Does Thermal Paste Expire in Tube? From Practical and Technical View Points

Maybe you just received that shipment of parts and are eager to put together your new build, or you think your computer’s running a little hot so you’re wanting to clean up. Either way, you reach for that tube of thermal paste that you used last year. But when you try to pump it out, it feels a little… hard? sticky? Not so… thermal paste-y…? But wait, you think, thermal paste can’t expire… can it? Well, let’s find out.

How to tell if thermal paste is expired

Practically speaking, “expiration” means a different thing for every substance. For apples, they rot. For chips, they become stiffer -- at least for the edible kind. For thermal paste, this expiration can be determined by looking at its viscosity. Generally, thermal paste should not be extremely sticky, should spread evenly, and come out of the tube easily.

So, if your thermal paste is hard to apply or spread, is very sticky, stiff, or hard to extrude… it might just be expired.

However, different brands use different formulae to create their thermal pastes, which results in different viscosities, hardness, and extrusion rates across the board. Some thermal pastes may exist in their original states as very thick and dry (though, we don’t recommend anyone use those). The most objective way to judge thermal paste is to look at viscosity.

Technically, if the viscosity of a thermal paste is twice its original state then the thermal paste can be considered expired. This is the best methodology that laptop brand owners and CPU manufacturers have come up with to gauge thermal paste expiry.

If it’s not yet clear, we don’t recommend using a thick and dry thermal paste.

What is the shelf life of unopened thermal paste?

Depending on the formula used, the average shelf life is between 6 and 24 months. That said, the environment where it’s stored can impact this. So, be wary of where you buy your thermal paste. If you’re buying from a physical outlet and the AC doesn’t work, chances are that your thermal paste is suffering on the shelf. Heat can accelerate the expiration of thermal paste. Extreme cold can also affect a thermal paste’s condition. So the perfect storage space is at normal room temperature without too much humidity. Think the way you would store a guitar.

How long does thermal paste last in an opened tube?

This again depends on the ingredients inside the thermal paste on the environment it’s stored in (store, warehouse, room, etc.). To get the most out of any opened syringe of thermal paste, make sure the open end of the syringe is sealed, and the tube itself is in a place that’s not too cold, hot, or humid.

So why the specific environmental conditions? Well, the major reason for a tube of thermal paste expiring when unused is that the organic solvent in the tube has been released into the atmosphere. This is why the thermal paste becomes dry.

Unlike other brands, Kooling Monster KOLD-01 employs no organic solvent, resulting in a longer shelf-life, both opened and unopened. Stored in viable conditions, an opened tube of KOLD-01 thermal paste can still be used even after months of storage.

How to properly store thermal paste?

As we previously discussed, the two most important things to consider when looking at the expiration of thermal paste are its ingredients and the environment it’s being stored in.

So what is the ideal environment?

The proper environment for storing thermal paste looks like this:

●       Room temperature (about 20°C/70°F, give or take)

●       Has good ambient humidity (about 40-50%)

●       Low light, preferably no direct sunlight

This can look like this:

●       A drawer in your room

●       A shelf in your basement

●       A hallway closet

If you’re a store or a warehouse, consider managing your humidity or light exposure.

Can thermal paste go bad on a CPU?

So far we’ve discussed thermal paste expiring on the shelf or after being opened, but what about when its been applied to a CPU?

The short answer is yes. Thermal paste expires on a CPU for the same reason it expires inside the tube: the organic solvent dissipates into the atmosphere, resulting in a decrease in viscosity, cracking, and powdering. This is much more noticeable on a CPU after some use than it is in a tube.

Unless you expose a tube of thermal paste to extreme heat like an oven or an open flame, chances are it’ll lose moisture slowly and you’ll only notice it if you open it after a few months or years. However, on a CPU the thermal paste will face regular exposures of 50°C/120°F, all the way up to temperatures of 80°C/175°F if you’re running stress-tests or working with less-than-ideal cooling.

That said, the constant cycles of high heat exposure will quickly cause the organic solvent to be released from the compound, resulting in the cracking and powdering mentioned earlier. That is also why it’s important to reapply thermal paste before it reaches that point.