The massive use of air gaps in tooling, per the Evisto® concept, can confine the heat contributed by the cast alloy in a small volume. The resulting high die wall temperatures are turned to account to cast parts having ultra-thin walls, of the order of one millimetre thick. Effective thermal insulation limits thermal exchanges to slow the cooling of a cast alloy. The property that best characterizes this effectiveness is the reciprocal of thermal conductivity, thermal resistance. Air was chosen as the insulating material because of its many advantages: very favourable thermal conductivity, limited application cost, and zero purchase cost. Evisto®, an innovative tooling design, has been used to produce plates 1 mm thick measuring 130 by 200 mm and automobile seat backs 1.2 mm thick measuring 390 by 576 mm. The mechanical properties of the castings so produced complied with standard EN 1706 of May 2010 for aluminium alloy castings. A patent application was filed for the Evisto®concept in August 2010.