Vallejo Model Color Metal Medium (Refractor or Interference Medium) produces an iridescent lustre caused by mica platelets coated with titanium dioxide which interfere with the reflection of light. When mixed with Model Color or Model Air, at 50 per cent of volume, it lightens the colour and gives them an iridescent shimmer. When used as final varnish it produces a silky effect. Mixed with other metal acrylics such as Model Color Gold, Silver, Bronze and so on it reduces colour intensity without diminishing the metallic shine.