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How much paper core dimensions change with humidity
Longer in summer, tighter in winterI put on weight in August too. I’ll tell you how many tenths.
🏆 Starting from the you found in the game.
Core delivered at 7% moisture, 12 mm wall. Rule of thumb: 1.0–1.5 mm per metre of length for each point of moisture.
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How the calculation works
A core does not keep its production moisture: it follows the warehouse air. In winter, heated air is dry, the core shrinks and cores go loose inside the roll; in summer, humid air makes it swell and lose radial strength, and the roll gets stuck on the shaft.
The changes per point of moisture are a rule of thumb widely used in the industry. On very wide machines, the length tolerance becomes the critical constraint.
Frequently asked questions
Why do cores go loose in winter and collapse in summer?
In winter, cold outside air heated indoors has low relative humidity: the core gives off water, shrinks and slips inside the roll. In summer, warm humid air makes the core absorb water and lose radial strength: the inside diameter closes up and the roll gets stuck on the shaft.
How should paper cores be stored?
Under cover, off the floor, ideally at 30% to 50% relative humidity, with stock rotation. Avoid long storage above 55% humidity, and avoid moving film-wrapped cores from warm to cold areas, which can cause condensation.
Sources
- ISO 11093-4 — measurement of core dimensions
- ROLL Lab calculation
The other lab apps
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📏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♻️Where your core goes at end of life
Tonnes per year, EWC codes, recycling route and a sheet for your plant.