The basics A slightly opaque, light viscosity, heavily pigmented blood. Used when pumping blood through small diameter tubing or when a rapid flowing blood is required.  The benefits Cleans up well with shaving cream or Ivory soap. The Look Bright - To suggest arterial bleeding or oxygen enriched blood, also for use on dark colored surfaces, or in low-light situations. Dark - To suggest vascular bleeding or oxygen depleted blood. Also for use on light colored surfaces. Extra Dark - Same color as our Drying Blood except that it does not dry. The Pro Tip To achieve optimum color, turn container up side down for several hours before use, then shake well. Pour directly into pumping apparatus. Used when pumping blood through small diameter tubing or when rapid flowing blood is required.