A grease rated for high temperature costs more and is worth specifying only when the service condition actually demands it. Five conditions do, and in each one a standard grease fails by a different mechanism — so recognising which condition applies also tells you which property to specify. Condition 1: Vacuum or Reduced-Pressure Service This is the condition where a mechanically adequate grease causes the most damage. Under reduced pressure, the volatile components in an ordinary hydrocarbon grease evaporate out of the joint and into the system the grease was applied to seal. The symptom is not a failed joint but a system that will not perform: pump-down takes longer than it should, base pressure never stabilises where it ought to, and the evaporated material redeposits on nearby optics or sensitive surfaces. Low volatility, not temperature rating, is the governing specification here. Incure's Pyra-Sil™ 802 high vacuum silicone grease is formulated for exactly this duty across a −45°C to 204°C range. The reason substitution is a genuine risk rather than a small compromise is that the volatility difference is invisible at assembly — it only appears once the system is already under vacuum. Condition 2: Wide Thermal Cycling on a Static Seal Constant heat is not the only trigger. A joint that heats and cools repeatedly puts a different demand on the grease: it must stay conformable at the cold end without stiffening, and stay in place at the hot end without thinning and migrating off the sealing face. A formulation rated only around ambient will stiffen in cold service and lose the conformability that let it fill surface irregularities in the first place, or soften in hot service and creep away from the joint under gravity. A thixotropic gel consistency is what resists the second failure — the grease stays where it was applied on a flange face or O-ring rather than dripping or migrating, which matters as much on a joint that sits untouched for years as during application. Condition 3: Proximity to a Radiant Heat Source A component can run far above ambient without being part of the hot process at all. Radiant heat from a furnace wall, a steam line, or a heating element will push a nearby seal or interface well past room temperature. Do not specify against the room reading. Measure the actual surface temperature of the part with a contact probe, and specify to that number. Where the surrounding heat load is itself the problem, reducing it is often cheaper than upgrading the grease: a high-emissivity ceramic coating radiates heat away from a housing or enclosure and lowers the temperature the grease has to survive. Condition 4: Joints That Must Be Reopened Where a flange, fitting, or ground-glass joint is opened and reseated repeatedly, the grease has a second job beyond sealing — preventing seizing so the joint can actually be separated later without damage. This is the condition that rules out a cured sealant: a cured material makes a better permanent seal…

Every material outgasses to some degree, and vacuum grease is no exception. The question that matters is how much and how fast. A conventional grease floods a chamber with vapor within minutes; a properly formulated high vacuum grease releases so little that a well-designed system still reaches its target base pressure. The Science of Outgassing Outgassing is the release of gases that were adsorbed on, absorbed into, or dissolved within a material. When chamber pressure drops, the equilibrium shifts and those molecules leave the surface. For a grease, the dominant source is the vapor pressure of its own base fluid plus any volatile additives. A standard grease is engineered for atmospheric pressure and contains light fractions and package additives that have appreciable vapor pressure at room temperature. Under vacuum these evaporate rapidly. A high vacuum grease is built from stable, high-molecular-weight base fluids, usually silicone or perfluorinated polyether, and is refined to remove the volatile tail, so its equilibrium vapor pressure is orders of magnitude lower. Why Outgassing Matters System contamination: outgassed molecules condense on cooler surfaces, leaving films on optics, detectors, and electrical contacts that degrade performance or cause failure. Base pressure: the vapor adds gas load the pumps must remove, which can make a deep or ultra-high vacuum unreachable. Process yield: in deposition and coating equipment, a hydrocarbon film on a substrate ruins adhesion and electrical properties. Seal life: as volatile fractions leave a conventional grease, it stiffens and loses sealing and lubricating function, shortening O-ring and stopcock service life. How Low-Outgassing Grease Is Made Formulators select a base fluid with inherently low vapor pressure, then vacuum-strip it to remove residual light ends. Fillers such as fumed silica provide the thixotropic body that keeps the grease in the joint without introducing volatiles. The finished product is often characterized by total mass loss and by collected volatile condensable material under standardized vacuum-thermal test conditions, and the published figures let engineers predict behavior in their own systems. Temperature drives the rate. Outgassing roughly follows an exponential relationship with temperature, which is why a bake-out, running the empty system hot under pump, accelerates the release of the remaining volatiles so they can be removed before real work begins. Email Us with your base pressure target and bake-out capability for help selecting a grade. Managing Outgassing in Practice Use the minimum quantity of grease. Outgassing scales with exposed surface area and volume, so a thin translucent film outgasses far less than a thick layer, and it also seals better. Bake the system after assembly where components allow it. Confirm the grease is rated for the bake temperature, since exceeding it can decompose the base fluid and create new volatile species. Keep grease off surfaces that do not need it. Wipe away everything squeezed out of a joint, and avoid smearing grease across chamber walls or internal fixtures. Where a joint sees wide temperature swings, differential expansion between dissimilar materials continuously works the film, a stress mechanism related to how a CTE mismatch…

