In the case that you don't know what "soft ground" is, it's a intaglio printmaking technique.  By way of explanation, most etched lines are created by breaking through a "hard ground," I commonly use asphaltum mixed with turpentine.  When dry, that combination creates a solid resist that you break through using a stylus or other sharp object (I use a sewing needle held by a pin vise mostly).  The copper that is exposed etches away when the plate is immersed in an acid bath, and then you have marks on your plate.

"Soft ground," on the other hand, is a less solid resist that opens up the opportunity for much more subtle drawing.  The soft ground that I use is based on beeswax, which is melted and rolled out evenly with a brayer over the surface of the copper plate.  Once it's cooled, anything that makes an impression on the waxy resist will etch (literally anything, from errant fingerprints to the texture from cloth or paper and beyond).  Most of the time, I use soft ground as a means to add subtle shading to a print after I've already etched my linework.  In order to do that, you take a piece of tracing paper, place it over your plate with the soft ground already applied, and start drawing on the tracing paper.  Depending on the drawing implement you choose to use, you will get different textures.  In this instance, I did my drawing with a Col-Erase green pencil, which is a fairly soft lead.  That results in a more "pencil-like" line on the print.  If you wanted greater control and less obvious pencil strokes, you could use a harder lead and work harder at blending your shading.  However, I generally like to have my hand's work apparent, so I go with a softer lead than a lot of other people do.

Soft ground is a beautiful, subtle printmaking technique.  But unlike other processes, it can leave behind an artifact from the technique.  This drawing is one of those artifacts.

c.