Process for machining a flexible foam

A process for performing an operation on a workpiece comprising the steps of:

• a. providing a workpiece:
• b. hardening a portion of the workpiece, the portion being less than the whole workpiece;
• and
• c. subsequently to step (b) performing an operation on the hardened portion of the workpiece;
• wherein said step (b) is performed by spraying a liquefied gas from a nozzle onto the portion of the workpiece;
• wherein said step (c) is performed by using a tool to perform the operation on the hardened portion of the workpiece;
• wherein said steps (b) and (c) are performed by supporting the nozzle on the tool for movement;
• wherein said step (c) is performed by changing direction of the tool along the path, and wherein said step (b) is performed by moving the nozzle relative to the tool such that the position of the spray of liquefied gas can be changed relative to the tool when the tool changes direction.