How does silica gel work?

Silica gel is porous silicon dioxide with an enormous internal surface area of about 700 to 800 square metres per gram. It adsorbs water vapour, physically holding it on that surface by Van der Waals forces, while staying solid. Its capacity is capped at roughly 25 to 40 percent of its weight when the pores are full.

Can silica gel be reused?

Yes. Silica gel can be regenerated by heating, typically to 120 to 150 C, to drive off the adsorbed water, after which it can be reused. This is unlike calcium chloride, which dissolves into a brine and is not regenerated.

Why does silica gel fail in shipping containers?

A shipping container's moisture load is measured in litres, and the high-humidity peaks of a long voyage exhaust silica gel's limited 25 to 40 percent capacity long before arrival. Once saturated it stops working while the dew-point cycle continues, so container rain forms. High-capacity calcium chloride is required instead.

Is silica gel safe and food-safe?

Food-grade silica gel is non-toxic and used in food and consumer packaging worldwide; the do-not-eat warning is to prevent choking, not because it is poisonous. Modern indicating grades are cobalt-chloride-free, avoiding the hazardous classification of older blue indicating gel.

Desiccant Technology

Silica Gel Desiccant

Silica gel is the desiccant everyone recognises, the little “do not eat” packets, and it is excellent in its place: small, low-to-moderate-humidity enclosures. But it is widely misapplied to jobs it cannot do, like keeping a 40-day container dry. Here is exactly how it works, its grades, how to regenerate it, where it wins, and where you need calcium chloride or clay instead.

Reviewed by the BENZ Packaging technical team · Updated June 2026

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How It Works

Adsorption on a Vast Internal Surface

Silica gel is amorphous silicon dioxide (SiO₂) processed into a rigid bead riddled with microscopic pores. Its power is surface area: a single gram has an internal surface of roughly 700 to 800 m². Water vapour molecules are adsorbed, physically held, onto this internal surface by Van der Waals forces. The gel stays solid and does not change chemically; it simply fills its pores with water. That gives it a clean, non-dusting, non-corrosive behaviour that suits small sealed packs, but it also caps its capacity: once the pores are full, at roughly 25 to 40% of its weight, it is saturated and adsorbs no more.

Silica gel performs best in the 30 to 70% RH mid-range and at moderate temperatures. It is ideal for protecting a camera, an instrument, a medication bottle or a small retail pack, anywhere the enclosure is small and the humidity load is modest. It is the wrong tool for a shipping container, where the moisture load is measured in litres and the high-humidity peaks of a long voyage exhaust its limited capacity long before arrival.

Silica Gel Grades & Forms

Not all silica gel is the same.

Non-Indicating (White)

Standard clear/white beads for general moisture control where a visual saturation indicator is not needed.

Indicating (Cobalt-Free)

Changes colour (e.g. orange to green) as it saturates. Modern grades are cobalt-chloride-free, avoiding the hazardous classification of old blue gel.

Food-Grade

Non-toxic, food-contact-compliant sachets for in-pack use with foods, supplements and consumer goods.

Sachets, Canisters & Bulk

From 0.5 g sachets to canisters and bulk, in Tyvek, paper or non-woven, sized to pack headspace.

Regenerable

Can be reactivated by heating (typically 120–150°C) to drive off adsorbed water and reused, unlike calcium chloride.

Inert & Non-Dusting

Chemically stable and clean, safe near most goods, though not nitrite-managed like clay for bare electronics.

When Silica Gel Is Right, and When It Is Not

Use the right desiccant for the enclosure.

Use silica gel for

Small sealed packs, instruments, optics, electronics boxes, medications, consumer goods, anywhere humidity is low-to-moderate and the volume is small.

Use calcium chloride for

Shipping containers and high-humidity, long-duration jobs, where you need 300–600% capacity to stop container rain. CaCl2 ›

Use activated clay for

Sealed barrier bags with bare metals, PCBs or pharma, where nitrite-free, solid-when-saturated chemistry is required. C DRY ›

Use molecular sieve for

Sealed applications needing an extremely dry endpoint at very low RH, such as insulating glass and gas drying.

Not Sure If Silica Gel Is Right? Ask Us

Send your enclosure, product and conditions and our team will confirm whether silica gel, calcium chloride or clay is the correct desiccant and specify the quantity, free, worldwide.

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Silica Gel Desiccant

Adsorption on a Vast Internal Surface

Silica Gel Grades & Forms

When Silica Gel Is Right, and When It Is Not

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Not Sure If Silica Gel Is Right? Ask Us