Sentence:  his quill drawings had a scratchiness , suggesting skin texture ; the <WSD>clay</WSD> he used plastically to suggest soft moving flesh , as in an abdomen , in a reclining torso ; the wax he smoothed over to give the body surface an elastic pull . 
Meaning of the word marked with <WSD> tags:  a very fine-grained soil that is plastic when moist but hard when fired