Papers & Boards: Sources, Types & Properties
Where Paper and Board Come From
Paper and board begin as wood pulp — a slurry of cellulose fibres extracted from softwood trees such as pine and spruce. Timber is chipped, then either mechanically ground or chemically treated (the kraft process) to break the wood into individual fibres. Chemical pulping removes more lignin, producing a stronger, more durable sheet; mechanical pulping is cheaper but results in a weaker, more acidic paper that yellows over time. Alongside virgin wood pulp, the industry relies heavily on recycled fibre recovered from used newspapers, cardboard boxes and office paper. Recycled content reduces demand on forests and the energy needed to process raw timber.
Sustainable sourcing is increasingly important. The FSC (Forest Stewardship Council) certifies paper products whose raw materials come from forests managed to strict environmental, social and economic standards. FSC-certified paper guarantees that for every tree felled, replanting or natural regeneration takes place. Designers specifying paper for a product brief should always consider whether FSC certification is required by the client or demanded by the target market.
How Paper and Board Are Made
Pulp is mixed with large quantities of water to form a dilute slurry containing roughly 99% water. This slurry is sprayed onto a moving wire mesh (the Fourdrinier machine), where water drains through the mesh and the fibres begin to mat together. The wet web of fibres then passes through a series of press rollers that squeeze out more water, followed by heated drying cylinders that evaporate the remainder. The result is a continuous roll of paper. To make board, multiple plies of pulp are layered and pressed together while still wet, increasing thickness and rigidity. Coating with clay or chalk and calendering (pressing between smooth rollers) creates a smooth, printable surface.
Paper is measured in grams per square metre (GSM or g/m²). Below 170 g/m² is generally classed as paper; above 170 g/m² is classed as card or board. Typical photocopier paper is 80 g/m²; a cereal-box folding boxboard is around 280–350 g/m².
Common Papers and Their Uses
The paper family includes a wide range of specialist sheets, each engineered for a specific design or production purpose:
- Cartridge paper — a thick, slightly textured paper (120–150 g/m²) used for hand drawing, sketching and painting. Its surface tooth holds pencil, ink and watercolour well.
- Layout paper — lightweight and semi-transparent, allowing designers to trace and overlay ideas quickly during the initial design stages.
- Tracing paper — highly transparent, used to copy drawings precisely or to create overlays that show different layers of a design separately.
- Grid paper — pre-printed with squares, isometric dots or perspective grids to assist accurate technical drawing without specialist equipment.
- Bleed-proof paper — specially coated so marker pen ink does not spread beyond the drawn line, giving sharp, clean edges in rendered design visuals.
- Sugar paper — a rough, recycled-content paper available in a wide colour range, used for mounting, display work and craft activities.
Common Boards and Their Properties
Boards are stiffer, thicker and more rigid than papers. Each type is engineered for specific structural or commercial applications:
- Corrugated card — a sandwich structure with a fluted (wavy) inner layer between two flat liner sheets. The flutes act as columns, giving excellent compressive strength and cushioning, ideal for transit packaging and product boxes.
- Duplex board — a board with a bleached white top layer for printing and a grey recycled-fibre back. Used for food packaging, cereal boxes and cosmetics cartons where a high-quality printed surface is required at moderate cost.
- Solid white board (SWB) — made entirely from virgin bleached chemical pulp, giving a brilliant white surface on both sides. Higher-grade and more expensive than duplex board; used for premium packaging where colour accuracy is critical.
- Foil-lined board — a paper or board laminated to a thin aluminium foil layer on one side, providing a moisture and gas barrier. Used in food packaging (butter wrappers, confectionery cartons, coffee pouches) and drinks cartons.
- Foam board — a polystyrene foam core sandwiched between two sheets of smooth paper. Extremely lightweight yet rigid; used for architectural models, point-of-sale displays and exhibition graphics.
- Inkjet card — a smooth, coated card optimised for home or office inkjet printing, giving sharp colour reproduction. Common weight: 160–300 g/m².
- Mount board — a thick, acid-free board (approximately 1,400 microns) available in many colours, used to frame and display artwork or photographs without yellowing over time.
Paper weight in GSM (grams per square metre) measures mass, not physical thickness — a dense coated paper can be heavier in GSM yet thinner than a bulkier uncoated sheet of the same GSM. For board, physical thickness is often quoted in microns (micrometres, µm) — one micron is one thousandth of a millimetre. A standard cereal box folding boxboard is around 280–350 g/m² and approximately 400–500 microns thick. When a designer specifies board for a packaging brief, both figures may be relevant: GSM determines postage cost and stiffness calculations, while micron thickness determines whether the net will fit together at scored folds.
Callipers measure board thickness in microns. A micrometer screw gauge gives precise readings to 1–2 microns. In a workshop, a simple rule of thumb is that an uncoated board is about 1.4 microns thick for every 1 g/m² of weight, but this ratio shifts once clay coating is applied.
Physical and Working Properties
When selecting a paper or board, designers must consider several key properties. Stiffness (resistance to bending) increases with thickness and with the grain direction of the fibres — paper is stiffer along the grain, the direction in which the fibres lie. Porosity affects ink absorption; coated boards absorb less ink, giving sharper printed images. Opacity describes how much light passes through; a high-opacity sheet prevents text from showing through to the reverse side. Whiteness influences perceived print quality; a brighter white base improves colour vibrancy. Tear resistance is lowest along the grain — paper tears easily and in a straight line in the grain direction, and needs more force to tear across it. Tensile strength measures resistance to being pulled apart; kraft paper, used for paper bags and envelopes, has high tensile strength due to long chemical pulp fibres.
Paper fibres align in the machine direction (grain direction) during manufacture. Paper and board fold more cleanly, crease more crisply and are stiffer along the grain. When cutting nets for packaging, the grain direction should run parallel to the longest fold lines to prevent cracking and produce a neater carton.
Ecological and Social Footprint
Paper production has significant environmental impacts. Pulp mills consume large quantities of water (up to 10 litres per sheet of A4) and energy, and the chemical bleaching process produces chlorine-based by-products if elemental chlorine is used. Modern mills increasingly use totally chlorine-free (TCF) or elemental chlorine-free (ECF) bleaching to reduce toxic effluent. Deforestation is a key concern: illegal logging for paper pulp destroys biodiversity and releases stored carbon. FSC certification and recycled-content labelling allow consumers and designers to make informed choices. Socially, paper mills in developing countries have faced criticism for poor working conditions and displacement of indigenous forest communities — ethical procurement policies address this by requiring supplier audits.
Recycled fibre uses significantly less water and energy than virgin pulp, and diverts waste from landfill. Each time a fibre is recycled, however, it shortens slightly, reducing the strength and quality of the resulting sheet. Recycled board typically has a grey or brown appearance, which is why duplex board uses a white virgin-pulp surface layer over a recycled grey back. High-quality printing generally requires a proportion of virgin fibre to maintain brightness and smoothness.
The ideal solution for most packaging applications is a mixed-content board: recycled fibre for the structural core layers where strength per unit weight matters less, and virgin or de-inked pulp for the outer printing surface. This approach balances environmental performance against the technical requirements of modern printing and surface finishing.