Goods shipped in sea containers often spend weeks on routes that cross completely different climate zones. Along the way, a silent phenomenon can destroy them: condensation inside the container. Silica gel is one of the most widely used solutions to prevent it.
What "container rain" is
During a voyage, the temperature inside the container varies significantly — it heats up during the day, cools down at night, and the transition between a cold zone and a tropical one amplifies these swings. With each cycle, the warm, humid air inside the container releases moisture that condenses on the metal walls and ceiling. The droplets then fall onto the cargo — the phenomenon known as "container rain".
The result: mould, corrosion, detached labels, damaged packaging and compromised cargo. For a full container, the damage can mean significant financial losses.
How silica gel helps
Desiccant placed in the container adsorbs the moisture from the air, lowering the dew point and reducing the amount of water available for condensation. In effect, even if the temperature varies, there is no longer enough moisture in the air to form the "rain".
The quantity needed depends on the container size, voyage duration, climatic route and cargo type. For a quick estimate, use the sizing calculator, in "Shipping container" mode.
The factors that determine the quantity
- Container size — a 20 ft container typically needs fewer units than a 40 ft one.
- Voyage duration — long voyages involve more temperature cycles and more condensation risk.
- Climatic route — crossing between different climates (cold → tropical) intensifies the temperature swings.
- Cargo type — hygroscopic goods (wood, coffee, grains, paper, textiles) release their own moisture and need a larger dose.
Good loading practices
- Check the moisture of the cargo and packaging before loading — too high a water content "feeds" the condensation inside.
- Seal the container's ventilation openings, so the desiccant is not overloaded by outside air.
- Distribute the desiccant so that air circulates through it — moisture moves with the airflow.
- For valuable cargo or long voyages, combine silica gel in the individual packages with desiccant in the container space — two layers of protection.
Why the right choice matters
Too small a quantity leaves the cargo exposed; too large means unnecessary cost. That is why correct sizing — based on the actual voyage and the cargo type — is essential. The ChimGrup technical team can help you calculate the requirement and choose the right packaging.