Conventional foils are made by rolling mill reduction of a small billet down to a thinness of foil dimension. The research grades of foil made by Chromium Corporation are produced by electroforming a web that is started at zero thickness and grown to foil dimension. Through this approach, ultra thin foils are attainable. Some incipient weights are membranes with perceptible tensile strength so low that a copper support is required until they may be mounted upon utility apparatus. Even so, the foils display a remarkable ability to stand up to gas pressure differentials.
Commercial foils carry a thickness warranty.
Experience shows customary accuracy to be much better than the warranty limits. The Cleveland, Ohio plant is the center for all research foils.