A method of chemical milling which includes the following steps: (I) suspending an extrusion or casting formed from metal in an etching solution wherein initially the extrusion or casting is fully submerged in the etching solution by virtue of its weight and which thereafter is rendered buoyant by metal being removed from the extrusion or casting by the etching solution wherein the casting or extrusion is supported by a non-buoyant support which maintains the casting or extrusion in a fully submerged condition throughout its immersion in the etching solution; and (ii) withdrawing the extrusion or casting from the etching solution when required.