The value of graphite was soon realized, mainly because it could be used to line the moulds for cannonballs. 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 holder. 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. 