While I love to draw, I find that my ideas for sculpture germinate more fully when I sketch in 3D. So I will create a loose sculpture in clay (oil or ceramic) that captures what I am trying to portray. Sometimes I will make several of the same idea with different twists. In this way I can work out balance issues (so important in sculpture), clothing and nuances of gestures.
So - here is the "sketch" of Frederick Douglass. The finished fired piece is in the background. The fired portrait is 16" tall (clay shrinks as it dries and further shrinks when fired).
The sketch is 4.5" tall. It will likely be about 4" tall when dried and fired - make it roughly 1/5 scale to actual fired portrait.
I personally love to the loose, painterly look of sketches. Don't let the term sketch fool you into thinking not finished - it is, but in a more free and sometimes more artistically pure fashion as I don't overwork these pieces.
I will finish drying and firing this sculpture - and I will begin to offer a series of sketches for sale. It will be nice to offer original, finished sculptures for a low entry price point - I'll make an announcement when they become available. Each one will be an original. I may have several sculpts of the same individual due to the fact that I'm making small changes to find the right look - but each one will be a unique and separate work.