"The value of graphite was soon realised to be enormous, mainly because it could be used to line the moulds for cannonballs, and the mines were taken over by the Crown and guarded. When sufficient stocks of graphite had been accumulated, the mines were flooded to prevent theft until more was required. Graphite had to be smuggled out for use in pencils. Because graphite is soft, it requires some form of case. Graphite sticks were at first wrapped in string or in sheepskin for stability. The news of the usefulness of these early pencils spread far and wide, attracting the attention of artists all over the known world". - From the excellent Wikpedia article on "Pencil".
We call it a pencil lead - but it's graphite = totally non toxic and a lubricant! - no wonder if flows
Like I said, over the last two years, a number of artists' comments on the foundational importance of drawing have stuck in my mind (often along the lines of "painting IS drawing") - and following Stapleton Kearn's observation that most people in his workshops had drawing problems, except for those who had done some sort of cast drawing., I've decided to spend a year on drawing. The good news is I've got right into it - the idea of shades of grey has gripped my imagination and will probably give me some "conceptual ideas" - but my basic premise is : YOU CAN TRAIN YOUR EYE. The two basic things - other than the exciting possibilites of the various drawing meda available - dynamic/flowing lines and etc. etc. is to limit meself to proportion and value - the two basics of a good representational image.