Modern thermal paste does not need a cure or burn-in period. Pastes such as ARCTIC MX-4 are not described by their maker as needing one, and a published review that rechecked MX-4 after 48 hours found no change. A small group of older pastes, Arctic Silver 5 being the usual example, do specify roughly 200 hours of use for a small gain. If temperatures look wrong right after a fresh install, the cause is usually mounting or paste application, not waiting.
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Quick Answer
- Burn-in is not required for mainstream non-curing pastes. ARCTIC’s MX-4 page and its support FAQ list no burn-in step, and Thermal Grizzly’s FAQ lists none for Kryonaut either.
- When it is real, the effect is small: community sources put the difference between fresh and fully cured Arctic Silver 5 at roughly 0.2 to 3 degrees Celsius.
- Small early settling is normal. Paste can spread and fill microscopic gaps over several heat-and-cool cycles, which is different from a chemical cure.
- Judge fairly: compare at the same room temperature, fan curve and workload, and look again after a day or two of normal use.
- Reseat if temperatures are far worse than before, one core runs much hotter than its neighbors, or the system throttles at once. Waiting will not fix a bad mount.
What You Need
- The paste you plan to use, and a way to clean the old one: isopropyl alcohol with lint-free wipes, or a dedicated cleaner. ARCTIC recommends its MX Cleaner for residue-free removal.
- Your cooler’s mounting hardware and the correct screwdriver, plus the motherboard manual if the mount is unfamiliar.
- Monitoring software that shows CPU temperature, clock speed, power and fan speed together.
- A repeatable load, such as a ten-minute stress run or the same game scene, so before-and-after numbers are comparable.
- A note of room temperature for each run. A few degrees of room change can hide a paste effect.
Is Curing Real?
Some thermal compounds contain materials that set or settle over time, and those can show gradual improvement. The best-known case is Arctic Silver 5, which community sources say wants around 200 hours of use and repeated thermal cycles, with the gain between a fresh and a fully cured application typically 0.2 to 3 degrees Celsius. Even in that case, the effect is small, and many builders skip such pastes for convenience.
Most current pastes are different. ARCTIC states that MX-4 is metal-free, not electrically conductive, with a viscosity of 31,600 poise and a density of 2.50 grams per cubic centimeter, and describes it as non-drying and non-bleeding. Its continuous-use range is listed as minus 50 to 150 degrees Celsius. None of that includes a break-in requirement. A Vortez review measured MX-4 again after 48 hours and saw no change in performance, while the same test showed Arctic Silver 5 improving.
You will still find forum posts reporting a few degrees of improvement after a day or so. One user described idle temperatures falling from 32 to 27 degrees Celsius over about ten hours. Anecdotes like that cannot separate paste from room temperature, background tasks and fan curve changes, which is why a controlled comparison matters.
For Kryonaut, sources disagree: one forum answer says no cure time, while another claims a 200-hour figure from a commenter who admitted no first-hand experience. Thermal Grizzly describes Kryonaut as a conventional non-conductive paste made of a silicone-oil carrier with nanoparticles for heat conduction, and its FAQ does not list a burn-in step.
What Early Changes Actually Come From
| Possible cause | Real effect? | What to do |
|---|---|---|
| Paste spreading and settling over thermal cycles | Small and plausible | Use the PC normally and recheck after a day or two |
| True chemical curing | Only for a few pastes such as Arctic Silver 5 | Check the manufacturer’s note; ignore for MX-4 and Kryonaut |
| Room temperature and weather changes | Often larger than any paste effect | Log ambient temperature with each run |
| Different fan curve, BIOS update or background software | Frequently the real cause | Keep settings unchanged between comparisons |
| Uneven mounting pressure or a protective film left on the cooler | Large, immediate effect | Reseat the cooler |
| Pump-out or drying over a long period | Real but slow, across months or years | Repaste on a long maintenance cycle |
How to Handle a Fresh Install
Apply Paste Properly
- Power off, unplug the PC and, if the cooler is installed, remove it. Clean the processor’s metal top and the cooler’s base completely; the surface must be free of grease.
- Let paste warm to room temperature. Thermal Grizzly notes that paste at room temperature performs best.
- Use a small amount. Forum advice is a pea-sized dot, and the same sources warn that too much paste insulates instead of conducting. Thermal Grizzly says a drop of roughly 3 mm across is enough to cover a typical processor surface.
- Lower the cooler straight down, without twisting or sliding it, so the paste spreads evenly under pressure. If you spread the paste by hand instead, Thermal Grizzly advises working slowly, with a single wiping motion taking about three seconds.
- Tighten the mounting screws in a cross pattern, a little at a time, until they stop or reach the cooler’s stated limit.
- Connect the cooler’s fan or pump to the correct header, then check temperatures in the BIOS before booting the operating system.
Measure Without Fooling Yourself
- Record a baseline before the swap if you can: idle and sustained-load temperatures, with fan speed and room temperature.
- After the install, run the same load for the same time, with the same fan curve.
- Compare at the same clock speed and power level. A processor that boosts higher will run hotter without any paste problem.
- Repeat after a few days of normal use. Treat a change of a couple of degrees as noise unless it repeats consistently.
Should You Reseat if Early Temperatures Are High?
| What you see | Verdict | Action |
|---|---|---|
| Temperatures similar to or a few degrees off expectations | Normal | Leave it and recheck after normal use |
| Temperatures far above what this cooler achieved before | Probably a mounting or application fault | Reseat the cooler |
| One core much hotter than the others | Uneven contact | Reseat and tighten in a cross pattern |
| System throttles or shuts down under load | Serious contact or cooling fault | Stop and check the cooler immediately |
| Temperatures climb slowly over months | Dust or aging paste | Clean the cooler fins and consider repasting |
Community advice also notes that an undersized cooler can look like a paste problem: in one forum case, a 65-watt rated cooler on a 95-watt processor was simply too small. Check that your cooler’s rating suits your processor before blaming the paste.
