Silica Gel Sachets: Best-Practice Guide
Silica gel used properly
How to protect your products with SECAL silica gel sachets. The golden rule: never leave the sachets — or the product — out in the open longer than you have to. Here is why, and how to do it right.
1. The golden rule: do not leave it in the open
Silica gel starts taking moisture out of the air the moment it is exposed. Every minute a sachet sits in the open — or the product stays uncovered — spends capacity that should have protected your goods inside the pack.
Sachets are opened and placed just before the pack is sealed. Whatever you are not using right now stays closed in its airtight bag.
15 minutes is the most a small sachet should spend exposed to the air; one hour for large sachets outside their sealed pack.
Why it matters: silica gel has a finite capacity. If it spends that capacity on warehouse air while it waits uncovered, it reaches the pack already partly saturated and protects far less. Silica gel does not expire with age — it is used up by exposure.
2. How it works: adsorption in a closed space
Silica gel is porous silicon dioxide. It captures water vapour by adsorption: water clings to the internal surface of the beads. That is why it only works properly inside a closed space, where it creates a dry microclimate.
Porous beads
Each bead has an enormous internal surface that traps water vapour.
Sealed space
Inside a closed box or bag it dries the air and keeps humidity low.
Equilibrium
It works until it saturates, or until the air in the pack is dry and stable.
Adsorption is not the same as absorption: the vapour clings to the surface of the bead rather than soaking into it. Silica gel takes up to 35–40% of its weight in water.
3. Step by step
In the warehouse — keep the stock sealed
Keep the sachets in their original airtight pack until the moment you use them. Store them somewhere cool and dry, on pallets, away from sunlight, open doors and damp walls. Avoid sharp temperature swings: they cause condensation that saturates the stock. Rotate first in, first out and note the receiving date.
Before packing — dry product, dry pack
Pack the product dry. Silica gel controls the humidity of the air; it does not dry a product that is already wet. Do not leave the product or the cartons uncovered for long before closing, and have barrier packaging ready — a bag or box that really closes. In an open pack, silica gel cannot do its job.
Placing the sachet — open, place, seal fast
Take out only the sachets for that batch. Put the sachet inside the pack and close it immediately; do not leave it in the open for more than 15 minutes for small sachets. The sachet must never touch liquid water — a splash or direct condensation saturates it at once. Never use a torn sachet: if it is losing beads, discard it.
Leftovers — reseal at once
Reseal unused sachets straight away in their airtight bag or a closed container. If the sachet has an indicator, use it to tell when it is saturated. Saturated silica can be reactivated with heat — an oven at 120–150 °C for 1–2 hours — where the sachet type allows it.
4. How much to use
The dose depends on the volume of the pack, on how well it closes, on how sensitive the product is, on the route and on the exposure time. A sachet that is too small for the space saturates in days instead of weeks.
Raise the dose if…
The pack has a weak barrier, the voyage is long, the destination is humid or tropical, the product is very moisture-sensitive (electronics, leather, metal), or there is a lot of air volume inside the pack.
You can lower it if…
The pack has a good barrier and closes tight, the route is short and dry, the product tolerates some humidity, or the pack is small with little air inside.
| Pack volume | Sachet size | Typical use |
|---|---|---|
| Jar, pill box or small bag | 0.5–2 g | Pill boxes, capsules, bags with garments, accessories |
| Small box or bag | 1–5 g | Small electronics, jewellery, samples |
| Medium box | 10–25 g | Footwear, spare parts, instruments |
| Large box or package | 50–100 g | Textiles, leather, small machinery |
| Large package or wrapped pallet | 250–500 g | Equipment, volume export |
Indicative table. SECAL supplies the 1 g, 2 g and 26 g formats as standard; other sizes are made up by combining sachets. The exact dose depends on the product, the pack and the route — confirm it with your SECAL adviser.
5. At a glance
Do this
- Stock kept sealed, cool and dry
- Product and pack dry before closing
- Open, place and seal quickly
- Leftovers resealed at once
- Dose set by pack, route and product
- Indicator used to tell when to change
Not this
- Sachets left open to the air
- Product and cartons uncovered for long
- Silica gel in a pack that does not close
- Torn or wet sachets
- Packing the product damp
- A sachet too small for the space
Mistake number one: leaving the sachets — or the product — exposed to the room before sealing. The silica spends its capacity on warehouse air and reaches the pack already tired.
6. Safe handling
Good practice
Keep the sachets out of reach of children and pets. Silica gel is inert and non-toxic, but it is not food: the “do not eat” wording is a choking warning. Use sachets made of a breathable, tear-resistant material that lets vapour through but holds the beads in.
Food contact
If you are packing food, use food-grade silica gel free of cobalt chloride. Do not reuse, in direct contact with food, sachets that have already been used in other applications.
7. Frequent questions
How long can I leave a sachet open?
As little as possible. As a reference, a small sachet should not spend more than 15 minutes exposed, and large sachets no more than an hour outside their sealed pack. It starts absorbing room moisture the moment it is uncovered.
Does silica gel expire?
As a material it is stable and barely expires. What runs out is its capacity: stored sealed it lasts almost indefinitely; left exposed it saturates before you use it. The key is the seal, not the age.
Will it dry a product that is already wet?
No. Silica gel controls the humidity of the air inside a closed pack; it does not dry a soaked product. Always pack the product dry.
Can I reuse the sachets?
Many types reactivate with heat — an oven at 120–150 °C for 1–2 hours — to drive off the moisture they captured. Single-use industrial sachets are not always worth reactivating. Never reuse torn, wet or contaminated sachets.
How do I know how much to put in?
It depends on the volume of the pack, how well it closes, how sensitive the product is and the route. A sachet that is too small saturates quickly. Use the table as a guide and confirm with your SECAL adviser.
What silica gel does your product need?
We help you pick the sachet size, the dose and the type for your pack, your product and your route.
This guide is a reference. Confirm product, dose and placement with your SECAL adviser according to your cargo and route. SECAL technical guides · PROTEXPO S.A.C. / SECAL, Lima, Peru.