The massive use of air gaps in tooling, per the Evisto® concept, can confine the heatcontributed by the cast alloy in a small volume. The resulting high die wall temperaturesare turned to account to cast parts having ultra-thin walls, of the order of onemillimetre thick. Effective thermal insulation limits thermal exchanges to slow thecooling of a cast alloy. The property that best characterizes this effectiveness is thereciprocal of thermal conductivity, thermal resistance. Air was chosen as the insulatingmaterial because of its many advantages: very favourable thermal conductivity, limitedapplication cost, and zero purchase cost. Evisto®, an innovative tooling design, hasbeen used to produce plates 1 mm thick measuring 130 by 200 mm and automobile seat backs1.2 mm thick measuring 390 by 576 mm. The mechanical properties of the castings soproduced complied with standard EN 1706 of May 2010 for aluminium alloy castings. A patentapplication was filed for the Evisto®concept in August 2010.