Kraft v Recycled paper used in box making
Kraft
The term “Kraft” relates to Liner paper made entirely from fibre (virgin fibre) direct from the tree source (pine tree) or Liner paper made with the outside surface consisting of virgin fibre and the inside surface being from recycled paper.
In Australia the most commonly used Kraft is the latter. The ratio of virgin fibre to recycled fibre varies and the manufacturers do not publicise the mix. Generally a 1:4 ratio is a guide – 25% virgin fibre and 75% recycled fibre is found in medium to light weight paper grades and 1:3 ratio in heavier grades – 33% virgin fibre and 66% recycled fibre.
The highest performing Kraft Liners are manufactured mostly from entirely virgin fibre.
The long fibres used to make Kraft Liner provide properties of high tear strength and high tensile strength, which makes this paper very suitable for use for rough handling, high humidity and in freezers and cool rooms.
Kraft Liner is used exclusively for dangerous goods boxes that require performance testing, for most fresh fruit and vegetable packs, most meat boxes and most heavy-duty packaging.
Kraft Liners are more resistant to moisture uptake than Recycled Liners and for many reasons, this is an important characteristic of paper used to make corrugated boxes.
Board made from Kraft Liners is known as Kraft Board and boxes made from Kraft Board are commonly referred to as Kraft Boxes.
Recycled Liner
No virgin fibre is used in recycled paper. The source is used paper, coming from many different sources. The fibres could be a mix of first recycling, through to the 6th or 7th recycling.
The process requires that the fibres are cut, so that progressive recycling causes the fibres to eventually become too short to be of use in the paper-making process, so the too-short fibres “drop out” of the mix.
For Recycled Liner to be relatively comparable in performance to Kraft Liner, the weight/mass (known as grammage) of the recycled paper needs to be about 10 to 15% heavier than the kraft paper.
In dry conditions, the short fibre in Recycled Liner provides high stacking strength and for many products, recycled paper is a very good choice.
In our world today we must recycle so we must use a high proportion of recycled paper, but to make the recycled paper we still need to cut trees down to make virgin fibre into Kraft Liner and to provide an ongoing supply of fibre for recycling.
Board made from Recycled Liners is known as Recycled Board and boxes made from Recycled Board are commonly referred to as Recycled Boxes.