In the headbox of a paper machine, the pulp slurry is more than 99.6% water, usually under 0.4% fiber; the headbox's job is to create turbulence that keeps fibers from clumping, which is called flocculation, and to spread the slurry evenly across the full width of the moving wire. The speed of the slurry jet compared with the speed of the wire matters. On fast machines the stock does not stay liquid on the wire long enough, so long fibers line up with the machine direction; this is why machine-made paper has a grain, and why strength differs along and across the sheet. At the couch roll, which is a hollow roll drilled with thousands of holes, a vacuum pulls water out of the sheet. By the couch, the sheet is about 25% fiber; it then goes to the press section, where it is squeezed between rolls and pressed against felts that absorb the water.

Yankee dryers make tissue soft. Tissue paper is dried on one big steam-heated cylinder with a hot air hood; the paper is sprayed with glue so it sticks to the cylinder, and a blade called a doctor blade scrapes it off, which crinkles it; this is called creping; a tissue machine can run at speeds of up to 2,000 meters a minute, about 75 miles an hour. Fillers and the size press help paper perform. Fillers such as clay, calcium carbonate and titanium dioxide improve opacity and printing quality. At a size press, the semi-dried sheet gets a thin layer of starch or other chemicals, reducing dusting and increasing stiffness; this is typical for printing and writing papers. Paper fibers wear out; each time paper is recycled the fibers are cut and weakened, and after being recycled four to six times, wood fibers become too short and weak to make paper; that is why mills mix fresh fiber, called virgin fiber, into recycled pulp for quality.

Bleaching costs fibers. Bleaching pulp to make white paper uses up about 5% of the fibers. Newsprint ranges from 55 to 75 on the ISO brightness scale, while writing and printer paper can be as bright as 104. The dandy roll, invented in 1826 by John Marshall, made watermarks easy to produce on a machine. It is a light roller covered in mesh embossed with a pattern; it presses the pattern into the wet sheet, thinning the fibers there, so that area passes more light. Wove paper, which has an even texture from a woven wire, is what machines usually make, while laid paper has faint ribbed lines. Handmade paper was formed on a mold with closely spaced wires, leaving laidlines, crossed by wider chainlines. Hand papermakers also get rough, feathery deckle edges.

Wood fiber is not the only fiber. Modern art papers made with cotton, linen, hemp, abaca, kozo and other fibers are valued for longer, stronger fibers and lower lignin content. Non-wood fibers account for about 5 to 10% of global pulp production, for reasons including seasonal availability and problems recovering chemicals. Central America had its own bark paper; the Maya used a writing material called huun starting from the 5th century and made codices out of it, and the Aztec form, amatl or amate, was used for writing, decorations, rituals and masks; some scholars do not consider Maya and Aztec bark paper to be true paper. The Battle of Talas story about how paper reached the Islamic world is not the whole story. Popular history says Tang papermakers were captured in 751 and gave up the secrets, but archives found in Panjikent date from before 722, and paper was made in Baghdad by the late 8th century.

A better recycling process helped save paper. In 1774 a German jurist, Justus Claproth, invented a way to remove printing ink from used paper, which is now called deinking; before wood pulp, old rag paper was recycled only into low-grade board. Recycling paper cuts pollution and trash, by one estimate; the U.S. EPA found that recycling causes 35% less water pollution and 74% less air pollution than making virgin paper; because paper fiber contains carbon that the tree took from the air, recycling also keeps that carbon locked up longer. Not everyone agrees how much energy recycling paper saves; the U.S. Energy Information Administration claimed a 40% reduction in energy when paper is recycled, while the Bureau of International Recycling claimed 64%. Kraft mills make much of their own energy by burning waste wood and black liquor, which is a reason the savings are debated. By one estimate as of November 2026, paper production accounts for about 35% of felled trees, though in most modern mills only 9 to 16% of pulp comes from pulp logs.

Words to know

• headbox: paper machine inlet
• virgin: new, unused
• flocculation: fiber clumping
• creping: crinkling tissue