Page:The museum, (Jackson, Marget Talbot, 1917).djvu/140

114 paint in place. In this case, it is usual to place a thin tissue paper over the part that has been so treated until the mastic has thoroughly dried. A little cold water will easily remove the paper and the superfluous mastic.

Where a picture is in a serious condition, it is often necessary to re-back it. In the case of a painting on canvas this is rather a simple matter. A thin tissue paper or muslin is pasted to the front of the picture, the canvas is then taken off the stretcher and laid face down on a marble-topped table. The old canvas is carefully removed and the paint thoroughly wet with a rich mastic solution and a new canvas is carefully placed over this. In order to make the new canvas lie absolutely smooth, a warm iron is applied by some restorers. The process is a delicate one, as the new canvas must show no unevenness whatever yet the heat of the iron may do irreparable damage. When this operation has been completed, the new canvas bears the brunt of stretching over the new stretcher.

Where the painting is on panel, the process is a much more difficult one, as it usually entails the transfer of the painting onto canvas. Tissue paper or muslin is put upon the front of the painting as before. The virtue in this is that the paint is held in place by the tissue paper and no little