WHAT IT IS
Glass-like beads full of pores
Silica gel is a highly porous form of silicon dioxide. Its huge internal surface lets it absorb water and keep a small space dry.
Check your beadsStart
THE SCIENCE OF A SACHET
The little sachet
that drinks the damp.
It looks like sugar, but it is a sponge for water.
Silica gel is a porous form of silicon dioxide packed into sachets for shoes, pill bottles, cameras and snacks. Its tiny pores hold water vapour, and museums use the same material to keep display cases steady.
UP TO 40%of its own weight in water
Check your beadsKeep in mind
- Pores pull in water
- Colour shows when it is full
- Keep sachets from children
- A small packet with a big surface
THE SHORT ANSWER
A sponge for vapour,
not a seasoning.
Silica gel is usually non-toxic.
The warning is mostly about the packet itself.
WHERE IT GOES
Shoes, pills and cameras
Sachets protect medicines, shoes, clothing, electronics and some foods. Food-grade silica gel is safe for food storage.
Use it well
IN MUSEUMS
Steady air for old objects
In well-sealed display cases, conservators use silica gel to buffer humidity, absorbing moisture when the air is damp and releasing it when it is dry.
See the numbersA QUICK BEAD CHECK
What is in
your sachet?
Pick what you have found to see what US Poison Control says about it. The bar shows how much extra care the guidance suggests if it is swallowed.
Based on US Poison Control (poison.org). This is general information, not medical advice. In the UK, call NHS 111 if you are not sure whether something swallowed is harmful, or 999 in an emergency.
TWO NUMBERS WORTH KNOWING
Small beads,
large capacity.
One figure on how much it holds,
one on the indicator in blue beads.
40% of its weight
Water silica gel can absorb at high humidity
A US National Park Service exhibit note says silica gel can absorb up to 40% of its weight, held in surface pores and micro pores by capillary action.
CAPACITY · CONSERVATION WIKI
≤ 1%
Cobalt chloride in blue indicating gel
Poison Control says the cobalt chloride that turns blue gel pink is toxic, but the concentration is low, so a little blue gel is usually safe if swallowed by accident.
INDICATOR · POISON CONTROL
The same exhibit note says silica gel absorbs best below 25°C and works only in a tightly sealed space with air moving over it.
FOUR SENSIBLE HABITS
Keep the sachet,
mind the children.
Silica gel is useful to keep, and safe to handle sensibly. These habits come from poisons and conservation guidance.
Step 1
Store it out of reach
Keep medicines and products with silica gel packets up, away and out of sight of children.
Step 2
Check the pill bottle
Look carefully when taking medicine so you do not swallow the desiccant packet by mistake.
Step 3
Bin used packets safely
Throw away old sachets in a container children cannot get into.
Step 4
Seal the box
To protect photos or kit, put the gel in a tightly sealed container, not touching the objects.
WHY IT SAYS DO NOT EAT
A warning aimed
at the packet.
McGill University's Office for Science and Society points out that the sachets look like a salt or pepper packet, and US poison centres hear about hundreds of accidental swallows a year, mostly by children.
The gel itself is non-toxic and will most likely pass straight through. The warnings are there because a small child may try to swallow the whole packet, which is a choking hazard.
Questions
Questions on the way
What is silica gel made of?
Silicon dioxide in a highly porous form, sold as beads, granules or crystals. Its large internal surface lets it absorb water vapour and act as a drying agent, or desiccant.
Is silica gel poisonous?
US Poison Control says standard white or clear silica gel is not poisonous and swallowing it is considered a non-toxic ingestion. The packet can be a choking hazard for young children.
Why do some beads change colour?
Indicating gels are coated with a chemical that changes colour when the gel has absorbed moisture: blue cobalt chloride turns pink, and orange methyl violet gel turns green.
Can I use sachets to keep things dry?
Yes, they work best in a tightly sealed container with air moving over the gel. Conservators keep the gel from touching objects and avoid handling it with bare hands.
What should I do if someone swallows a lot?
In the UK, the NHS says to call 111 if you are not sure whether something swallowed is harmful, and 999 if someone is struggling to breathe, choking or unconscious.
Destination