How Does Silica Gel Work? A Simple Guide to Moisture Protection

Silica gel is a highly porous material that removes water vapour from the air. When placed inside a sealed or enclosed space, silica gel sachets help maintain a drier environment, reducing the risk of condensation, mould, mildew, rust, corrosion and musty odours.

You will often find small silica gel packets inside shoe boxes, electronics packaging and medicine containers. However, silica gel can also protect possessions kept in storage boxes, drawers, toolboxes, safes, camera cases, wardrobes, caravans and many other enclosed spaces.

What is silica gel?

Silica gel is a dry, granular form of silicon dioxide. Although it is called a “gel”, the finished material consists of hard, solid beads containing millions of microscopic pores.

These pores give silica gel an extremely large internal surface area. Water molecules in the surrounding air are attracted to this surface and held inside the pores.

Silica gel is therefore known as a desiccant: a material used to control moisture and humidity.

Does silica gel absorb moisture?

Silica gel is commonly described as absorbing moisture, but the technically correct term is adsorption.

An absorbent takes liquid into its structure, similar to a sponge. Silica gel attracts water vapour and holds it on the surface of its internal pores. This is adsorption.

In practical terms, the result is the same: the silica gel removes excess moisture from the air around the items you want to protect.

What do silica gel sachets do?

A silica gel sachet creates a drier micro-environment inside an enclosed space. This can help protect moisture-sensitive items against:

• Condensation
• Dampness
• Mould and mildew
• Rust and corrosion
• Musty odours
• Tarnishing
• Fogging of lenses
• Moisture-related deterioration

Silica gel does not repair existing water damage or remove a serious source of damp. Its purpose is to manage moisture vapour within a reasonably sealed area.

Where does silica gel work best?

Silica gel is most effective in a sealed or enclosed space because this limits the amount of new moisture entering from outside.

Good examples include:

• Plastic storage boxes with fitted lids
• Resealable bags
• Shoe boxes placed inside storage containers
• Camera and equipment cases
• Toolboxes
• Safes and document boxes
• Drawers and cupboards
• Product packaging
• Sealed display cases

Silica gel will become saturated much more quickly if it is left in a completely open room. It should not be considered a replacement for a room dehumidifier, ventilation or repairs to an underlying damp problem.

What can silica gel protect?

Clothing and textiles

Clothes, bedding and seasonal fabrics can develop musty smells when stored in humid conditions. Silica gel sachets can help control the moisture inside a sealed storage box or vacuum-storage bag.

The items should always be clean and completely dry before being placed into storage.

Shoes, trainers and leather goods

Silica gel can help manage residual moisture inside stored shoes, trainers, handbags and leather accessories. Place the sachet beside the item rather than forcing it into an area where the packet could tear.

Cameras and electronics

Cameras, lenses, cables and electronic components can be vulnerable to condensation and corrosion. Silica gel is particularly useful inside camera cases, equipment boxes and other enclosed protective packaging.

Tools and metal items

Excess humidity can encourage rust to form on hand tools, fixings and other metal components. Adding a suitable silica gel sachet to a closed toolbox helps maintain a drier environment.

Documents and collectables

Photographs, certificates, stamps, coins and other collectables can deteriorate when exposed to prolonged humidity. Silica gel can provide an additional layer of protection when these items are stored in suitable containers.

How quickly does silica gel work?

Silica gel begins attracting moisture as soon as it is exposed to the air.

How quickly it changes the conditions inside a container depends on:

• The amount of silica gel being used
• The size of the enclosed space
• The starting humidity
• How well the container is sealed
• The moisture already present in the stored items
• How often the container is opened
• The surrounding temperature and humidity

Using too little silica gel or placing it in a poorly sealed container will reduce its effective life.

How long do silica gel sachets last?

There is no single fixed lifespan for a silica gel sachet. It may remain useful for months in a well-sealed container containing dry items, but it can become saturated much more quickly in an open or consistently humid environment.

For long-term storage, inspect the contents periodically and replace or recharge the silica gel where appropriate.

Indicating silica gel provides a visible colour change as it collects moisture, making it easier to judge when reactivation or replacement may be needed.

Can silica gel be reused?

Some silica gel products are designed to be reactivated by controlled heating. This releases the water held within the beads so the silica gel can be used again.

Always follow the instructions supplied with the particular product. Sachet materials and recommended reactivation methods can differ, so not every packet should automatically be placed in an oven or microwave.

Once reactivated, allow the silica gel to cool and store it in an airtight container until it is needed.

Is silica gel safe?

Standard white silica gel is generally considered non-toxic, but the sachets must not be eaten. The packet and beads can present a choking hazard, particularly to young children and animals.

Always:

• Keep silica gel away from children and pets
• Leave the beads inside the intact sachet
• Do not use a damaged or leaking packet
• Follow any warning printed on the packaging
• Use only appropriately specified products near food or medicines

Choosing the right silica gel sachet

Silica gel sachets are available in different weights because a shoe box and a large storage container do not require the same amount of desiccant.

PREMIDRY offers sizes for everything from small packages and collectables to larger storage boxes, toolboxes, wardrobes and equipment cases.

Read our silica gel sachet size guide to find the most suitable starting point for your application.

Frequently asked questions

How does silica gel remove moisture?

Silica gel attracts water vapour from the surrounding air and holds the water molecules on the surface of its microscopic pores. This process is called adsorption.

Does silica gel prevent mould?

Silica gel can help reduce the risk of mould by controlling excess moisture inside a sealed container. It will not kill existing mould or solve an active leak or structural damp problem.

Does silica gel stop condensation?

It can help reduce condensation within an enclosed space by removing moisture vapour from the air. Results depend on the amount used, the quality of the seal and the surrounding conditions.

Can silica gel stop tools from rusting?

Silica gel can help protect tools by reducing humidity inside a closed toolbox or equipment case. Existing rust should be treated before the tools are placed into storage.

Should I open the silica gel sachet?

No. The sachet material allows moisture vapour to reach the silica gel while keeping the beads contained. Use the packet intact.

Can silica gel be used in an open room?

Silica gel is most effective in sealed or enclosed spaces. A room dehumidifier, ventilation or treatment of the moisture source is generally more appropriate for controlling humidity throughout an open room.