Kraft and recycled papers are brown, grey or uneven to begin with. Box makers and brand owners still want a consistent, attractive shade – golden brown, deeper brown, or brand colours on liners. Basic dyes are usually the most economical way to get there.
Why basic dyes suit kraft
Unbleached and recycled fibres contain lignin and other anionic groups. Basic (cationic) dyes are strongly attracted to them, so they fix well, give strong colour at low dose and stay in the sheet.
Common shades
- Bismarck brown – the classic for evening out and deepening kraft brown.
- Auramine – bright yellow, used alone or to brighten browns.
- Rhodamine – pinks and reds.
- Methylene blue – blues and for adjusting tones.
- Malachite green – greens.
- Paper yellow for yellow papers.
Benefits
- High colour strength – small dose, big effect.
- Bright shades on unbleached fibre.
- Low cost per tonne of paper.
- Good affinity, so less dye in the white water.
Dosing and fixing tips
- Add dye to thick stock early so it mixes well before the headbox.
- Basic dyes fix best on unbleached fibre; on bleached pulp they may need a fixing agent or a switch to direct dyes.
- Keep alum and pH steady – changes shift the shade.
- Keep retention stable with a retention aid.
- Match against a master sample every shift.
Common issues
Shade varies with furnish
Recycled waste changes base colour. Adjust with small toning additions rather than big swings.
Coloured white water
Dye overdosed or poorly fixed. Cut dose, improve retention, or add a fixative.
Fading in sunlight
Basic dyes have moderate light-fastness. For long display life, consider pigment dyes.
Use cases
- Kraft paper and test liners.
- Corrugated box outer liners.
- Coloured envelopes and wrapping papers.
Need a consistent kraft shade? Send us a shade sample – we will suggest dyes and starting doses. Ask about dyes →