õhukeseseinaline kärn, mille valmistamise põhimõte on sarnane koorikvormide valmistamise põhimõttega (vt kärn, koorikvorm), a hollow core made using a resin-coated sand that is blown into heated core machines; the cores cure and become rigid due to the reaction between the resin and heat (see: core, shell mold)