Stacking Egg Cartons in Cold Storage

Published: 2026-11-11 | Author: Dragonegg Editorial

Why Cold Store Is Harder on Cartons

A cold store holds high relative humidity and cycles temperature at the door. Both push moisture into molded pulp, and moisture is what removes compression strength.

A carton that passes a laboratory compression test at 50 percent relative humidity can lose 30 to 40 percent of its strength after a week at 90 percent.

The stack does not fail at once. It creeps, the bottom layer deforms, and the pallet leans until the eggs at the corner crack.

Moisture Uptake and Strength Loss

Molded pulp reaches equilibrium with the surrounding air. At 90 percent relative humidity a carton can hold 12 to 15 percent moisture against 7 to 8 percent in a dry store.

Compression strength falls roughly 5 to 8 percent for each percentage point of moisture above 10 percent, which is why the cold store limit is much lower than the laboratory result.

Condensation cycles are worse than steady humidity, because liquid water enters the fibre faster than vapour and does not leave at the same rate.

Setting a Stack Height Limit

Take the compression strength measured at the cold store humidity, apply a safety factor of 2, and divide by the weight of one loaded carton.

That gives the maximum stack height. A carton rated for eight high in a dry store often limits to five or six in a cold store at 90 percent.

Add a margin for creep over the storage period. For storage longer than 30 days, reduce the calculated height by one layer.

The Pattern That Protects the Bottom Layer

Load should pass through the carton posts rather than the lid. A pattern that offsets the posts between layers puts load on the lid and doubles the deformation.

Align posts column to column, and use a slip sheet between layers if the pallet is built by hand. Misalignment is the most common cause of a leaning cold store stack.

Keep the bottom layer on a flat pallet. A damaged or bowed pallet deck concentrates load on two corners and starts the creep there.

Door Cycles and Airflow

Every door opening brings warm moist air into the store. The cartons nearest the door see more condensation cycles and lose strength faster than the middle of the room.

Position long-storage pallets away from doors and evaporator outlets. Direct airflow from an evaporator can dry one face and wet another, causing differential shrinkage.

If the layout cannot avoid the door zone, reduce stack height there by one layer and rotate stock more frequently.

Monitoring in Storage

Record temperature and humidity at three positions: near the door, mid-room and near the evaporator. A single sensor hides the variation that causes most failures.

Measure stack height at build and again at 30 days. A loss above 3 percent means the stack is creeping and should be re-stacked before it leans.

Keep a retained carton from the same lot outside the cold store as a reference. It shows how much of the change is moisture and how much is load.

A Practical Cold Store Specification

Specify compression at 90 percent relative humidity, a creep limit over 30 days, a maximum stack height for that humidity, and a post alignment requirement.

Add a door-zone rule: one layer lower within 3 metres of the door. That single line prevents most of the failures that appear as supplier quality complaints.

Review the specification when the store changes temperature setpoint or pallet type. Both change the load path and invalidate the previous height limit.

Questions Buyers Ask

How much strength does an egg carton lose in cold storage?

About 30 to 40 percent after a week at 90 percent relative humidity, because moisture content rises from 7 to 8 percent toward 12 to 15 percent.

How high can egg cartons be stacked in a cold store?

Take compression at the cold store humidity, apply a safety factor of 2, divide by the loaded carton weight, and reduce by one layer for storage beyond 30 days.

Why does post alignment matter?

Load should pass through the posts rather than the lid. Offset posts between layers put load on the lid, which doubles deformation and starts the stack leaning.

Are cartons near the door at higher risk?

Yes. Door cycles bring warm moist air, so those cartons see more condensation and lose strength faster. Reduce stack height by one layer within 3 metres of the door.

How is creep detected in storage?

Measure stack height at build and at 30 days. A loss above 3 percent means the stack is creeping and should be re-stacked before it leans.

Next Step

Send the store temperature and humidity, the carton count and the pallet type. You will receive a stack height limit for that condition and a pattern specification, in one reply.