If It Does Not Work
- Remove the plastic film. New coolers often ship with a protective film over the base. Leaving it on is a common cause of very high temperatures.
- Check the mount. Make sure the backplate, standoffs and all retention screws are seated. Worn plastic retention pins can fail after years of heat cycles.
- Re-clean both surfaces. Old residue, fingerprints or oil keep paste from bonding well.
- Look at the paste spread. After lifting the cooler, a thin, even print across the processor means good contact. Large dry areas mean uneven pressure.
- Check the fan or pump header. Confirm the cooler is connected to the right header and spins at the expected speed.
- Verify airflow. Dust-clogged fins or restricted case airflow raise temperatures independently of the paste.
- Handle liquid metal separately. It conducts electricity and can corrode aluminum, so it needs different care from the pastes in this article.
Gear That Helps
ARCTIC MX-4 (4 g) – a dependable no-fuss paste
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ARCTIC lists MX-4 as a grey, metal-free, non-conductive compound with a viscosity of 31,600 poise, a density of 2.50 grams per cubic centimeter and a continuous-use range of minus 50 to 150 degrees Celsius. It describes the paste as non-drying and non-bleeding, and its page lists no burn-in step. The 4 g size covers several applications. It is a thermal paste rather than an adhesive, so it will not hold a cooler by itself.
ARCTIC MX-7 (4 g, with MX-Cleaner) – paste plus cleaner in one pack
MX-7 is sold in several sizes, and this listing adds ARCTIC’s MX Cleaner for removing the old compound. That cleaner is handy if you are replacing paste on a used cooler. Detailed viscosity, conductivity and temperature figures for MX-7 were not confirmed here, so check them on the listing before relying on them. Use the same method as any paste: a small dot, even mounting pressure and a clean surface.
ARCTIC MX-7 (8 g) – the larger tube for repeated jobs
The 8 g size is aimed at people who repaste several PCs or like to refresh paste regularly. The listing highlights long durability, but confirm the exact claim and any numbers on the listing. ARCTIC says unopened paste can be stored for up to 8 years and syringes can be resealed. For a single build, the smaller 4 g option is plenty.
Thermal Grizzly Kryonaut (1 g) with cleaning wipes – a small, premium syringe
Thermal Grizzly describes Kryonaut as a conventional paste, non-conductive, with a silicone-oil carrier and nanoparticle filler. It says a drop about 3 mm across suffices for a typical processor and that properly stored paste lasts at least three years. One gram is enough for a few applications, not many, and the bundle adds six wet and six dry wipes for cleaning. Confirm the exact pack contents on the listing.
Generic Thermal Paste 1.8 g with Toolkit – a basic option, details unconfirmed
This listing offers 1.8 g of paste with a small toolkit for CPU, GPU and other components. The title names no brand and gives no conductivity, composition or temperature rating, so confirm those on the listing before use, especially whether the paste is electrically conductive. It suits a quick job when you need a spreader and cleaning basics, but there is no way to verify performance claims from the title alone. Treat it as a runner-up to a branded paste.
Common Mistakes
- Applying too much paste. A thick layer insulates and can squeeze onto the socket area. Use a small dot.
- Leaving the cooler’s protective film on. Check the base before mounting.
- Judging temperatures at different room temperatures. Log ambient conditions with every comparison.
- Uneven tightening. Tighten screws in a cross pattern so pressure builds evenly.
- Reusing old paste. Clean both surfaces fully and apply fresh paste each time you remove the cooler.
- Blaming the paste first. Cooler size, airflow and fan settings explain many high readings.
Questions
How long should I wait before judging my cooler?
With non-curing pastes, you can judge immediately for gross problems and recheck after a day or two of normal use for fine differences. If temperatures are drastically wrong from the first boot, reseat rather than wait.
Does re-pasting reset the cure clock?
Only for pastes that actually need curing. For MX-4 and Kryonaut, the makers list no such step, so there is nothing to reset. If you use a paste that does specify burn-in, expect the clock to restart.
Is MX-4 electrically conductive?
ARCTIC states it is metal-free and not electrically conductive, with a volume resistivity of 3.8 times 10 to the 13th ohm-centimeters. Always check conductivity on any other paste before use, since silver-based and liquid-metal products can carry a short-circuit risk.
Does thermal paste expire?
Makers publish storage figures: ARCTIC says unopened paste lasts up to 8 years, and Thermal Grizzly says at least 3 years when stored properly with the cap secured. Applied paste can slowly degrade over many months or years, especially through pump-out from repeated heating and cooling.
Should I use extra paste to be safe?
No. Extra paste does not improve contact and can act as an insulator. A small dot that spreads under cooler pressure is the usual advice.
Why are my temperatures lower after a few days?
Possible reasons include slight paste settling, a cooler room, or changed background load. A controlled comparison with the same fan curve and workload shows which one applies.
Update History
- October 20, 2026 – Updated with specification checks and a revised product comparison.
- Check the product page for current specifications and availability before buying.
Sources
- ARCTIC MX-4 product page and support FAQ
- Thermal Grizzly FAQ
- Vortez ARCTIC MX-4 review
- Tom’s Hardware forum threads on thermal paste break-in, MX-4 versus Arctic Silver 5, and post-repaste temperatures
- Wikipedia entry on thermal grease
- Retailer product listings for the five pastes
