Another printmaking technique that involves using acid to etch into a metal plate. One creates an image on the plate by first covering the plate with an acid resist, or a ground, and then removing the ground in certain areas. In soft-ground etching, the ground is (as one might guess) soft, and can be removed to varying degrees. This allows one to make softer lines and to introduce a measure of tonality in what would otherwise be strictly a line drawing.
The most common method of creating a soft-ground etching is to first cover the plate with ground, and then place a piece of paper over the plate and draw onto the paper. The back of the paper will lift up the ground in accordance with the amount of pressure exerted in drawing. The resultant etch will tend to take on the characteristics of whatever one used to create the drawing: ballpoint pen lines will create very fine etched lines; charcoal or conte will make broader, softer lines. The ground will also tend to pick up the texture of the paper, so papers with a pronounced tooth or weave will leave the pattern of the weave on the final image. (Dragging your hand across the page as you are drawing will exaggerate the effect.)
The ground for soft-ground etching can either be purchased as is, or one can make it by combining powdered asphaltum, Vaseline and mineral spirits. The packaged soft-ground comes as a tin filled with a cake of hard brown wax-like material. One applies it by heating the plate and then running a palette knife with a clump of the ground on the end over the surface of the plate. The heat causes the ground to soften and melt, and one can then spread it out in a thin layer over the entire surface of the plate using a brayer. The hand-concocted soft-ground is a liquid (it is in fact often referred to as liquid soft-ground) which one can paint onto the plate directly.
See also: soft-ground texture.