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Chapter 3: Using Timber
and heated. The resulting pulp is washed and bleached and pressed into mats. Further
processing of those mats of pulp eventually creates paper.
Once the pulp is made, it is passed into a machine to make the paper. The pulp is
sprayed into a thin layer on a moving wire screen. The screen is huge: it can be nearly
20 feet (6 meters) wide and moves at speeds of 60 miles (96.5 kilometers) per hour. The
water in the pulp drips off while it is on the moving screen, leaving behind a matted
sheet of damp cellulose fibers. This is then passed over rollers, which press it and dry it.
Logs destined for lumber are sent to the sawmill. Several different saws are at work
at a sawmill. A head rig saw is one of the saws. This one makes a rough cut of a log.
This helps ready the log for the different types of lumber it can become. The center-
most part of a log is oldest and may have more knots than other parts. This wood is
typically processed into heavy planks. The wood surrounding the center is younger
and less knotty. It may become the lumber found in a home improvement store.
A tree becomes lumber at a sawmill.