Materials
Materials3 min readUpdated
Corrugated board
Corrugated board is what shipping boxes, mailer boxes and pizza boxes are made of. Choosing it comes down to two things: how many wavy layers it has, and what paper is on the outside.
What is inside
Cut a box edge and look. Flat sheets, called liners, sit on each side of a wavy sheet, the flute. The waves stand like rows of tiny arches, so the board is stiff and hard to crush for how light it is.
The flute comes in sizes named by letters. Tall flutes, such as C and A, cushion and stack well. Small flutes, such as E and F, are thin and smooth, so they fold more neatly and print better. B sits in between. B and C are the everyday shipping boards. Flute profiles compares them one by one.
One wall or two
Board is described by how many flutes it stacks. Here is how the walls compare, with the thicknesses the editor's Board list uses.
| Construction | In the Board list | Choose it for |
|---|---|---|
| Single wall one flute, two liners | F 1.0, E 1.5, B 2.8, C 4.0, A 4.8 mm | Printed mailer boxes, retail and food boxes, most shipping |
| Double wall two flutes, three liners | E+E 3.0, E+B 4.3, B+C 6.8 mm | Heavy or large boxes, long trips, stacking |
| Triple wall three flutes, four liners | Not in the list | Very heavy loads and bulk transport |
There is also single faceSingle face One liner glued to one flute, with no second liner. Soft enough to roll round a product as a wrap.: one liner and one flute, soft enough to roll around a product as a wrap.
The same letter can measure a little differently from plant to plant. Treat the list as a starting point and ask your box maker for the real thickness. Which entries you see depends on the box: a tuck box stops at E fluteE flute A thin corrugated flute, 1.5 mm in our Board list. Flat enough to print well, it suits mailer boxes and retail packs., and a shipping box starts at F.
The paper on the outside
A board has two faces, and each gets its own liner. Which one faces out?
- Outside, the face people see: usually kraftlinerKraftliner A strong liner made from fresh kraft fibre, usually the outside face of corrugated board. Marked K in a board grade., made from fresh fibre. It is the strongest liner and the best to print on.
- Inside, against the product: often testlinerTestliner A liner made from recycled fibre, weaker and cheaper than kraftliner, often on the inside of a box. Marked T in a board grade., made from recycled fibre. It is weaker and costs less.
Need bright print? Ask for a white outer liner, bleached or with a white top layer. Corrugated liners compares the options.
On a brown liner, colours print darker and pale tints fade. Kraft paper and board explains what to expect and how a white underprint helps.
Reading a board grade
A box maker may write the board as outside liner, flute and inside liner, with each liner's weight in g/m². A K means kraftliner and a T means testliner. So 125K/B/125T is a 125 g kraftliner outside, a B flute and a 125 g testliner inside. This shorthand is common in the UK and Europe, and makers name their papers in their own ways.
US suppliers often rate a box by its edge crush testEdge crush test (ECT) How much load corrugated board takes on its edge before it crushes, as in 32 ECT. A US rating, for reference only. instead, such as 32 ECT for a common B flute mailer, or by burst strengthBurst strength How much pressure board takes before it bursts (the Mullen test). A US rating, for reference: it never changes a dieline.. Those figures are for reference: they describe how strong the board is, and they don't change your dieline.
On your dieline
A dieline needs one number from all this: the board's thickness. Your sizes run crease to crease and stay put. Where a wall folds back on itself, the thickness sets the gap between the two creases. On thicker board the slots between the flaps get wider too.
The drawing doesn't mark which way the flutes run. Your box maker sets that when they cut the sheet, so tell them if you have a preference.
Corrugated on your dieline
Pick the flute in the Board list, or type the thickness your box maker gives you. On thicker board the slots between the flaps get wider; your sizes stay the same.
- Cut
- Crease