Retouching And Varnishing. Ordinarily, the plate, well treated as I have just indicated, and especially when placed in the ten per cent, alum solution, may be readily retouched without using gum. If, however, the pencil should not take on certain portions, they should be lightly rubbed with a small tuft very slightly moistened with the liquid used for retouching varnish. The negative, well retouched, entirely finished, and perfectly dry, is varnished in the usual manner after slightly heating.