Take 50 parts of luminous powder, prepared as previously directed, 4 parts bichromate of potash, and 4 of gelatine. These are to be thoroughly dried, and mixed by grinding. One part of the resulting powder is stirred with 2 parts of boiling water to a thickly fluid paint, one or two coats of which are applied with a brush to the paper or pasteboard to be made luminous. To avoid inequality in the thickness of the layer of paint the paper is passed through a sort of calender with rolls at a proper distance to insure a uniform spreading of the luminous mass. The rolls may be heated, if desired.