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What is kraft paper, and why is it strong?

7 minute read

Kraft paper is paper produced by the kraft process, a chemical pulping method that dissolves the lignin binding wood fibres together while leaving the cellulose fibres long and intact. Those long fibres are what make kraft noticeably stronger than paper made by mechanical pulping.

Kraft is a process, not a colour. That single fact clears up most of the confusion around the material. The brown you associate with kraft packaging is simply what the paper looks like when it is left unbleached, and kraft paper can just as easily be white.

Where the name comes from

Kraft is the German word for strength. The kraft process, also called sulfate pulping, cooks wood chips in a solution of sodium hydroxide and sodium sulfide. That dissolves lignin, the rigid polymer binding fibres together in wood, and separates the cellulose fibres with comparatively little damage.

Mechanical pulping, by contrast, grinds wood apart. It produces far more pulp per tonne of timber, but it shortens and damages the fibres. Newsprint is mechanical pulp, which is why it tears easily and yellows. Kraft keeps its fibres long, and fibre length is the single largest factor in paper strength.

Natural, bleached and white-top

TypeAppearanceTypical use
Natural kraftUnbleached warm brownMailers, cartons, shipping boxes, the default kraft look
Bleached kraftWhite throughoutWhere colour accuracy matters more than the kraft aesthetic
White-top kraftWhite printing face, brown reverseBright print outside, kraft inside, at lower cost than fully bleached

Bleaching costs strength as well as money. For most packaging the natural brown is both the cheaper and the stronger choice, which is a rare combination.

Kraft paper, kraft board and corrugated

These three get used interchangeably and should not be. They describe different things.

  • Kraft paper: a single ply, thin and flexible. Wrapping paper, void fill, the outer wrap of a rigid box, the face of a pouch.
  • Kraft paperboard: a thicker single ply, measured in points. 12pt through 24pt is the usual range for folding cartons.
  • Corrugated: a fluted layer glued between two kraft liners. The flute is what gives a shipping box its crush resistance.

So a folding carton is kraft paperboard, a mailer is corrugated with kraft liners, and both are commonly called kraft boxes. The distinction matters when you are comparing quotes, because a paperboard carton and a corrugated mailer of the same dimensions are not the same product or the same price.

What printing on kraft actually looks like

This is where expectations most often miss. Ink on natural kraft sits on a warm brown ground rather than a white one, and the substrate shows through. Every colour shifts: a red reads closer to brick, a blue closer to navy, and pastels lose most of their saturation.

Most brands choose kraft precisely for that muted, material quality. But if a colour has to hold exactly, there are two routes: print a white underbase beneath the colour, or use white-top liner. Both add cost per unit, and both should be decided at dieline stage rather than discovered at press.

Kraft also reads darker under retail lighting than it does on a backlit screen. For anything going onto a physical shelf, check a printed sample before committing to a run.

Recycling and composting

Uncoated kraft is among the most straightforward packaging materials to dispose of. It goes into the standard paper stream with no separation step, and its long fibres mean it can be repulped into new paper multiple times before they become too short to use.

What changes that is the finish rather than the paper. A gloss or matte lamination bonds plastic film to the fibre and takes the pack out of the paper stream. A PLA lining makes a food box commercially compostable but not recyclable. A foil laminate in a pouch rules out both.

In other words, kraft does not make a pack recyclable on its own. The specification does. We publish the disposal route for each finish so you can make the claim you are actually entitled to make.

When kraft is the wrong choice

  • Your brand depends on bright or pastel colour reproduction and the budget will not carry a white underbase
  • The product needs a high-gloss, coated retail finish to compete on its shelf
  • You need a moisture barrier and want the pack to stay recyclable, which is a genuine conflict rather than a solvable one

We would rather say so before a run than after. If kraft is wrong for your product we will tell you what to use instead.

Questions

Is kraft paper recyclable?

Uncoated and clay-coated kraft recycles in the standard paper stream with no separation step. Laminated cartons, PLA-lined food board and foil pouches do not. The finish decides it, not the paper.

Is kraft paper the same as cardboard?

No. Kraft describes how the pulp was made. Cardboard usually means corrugated, which is a fluted layer between two liners, and those liners are typically kraft. So most cardboard contains kraft, but kraft paper on its own is a single ply.

Why is kraft paper brown?

Because it is unbleached. The brown is residual lignin and the natural colour of the pulp. Bleaching it produces white kraft, at additional cost and with a small loss of strength.

Is kraft paper strong enough for shipping?

As a single ply, no. Shipping strength comes from corrugating it: gluing a fluted layer between two kraft liners. That structure, not the paper alone, is what resists crushing.

Send your dimensions

Pricing and a free structural dieline back within one business day. Keep the dieline whether or not you order.