A process for forming a precision article by providing a thin sheet of material having front and back surfaces, placing the front surface of the thin sheet of material in contact with a surface of a mandrel, wherein the surface of the mandrel has a surface shape, and comprising the following steps: a) arranging an enclosure around a portion of the thin sheet and at least a portion of the mandrel to form a sealed interior , with a portion of the back surface of the thin sheet interfacing with an external environment ; b) forming at least a partial vacuum in the sealed interior to define a pressure differential between the sealed interior and the external environment , thereby causing the thin sheet to substantially conform to the mandrel surface to form a shaped thin sheet ; c) securing the back side of the thin sheet to a support structure to define the precision article; and d) removing the precision article from the mandrel , wherein the front surface of the shaped thin sheet defines the precision surface of the article, characterized in that the enclosure is made collapsible by a flexible or semi-flexible material that can support a vacuum within the sealed interior , and is made in the form of a collapsible vacuum bag around a portion of the thin sheet and at least a portion of the mandrel to form the sealed interior , with a portion of the back surface of the thin sheet interfacing with the external environment , and that the process is being carried out at a process temperature between room temperature of nominally 20° C and up to 70° C which is below the melting point temperature T P and the glass transition temperature T T of the material that makes up the thin sheet of which the front surface does define the precision surface of said precision article. a) arranging an enclosure around a portion of the thin sheet and at least a portion of the mandrel to form a sealed interior , with a portion of the back surface of the thin sheet interfacing with an external environment ; b) forming at least a partial vacuum in the sealed interior to define a pressure differential between the sealed interior and the external environment , thereby causing the thin sheet to substantially conform to the mandrel surface to form a shaped thin sheet ; c) securing the back side of the thin sheet to a support structure to define the precision article; and d) removing the precision article from the mandrel , wherein the front surface of the shaped thin sheet defines the precision surface of the article, characterized in that the enclosure is made collapsible by a flexible or semi-flexible material that can support a vacuum within the sealed interior , and is made in the form of a collapsible vacuum bag around a portion of the thin sheet and at least a portion of the mandrel to form the sealed interior , with a portion of the back surface of the thin sheet interfacing with the external environment , and that the process is being carried out at a process temperature between room temperature of nominally 20° C and up to 70° C which is below the melting point temperature T P and the glass transition temperature T T of the material that makes up the thin sheet of which the front surface does define the precision surface of said precision article. <EOS>