Paper and plastic cores and tubes · technical guide with sources
Paper cores and tubes: will your core hold the roll?
12 free calculators, ISO standards and guides with sources: to choose the right core, paper or plastic, and know where to ask for it. A ROLL Lab project.
The game · 5 steps · 90 seconds
The quest for the perfect core
Follow the map, light five torches and put your core to the test in the temple press. At the end you download its scroll, without leaving your email.
Choose by sight: what do you need the core for?
Tap the application closest to yours.
The lab: 12 calculators, results in seconds
Base: full result, free. Prof: free verdict straight away; the full report by email, only if you ask for it.
How much does your core weigh?
Weight per metre, weight per piece, pieces and metres per tonne.
base🔁Every unit, one language
Convert flat crush resistance between the units suppliers use.
base💧The sweating core
From warehouse humidity to lost strength: flat, radial, stiffness.
base🌡️Longer in summer, tighter in winter
How length and diameters change with humidity, season by season.
base📏Pass or fail?
Check the inside diameter against ISO 13542 tolerances.
prof🌀Will your core hold?
Radial duel: roll pressure against the radial strength of the core.
prof🧱How much wall do you really need?
From the strength you need to the minimum wall thickness.
base⚔️Paper or plastic? Let’s do the sums
Weight, strength, reuses and cost per use of 7 materials.
prof🚚How many cores in the truck?
Cores per pallet and per vehicle, with staggered rows and the container door.
prof🩺Why are your cores collapsing?
Dr. Core: the likely causes of crushed or loose winding cores.
prof🧪Paper or plastic? Three questions, one verdict
Environment, reuses and strength: which material pays off, and with what wall.
prof♻️Where your core goes at end of life
Tonnes per year, EWC codes, recycling route and a sheet for your plant.
Four numbers every core buyer should know
Sources: published industry studies, ISO 13542. Details in the guides.
What is a paper core?
A paper core is a cylinder made of strips of board wound in a spiral and glued ply on ply. At the centre of a roll or reel it carries film, paper, textiles, tape and metal strip through winding, transport and unwinding. You choose it by inside diameter, wall, radial and crush strength, moisture and tolerances (glossary).
This guide covers industrial cores for reels. Postal tubes for posters and drawings are close relatives: same technique, thinner walls, end caps and far simpler requirements.
The guides
Plastic cores
Reuse, hygiene, moisture and the PPWR: when plastic makes sense.
Core cutting
Saw, knife or lathe: dust, edge quality and tolerances down to ±0.1 mm.
How to choose a paper core
The 7 things to give your supplier, and the mistakes that cost you a roll.
Crush strength: flat and radial
Why the same flat crush can hide two very different cores.
Moisture: the variable that never stops
A core follows the air in the warehouse. Here is what that costs.
Sizes and tolerances
ISO 13542 standard diameters, ovality, how to measure.
The standards explained
ISO 11093 part by part, ISO 13542, CCTI T-108, T-158, T-159.
Core recycling
EWC codes, the PPWR and the end-of-roll problem.
Frequently asked questions
What is the flat crush of a paper core?
It is the resistance to flat crushing: a 100 mm sample is squeezed between two parallel plates until it first gives way. The standard is ISO 11093-9 (published in the UK as BS ISO 11093-9; in the US, CCTI T-108). The result is given in kN/m or N/100 mm. Read more
What is the difference between flat crush and radial crush?
Flat crush squeezes the core between two plates, along a line. Radial crush squeezes it with uniform pressure over the whole surface, as a wound film does, and is measured in bar (CCTI T-158 with steel balls, T-159 with an inflatable bladder). The two values correlate poorly: for film rolls, radial strength is what counts. Read more
What moisture content should a paper core have?
Usually between 6% and 8%. Below 4–5%, paper turns brittle, because the bonds between fibres need a little water; above 9–10%, strength drops fast. The humidity of the customer’s warehouse matters more than at production: the core reaches equilibrium with the air within days. Read more
What is the tolerance on the inside diameter?
Under ISO 13542 the tolerance is plus only: +0.5 mm up to 60 mm, +1.0 at 70, +1.2 at 76, +1.4 at 100, +1.6 at 120 and 150, +2.0 at 200, up to +3.0 at 300 and 400. The difference between two perpendicular diameters must not exceed 0.5 mm below 70 mm and 1.5 mm from 70 mm up. Read more
What do I need to give a supplier to order a paper core?
Seven things: inside diameter with tolerance, wall thickness (or outside diameter), length with tolerance, minimum strength with the test method (flat crush ISO 11093-9, radial crush CCTI T-158 or T-159), maximum moisture on delivery, edge and surface finish, and packing. Without the test method, a strength figure cannot be compared. Read more