Most buyers default to bleached pulp because absorbent products are white. That default is usually right — but not always, and the exceptions are worth knowing because unbleached grades can carry a meaningful cost advantage.
What bleaching actually changes
Bleaching removes residual lignin. It does not change fibre length, and it only mildly affects fibre strength. What it does change is surface chemistry and cost.
- Brightness: unbleached kraft sits around 25–35 ISO; bleached reaches 85–90 ISO.
- Strength: unbleached is generally 5–10% stronger because residual lignin adds stiffness to the fibre wall.
- Drainage: unbleached drains faster, which can be an advantage on high-speed lines.
- Cost: unbleached avoids the bleaching chemical cost and the associated yield loss.
When unbleached is the right answer
Three product categories can use unbleached or semi-bleached pulp without any consumer-visible downside:
- Industrial wipes and absorbent pads where the product is hidden inside packaging or equipment.
- Pet pads with a printed or coloured top sheet, where the core is never seen.
- Structural layers in a multi-layer core, where a white top layer covers a darker acquisition layer.
When you must stay bleached
Any product where the core is visible through a translucent top sheet needs bleached pulp. That covers most baby diapers, nearly all feminine hygiene products, and any white tissue or food-contact application.
There is also a hygiene perception factor. Even where an unbleached core is technically invisible, some brands will not accept it because a single consumer complaint about a “brown spot” costs more than the pulp saving.
The specification question that matters
Rather than asking “bleached or unbleached”, ask what brightness the finished product actually requires and work backwards. A semi-bleached grade at 70 ISO often satisfies the visual requirement at a lower cost than full bleach — and it is rarely offered unless you ask for it.