Alphabe Thursday P is for Plumbago and pencil lead

I have recently learned that these days there is no lead in a pencil.  We understand that indeed real lead was used for drawing; Pliny says that it was used for ruling lines on the papyrus, so that the junior scribes would write neatly.  Later, in the 14th century Italian artists’ pencils were made by mixing lead and tin; any errors, apparently could be rubbed out with bread crusts.  

However, since the the 16th century, when discovered the the hills of the British Lake District, graphite has been used.  It is a relation to black carbon and called then plumbago, black lead or wad.  It was used mainly in ammunition casting.  A thin layer of plumbago round the inside of a cannon ball mould would allow the finished missile to pop out of the cast easily.   

It was much later in the 18th century when the oily stone was renamed graphite to be used for making marks on paper.