Silica gel is a great moisture absorber and has many different uses across lots of industries. From food to medicine to ammunition. But does silica gel expire and if so what is silica gel's expiration date?
It's an interesting question and if you plan on using your silica gel for a long them then it is one worth asking so you can make sure they continue to do what you need them to do.
Silica gel has no expiry date, it is effectively sand which obviously doesn't expire. However, over time they will absorb moisture and become less effective. You can put the silica gel packs in the oven in order to release the moisture and reuse them over and over.
I wanted to get a bit of a better understanding of what silica gel packets are made of and whether or not they expire. I also wanted to understand if they don't expire why not?
So I've done some research and I want to share it with you. You can also see my research on if gel ice packs expire.
What Is Silica Gel Made Of and Why Doesn't It Expire?
Silica gel is SiO2 and is effectively a synthetic microporous form of sand. It's non-toxic and shouldn't pose great harm to human unless coated with other dangerous substances.
It's made into beads and each of these beads contains thousands of microscopic cavities.
These tiny cavities create a low vapor pressure inside and this allows the silica gel beads to adsorb water molecules from the humid air which has a higher vapor pressure.
Over time water molecules get stuck in these microscopic pores of the gel. The silica gel adsorbs the moistures. This means the water gets attached to the surface of the silica gel.
This is different from absorption, where the liquid is dissolved into the solid.
This means that water sticks to the outside of silica gel but doesn't get absorbed by the silica gel.
This also means the process reversible. If you can find a way to remove the water from used silica gel beads then they will again begin to adsorb water from the surrounding environment.
This gives Silica Gel an incredibly long shelf life and allows them to be reused and reused over and over again without any real issues.
How To Reuse Silica Gel Packets: Recharge Your Desiccant
Silica gel packets can be “recharged” and then reused by removing the moisture from them.
Removing the moisture is simple
- Place the bags in the oven at 250°F (120°C)
- Leave for 12 hours
- Remove to cool
- They are ready to go!
While 12 hours seems like a long time to put something in the over for the below video experiment shows that you really do need to keep them in the oven for quite a long time if you want to remove the moisture.
20 minutes of a couple of hours won't remove the majority of the moisture.
Being left in the over for a longer period of time seems to do the trick.
Silica Gel Doesn't Expire
As you can see Silica Gel doesn't expire. It's basically sand that water attaches itself to. They can adsorb up to 40% of their weight in water.
By putting them in the oven you can remove the water allowing you to use them over and over and over again without issue.
You can continue to use them as long as you want.