•What is Silica gel? •Does it actually work? •Can they be reused?
•Why do I sometimes find them in cache containers?

Most of us would have come across Silica gel packs in one form or another, they commonly form part of the packaging for moisture sensitive items (Electrical items, bottom of the shoe box). Silica gel (made from sodium silicate) is in fact solid and not a gel as the name would suggest. It is a very good desiccant (drying agent) and will readily absorb moisture and reduce humidity. Silica gel itself looks like small glass beads and come pre-packaged and sealed in small packets.

Do they actually work?

We wanted to know how well Silica gel works and for how long it remains effective for. Two very simple tests were set up using film canisters and small strips of paper; The strips of paper were saturated with water to the point they became useless to write on and would easily break apart.

Each strip was placed in a film canister as follows:

Because we are using Indicating Silica gel we can be assured that the “New Silica” pack is unused. The control sample contained no gel, the “Used Silica” sample was a pack exposed to the air for some hours and the indicator shows the pack has been used. The three samples were then capped and left to do their thing for a few hours…

…The results were impressive, after only an hour or so, both containers with Silica gel contained dry strips of paper. Considering how wet the paper began, it felt 100% dry. We continued the test by wetting the paper again and repeating…

…A few hours later. The new Silica gel pack achieved a repeat result; The used Silica gel didn’t quite finish the job, the paper was dry and usable but slightly damp. These tests were extreme examples and demonstrates that for keeping moisture controlled in a sealed container they are extremely effective!

The tests do show that for continued effectiveness it is important to use new Silica gel , The problem with most Silica gel packs is knowing how much moisture has already been absorbed; If the pack hasn’t been kept in a air tight container then chances are it’s already exhausted most of it’s capacity. Indicating Silica gel is a great way of instantly knowing if a pack is new or used and is they type we use in our own cache containers, on our store and sold in individual packs [here...]

Indicator Silica Gel contains a percentage of coloured beads which change colour dependant on the moisture content. A new pack will be a deep blue colour indicating low moisture, the beads turn a pale (almost translucent) pink when the pack begins to absorb moisture. When the beads are pink it does not indicate the pack is exhausted, just that it has been used.

Throw away?

Most often it’s convenient to throw away used packs. In a well sealed container, a Silica gel pack should last several years, if not the lifetime of the cache. It is said that the packs can be restored by microwaving for 2minutes. Our tests showed this did appear to work (the indicator beads returned to their deep blue colour) but because the moisture is released into the microwave as steam, the packs tend to quickly re-absorb the moisture.

Cache Containers?

It’s become common practice to include a pack of Silica gel in cache containers to help protect the contents and log book. As above, it’s important to ensure the packs are new, those found around the home in the bottom of the draw or shoe box are unlikely to still be effective. moisture and dampness inside a container can cause mould and rust, can cause ink used in the log book to run and pages to stick. Most cache containers store the log book in a separate sealed bag to prevent disaster should the container let in water. Placing a Silica gel pack inside this bag and one or two inside the container itself is a the most effective use.

The Silica gel packs used in our tests are available from our store and included with all our cache containers containing standard paper log books.

Grab yourself a few packs today to help protect your own caches; They are also a great addition to a Geocaching cache repair kit. Any water damaged cache can be repaired and a few packs thrown in to help finish the job or stop further damage.