Key question
What properties define a paper, and how do you read them?
Paper consists of plant fibres, water, fillers and sizing. The alignment of the fibres and the density of the paper determine its stiffness, thickness, opacity and print quality. Technical data sheets summarise these properties into a few key parameters.
Learning objective: You can explain grammage, bulk, grain direction, opacity, paper shade, and surface finish, and calculate weight as well as spine width.
Paper has a grain and a weight.
2.1 / Fibres and grain direction
The fibre defines the character.
Four basic concepts describe the structure of a paper:
01
Fibres
Chemical pulp produces wood-free, age-resistant paper, whereas mechanical pulp yellows more quickly.
02
Direction of travel
In the paper machine, the fibres align; paper folds more easily parallel to this.
03
Grammage
Grammage in g/m²: An A4 sheet of 80 g/m² paper weighs around 5 grams.
04
Volume
Thickness-to-grammage ratio: for the same weight, high-bulk paper is thicker.
The grain direction is indicated on the data sheet as short grain (SG) or long grain (LG). For books and folded products, it should run parallel to the spine or fold, otherwise the fold will crack and the pages will cockle.
Always fold with the grain, never against it.
2.2 / Light, sound and surface
What the eye sees on paper.
Along with the structure, the optical properties are also important. Opacity indicates as a percentage how little a paper shows through. Whiteness and paper shade determine how bright images and colours appear, as well as the mood they convey.
The surface determines the feel and the print quality. Smooth, coated papers reproduce fine details sharply. Textured uncoated papers offer a tactile feel and absorb more ink.
01
Opacity
The higher the value, the less the reverse side shows through; important for double-sided printing.
02
Paper clay
Bright white, natural white or chamois: the paper tone influences every image and colour.
03
Surface
Smooth, matt, rough or textured: the surface defines the tactile feel and print sharpness.
White is not just white.
2.3 / Calculate weight and spine
A few grams can cost extra postage.
The weight is calculated by multiplying area by grammage: an A5 sheet measures around 0.031 m² and, at 120 gsm, weighs approximately 3.7 grams. For mailings, weight determines the postage, and for large print runs, it affects paper costs and transport.
You need the spine width for the cover and binding: number of sheets × grammage × bulk ÷ 1,000 gives the thickness in millimetres. Even so, ask your printer for a definitive value before designing the cover.
Calculate first, then design the envelope.
Exercise
Measure paper
Task: Determine the characteristics of three different papers.
STEP 1
Determine the grain direction for each paper using the bending or tear test.
STEP 2
Weigh one sheet of A4 paper and calculate: weight in grams × 16 = grammage (gsm).
STEP 3
Compare show-through, paper shade and surface side by side.
STEP 4
Record the results in a table with sample pieces.
Evaluation: Do your measurements match the datasheets? Where do they differ, and why?