in 250ml and 1 Litre sizes.