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Material World
Material · Engineered

Paper

A mat of cellulose fibres bonded by hydrogen bonds alone — no adhesive, and where most harvested wood ends up.

Paper is a sheet of cellulose fibres held together by nothing but hydrogen bonds between the fibres themselves. No glue is involved: beaten cellulose fibres in water bond directly as the water is removed, and that is the entire mechanism.

It is also why paper fails the way it does. Wet paper loses almost all its strength immediately, because water breaks exactly the bonds holding it together, and any paper meant to survive wetting has a resin added specifically to provide bonds that water does not break.

Processing

Wood is reduced to pulp either mechanically, which is cheap and keeps the lignin, or chemically, which dissolves the lignin away with sodium hydroxide and sodium sulfide. The difference shows: mechanical pulp yields more paper per tree and yellows as its lignin oxidises, which is why newsprint browns and book paper does not.

The pulp is then beaten to fray the fibres, drained on a moving wire to form the sheet, pressed and dried. Fillers — usually ground calcite — improve opacity and printability, and calendering between rollers compresses the surface.

Uses

Packaging takes the largest share by mass and is growing as it replaces plastic; printing and writing papers are declining. Tissue is a substantial category of its own.

Paper is also a structural material in ways that go unnoticed: corrugated board gets its stiffness from geometry rather than material, and honeycomb paper cores are used in doors and lightweight panels.

Environmental impact

Paper is recycled at high rates and the fibres survive several cycles, shortening each time until they are too short to bond and leave the system as sludge. Recycling is therefore a cascade rather than a loop, and virgin fibre has to enter it continuously.

The industry's larger impacts are water and energy rather than the wood itself, since most pulpwood comes from managed plantation. Chemical pulping recovers and reuses its own chemicals and burns the dissolved lignin for energy, which makes a modern kraft mill closer to energy-neutral than its scale suggests.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

is sourced from

  • Wood — material · pulped mechanically or chemically; most harvested wood by mass ends here

contains

  • Carbon — element · as cellulose

is composed of

  • Calcite — mineral · ground calcite as a filler, for opacity and printability

is produced by

  • Kraft pulping — process · via pulp — most chemical pulp and therefore most quality paper

is used as

  • Packaging — application · cartons and cases, and the material most plastic packaging is now being asked to justify itself against

is an alternative to

  • Polyethylene — material · in packaging, where paper is winning back ground on recyclability and losing it on barrier — a paper wrapper that keeps water out generally has a polymer film on the inside, which is what makes it hard to recycle

Sources

  • Material World
    Our own writing

Questions this page answers

Where it comes from, and what it becomes

Follow Paper back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

  • Paper → is produced by (via pulp — most chemical pulp and therefore most quality paper) → Kraft pulping → takes as input (with sodium sulfide, breaks the lignin into fragments soluble in the alkaline liquor) → Sodium hydroxide → is produced by (at the cathode, in fixed proportion to the chlorine whether demand agrees or not) → Chlor-alkali electrolysis → takes as input (as the brine the cell electrolyses, and as the source of the hydrogen that comes off the cathode) → Water → is sourced from (by desalination, where energy is cheap and coastline available — the only route that adds fresh water rather than moving it) → Seawater
  • Paper → is composed of (ground calcite as a filler, for opacity and printability) → Calcite
  • Paper → is sourced from (pulped mechanically or chemically; most harvested wood by mass ends here) → Wood
  • Paper → is produced by (via pulp — most chemical pulp and therefore most quality paper) → Kraft pulping → takes as input (and the pulp and paper industry is among the largest industrial water users there is) → Water → is sourced from (by desalination, where energy is cheap and coastline available — the only route that adds fresh water rather than moving it) → Seawater
  • Paper → is produced by (via pulp — most chemical pulp and therefore most quality paper) → Kraft pulping → takes as input (as chips, cooked until the lignin dissolves and the cellulose fibres separate) → Wood
  • Paper → is produced by (via pulp — most chemical pulp and therefore most quality paper) → Kraft pulping → takes as input (with sodium sulfide, breaks the lignin into fragments soluble in the alkaline liquor) → Sodium hydroxide → is sourced from (electrolysis of brine, which produces chlorine in fixed proportion) → Halite

These are the most distinct paths back. Paper can be traced through others besides.

Downstream — what it becomes

  • Paper → is used as (cartons and cases, and the material most plastic packaging is now being asked to justify itself against) → Packaging