Flashed glass is used for making photographic vignetting glasses, the colour being removed from the centre by rubbing with hydrofluoric acid. The operation is a messy one, however. Cardboard is by far the most convenient material to use for making vignettes, as a fresh one has generally to be cut for each negative. It is not necessary to keep a card vignette moving whilst the negative is printing. The usual plan is to shape the vignette according to the density of the different parts of the negative, to fix it at a greater or less distance from the negative, and, if necessary, to cover it with tissue paper. Many failures have been due no doubt to fixing the card too near the negative; it should be more than Jin. away, and should lap over where the negative is thin, for there the light will spread rapidly. Sometimes it is advisable to tuck a little cotton-wool under the vignette, giving a loose edge to the wool to avoid a hard line. To make a successful vignette by any method the background must be light; but vignetting is old-fashioned and seldom artistic, and should be avoided if possible.