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Printing glossary: gsm, microns, ink and colour

Understand the terms used in paper and printer specifications, then continue with a practical guide.

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Paper weight (gsm)
The mass of one square metre of paper in grams. A 330 gsm paper weighs 330 g per m²; this does not tell you its exact thickness or stiffness. Also compare thickness and the limits of the paper path.
Thickness in µm
One micron (µm) is one thousandth of a millimetre: 375 µm = 0.375 mm. Thickness describes what must pass between the rollers. If the manual gives a limit in mm, compare values in the same unit.
Paper core
The middle layer between the two faces of a sheet. It contributes to opacity and handling. Black Core means a black middle layer, not a finish: matte and Luster can share a black core while having different surfaces.
Dye ink
An ink with colourants dissolved in the liquid. Some coatings are designed only for this type of ink. Check every cartridge: a printer can combine dye colour inks with a pigment black.
Pigment ink
An ink containing suspended coloured particles. Its behaviour depends on the coating. A pigment black requires a check when paper accepts dye ink only; selecting a media type called “photo paper” does not by itself resolve that uncertainty.
Compatibility status
A status compares the paper specifications with the printer’s published limits. A condition identifies the required tray or loading method. Missing or conflicting information remains uncertain; a specification-based status is not a physical test.
Sheet size
A4 measures 210 × 297 mm; A3 measures 297 × 420 mm. Document, sheet and driver sizes must match. Card capacity then depends on margins, bleed and cutting registration marks.
Accepted ink
The ink type the coating can receive, according to the paper specification. This concerns absorption and drying; it does not confirm that the sheet can feed through the printer. Check size, thickness and weight separately.
DPI and resolution
DPI describes dots per inch; for an image, pixels per inch links its pixel dimensions to its printed size. Enlarging a small image or changing its resolution number does not recreate missing detail. Check the PDF at its final size.
Bleed
Artwork extended beyond the cut line. It helps avoid a white edge when a cut shifts slightly. It does not change the final card size and must fit within the sheet’s margins and registration marks.
ICC profile
A file describing the colour behaviour of a device or a printer, ink and paper combination. A randomly selected profile does not ensure accurate colour. Only one stage should handle the colour conversion to avoid double correction.
Cutting registration marks
Printed marks a cutting machine’s sensor uses to locate the sheet. Their position and surrounding clear areas are part of the template. Moving or covering them, or scaling the PDF, can shift the entire cut.

4 practical guides