Not all desiccants are created equal. Choosing the wrong type — or the wrong quantity — for your container shipment can mean the difference between cargo arriving in perfect condition and filing a moisture damage claim. This guide walks you through the main desiccant types, how they compare, and how to match the right product to your shipment.
The Three Main Container Desiccant Types
Calcium Chloride (CaCl₂) — Best for Sea Freight
Calcium chloride is the highest-performance desiccant for container shipping. It absorbs moisture through a hygroscopic chemical reaction, converting water vapour into liquid brine which is retained in the desiccant's absorbent core. Calcium chloride desiccants can absorb 200–300% of their own weight in water — far more than any other commonly available type.
Best for: Long sea voyages (20+ days), trans-oceanic routes, moisture-sensitive cargo, humid origin or destination ports.
Available formats: Hanging bags (most common for container use), pole-mounted strips, bulk granules.
Silica Gel — Best for Packaging and Short Trips
Silica gel adsorbs moisture through physical attraction rather than chemical reaction, which means it becomes saturated relatively quickly. Absorption capacity is typically 30–40% of its own weight under standard conditions.
Best for: Air freight packaging, short-duration storage, enclosed product packaging.
Not recommended for: Long sea voyages in 20ft or 40ft containers — silica gel will saturate and stop working before the voyage ends.
Clay (Bentonite) — Limited Use Cases
Clay desiccants use natural montmorillonite clay, which absorbs moisture at moderate humidity levels. They're non-toxic and biodegradable. However, clay can release absorbed moisture if the surrounding temperature rises — the opposite of what you need in a container crossing warm climate zones.
Best for: Dry storage environments, short-duration needs, situations where non-toxic materials are mandatory.
Not recommended for: Tropical or trans-oceanic sea freight routes where temperatures fluctuate significantly.
How to Match Desiccant to Your Route
- Under 7 days: Silica gel or calcium chloride — 5–10 × 1 kg bags per 20ft container
- 7–20 days: Calcium chloride — 10–15 × 1 kg bags per 20ft container
- 20–35 days (Europe–Americas, Asia–Europe): Calcium chloride — 20 × 1 kg bags per 20ft container
- 35+ days (Asia–Ireland, Asia–Northern Europe): Calcium chloride — 20–30 × 1 kg bags per 20ft container
How to Match Desiccant to Your Cargo Type
- Agricultural products (coffee, cocoa, grain): Always use calcium chloride at maximum quantities. These products are highly hygroscopic and can accelerate moisture accumulation inside the container.
- Metal components and machinery: Calcium chloride. Even brief condensation exposure causes rust and corrosion on exposed steel.
- Electronics: Calcium chloride for the container; silica gel sachets inside the product packaging as a secondary measure.
- Textiles and leather: Calcium chloride. Mould develops quickly on organic materials exposed to elevated humidity.
- Pharmaceuticals: Calcium chloride for the container; molecular sieve desiccants inside individual packaging.
- Timber and wood products: Calcium chloride, plus ensure timber dunnage is kiln-dried to minimise its own moisture contribution.
The Hanging Bag Format: Why It Matters
For container use, hanging desiccant bags are significantly more effective than bags placed on top of cargo. Hanging exposes the desiccant to the maximum volume of air in the container, allowing it to adsorb moisture from the full container atmosphere rather than just the immediate vicinity of the bag.
Sorbpack's desiccant bags are supplied with integrated hooks for direct attachment to container lashing rings — no additional installation equipment required.
When More Is Better
When in doubt, use more desiccant. The cost of additional bags is negligible against the cost of a moisture damage claim. It is not possible to "over-desiccate" a container — excess capacity simply means the bags are not fully saturated at the end of the voyage, which is preferable to saturation mid-voyage.
Summary
For the vast majority of container sea freight applications, calcium chloride desiccants are the right choice. They outperform silica gel and clay by a significant margin on absorption capacity, and they're the only type capable of protecting cargo on long voyages across multiple climate zones.
Browse our container desiccant range or speak to our specialists for a shipment-specific recommendation.