These days, pencils are produced on almost fully automated lines. The machines produce a row of pencils at a time from wooden slats. The main constituents of the lead are finely ground graphite, which is what makes the mark on the paper, and clay, which acts as a binding agent and gives the lead its shape and strength.
The two are blended in precisely defined proportions,depending on the hardness required. Then the soft mass is extruded through a nozzle to form long strings. These are cut to length, dried, fired in kilns, and immersed in a bath of oil to give a silky smooth “feel”. The tree trunks, which had been cut into little slats have to be seasoned for several months until they are completely dry and will not warp.
Then fine grooves are milled into the slats. The leads are laid in the grooves, glue is applied, a second slat laid on top, and the two pressed firmly together. When the glue has dried, a planing machine cuts each double slat into individual pencils. These must now be painted (the pencils receive several coats of paint), printed with the name and grade, in some cases dipped in paint, and finally sharpened.