The most important process in any restoration of a painting on silk is the removal and replacement of the first backing. Unlike oil painting restoration, the taking-off and pastingon of the backing is a single continuous process. Before any work can be begun on the painting itself, special care must be taken in selecting the new backing paper. The color is especially important as it immediately affects the painting more significantly than almost any other aspect of the restoration. Though it is desirable to darken the backing paper in proportion to the natural aging and browning of the painting, other special effects can be created and much of the painting can be disguised by lightening or darkening the first backing. It is essential, therefore, to take all the possibilities of color tone into consideration, especially when working on important art pieces. Prior to the early 1950's, mounters placed their patches over holes from the back of the painting before laying down the first backing. In almost all such cases, however, the areas around the edges of the holes where the silk of the painting and that of the patch overlap were damaged. Today, overlapping of silk, whether in patching or backing, is avoided. The primary reason for this is because silk does not adhere well to itself, and suffers unnecessary abrasion in the natural contractions and expansions that every mounting incurs. Whether the paintings are framed or mounted as scrolls, patches are now cut to the exact shape of each hole and pasted on from the front of the rebacked painting. Ideally, this patching silk should be weaker than that of the painting. As old silk is no longer available, artificial means are used - most notably, electron radiation - to age new silk for patching. See also AATA 19-155.