For manufacturers and industry professionals, "grease" often calls to mind a one-size-fits-all lubricant. In demanding vacuum and pressure applications, nothing could be further from the truth. The Core Types of High Vacuum Grease High vacuum greases are typically categorized by base material, which dictates their core properties and ideal use cases. The two most common types are silicone-based and hydrocarbon-based. Silicone-based grease is the workhorse of the industry, built from a silicone polymer base with a thickening agent added for body. Its key characteristics include strong thermal stability across a wide range — from cryogenic lows to over 200°C — along with resistance to oxidation, water, and many chemicals. Many formulations are also non-conductive, adding a layer of protection for electrical components, and exhibit low outgassing that suits high- and ultra-high vacuum work. This combination makes silicone grease the better fit for general-purpose vacuum sealing, high-temperature applications, and projects needing both thermal and electrical insulation. Hydrocarbon-based grease, derived from petroleum or synthetic hydrocarbons, has a long history in vacuum technology. It provides effective sealing, particularly for ground glass joints and O-rings, at a generally lower cost than silicone counterparts — a reasonable trade-off for projects that don't need extreme thermal stability. It's also typically easier to clean using common solvents like hexane or acetone, which matters for applications where high temperatures aren't a factor and cost or specific material compatibility takes priority. Viscosity and Consistency Considerations Beyond the silicone-versus-hydrocarbon decision, viscosity and consistency also shape how a grease performs in a given joint. A stiffer, higher-viscosity grease resists being squeezed out of a joint under mechanical load or repeated thermal cycling, which matters for flanges and fittings that see frequent vibration. A softer, more fluid grease spreads more easily across a large surface area and can be preferable for delicate glassware where excessive pressure during application risks cracking a joint. Thixotropic formulations — which thin under the shear of application but firm back up once at rest — try to offer both properties at once, spreading easily during assembly while resisting migration once the joint is closed and under vacuum. Actionable Advice: How to Choose Four factors should drive your selection: Temperature Range: What's the maximum and minimum operating temperature? A wide range or high heat generally points toward a silicone-based grease. System Environment: Is this a high vacuum chamber, high-pressure line, or chemically aggressive environment? Chemically inert, low-outgassing silicone formulations are often preferred here. Materials Compatibility: What will the grease contact? While silicone-based greases are broadly versatile, certain plastics or elastomers may pair better with hydrocarbon greases — always check technical data sheets. Application and Maintenance: How often will you clean and reapply? Hydrocarbon grease's easier solvent removal can help with frequent cleaning cycles, though silicone's longevity can reduce how often maintenance is needed in the first place. Storage, Shelf Life, and Handling Grease selection doesn't end once the right base chemistry is chosen — how it's stored and handled afterward affects performance just as much. Silicone-based vacuum greases…

In manufacturing, research, and high-tech industries, seal integrity isn't a luxury — it's a fundamental requirement. The question is knowing exactly when a standard lubricant or sealant won't cut it. 1. High Vacuum and Ultra-High Vacuum (UHV) Systems This is the most obvious use case. In vacuum systems, a leak can compromise an entire process. High vacuum grease is engineered with extremely low volatility to prevent outgassing — the release of vapors into the vacuum chamber. Outgassing from a standard grease can contaminate the vacuum, ruining sensitive experiments or manufacturing processes, and can create a virtual leak that makes it impossible to reach the required vacuum level. Practical applications include: Sealing ground glass joints: In laboratory settings, high vacuum grease creates a tight seal in glassware used for distillation or vacuum filtration. Protecting O-rings and gaskets: In vacuum pumps, chambers, and flanges, it lubricates and seals to prevent leaks and extend seal lifespan. Lubricating moving parts: For internal components that require movement, it provides lubrication without contaminating the environment. 2. Extreme Temperatures Many high-performance applications involve environments with significant temperature swings, from cryogenic lows to intense highs. Standard greases either freeze and crack or melt and run, compromising both seal and lubrication. High vacuum greases with a silicone base are formulated for strong thermal stability, often maintaining consistency from well below freezing to over 200°C. That range matters for chemical processing equipment sealing valves and joints handling hot or cold fluids, and for aerospace components lubricating parts that swing between direct sunlight and shadow in a matter of minutes. 3. High Pressure and Corrosive Environments While the name suggests a vacuum-only focus, the properties that make these greases effective under low pressure also make them useful sealants in high-pressure systems. Chemical inertness is the other key factor — a robust, chemically resistant grease prevents leaks and protects seals from degradation by harsh chemicals, acids, or gases in industrial pneumatic and hydraulic systems, as well as in equipment handling corrosive fluids. 4. Electrical and Electronic Applications The non-conductive, insulating nature of many high vacuum greases makes them valuable well beyond sealing duty. A grease that also functions as an effective electrical insulator can protect components exposed to environmental stressors — protecting connectors and terminals from moisture and oxidation in power systems, or encapsulating sensitive components to prevent short circuits while assisting with thermal management in electronic circuits. 5. Application-Specific Sealing in Analytical and Materials Research Beyond production equipment, high vacuum grease shows up constantly in analytical instrumentation and materials research settings, wherever a vacuum or controlled atmosphere is part of the measurement itself. Mass spectrometers, electron microscopes, and thin-film deposition chambers all depend on a stable vacuum to produce accurate results, and any outgassing from a poorly chosen grease can deposit a contaminant film directly onto optics, detectors, or sample surfaces. In these settings, the grease isn't a peripheral consumable — it's effectively part of the instrument's specification. Common Mistakes to Avoid Even when the right grease is on hand, a…

The most common vacuum-seal failure is not the wrong grease, it is too much of the right grease. A thick layer traps air, raises the outgassing load, collects particulates, and can still leak. The target is a thin, translucent film that fills surface roughness and nothing more. The "Sheen, Not a Slather" Principle Leaks at a demountable joint occur through microscopic scratches and pores in the sealing surfaces. A very small amount of grease bridges those imperfections and creates a continuous barrier. Adding more does not improve the seal; it adds volume that must be pumped away and gives dust something to stick to. The visual target is a surface that reflects light with a faint translucent sheen. If you can see distinct beads, ridges, or an opaque white coating, there is too much grease on the joint. Step 1: Prepare the Surfaces Remove all old grease with a lint-free wipe and a solvent compatible with the components, then let the surface dry completely. Inspect ground-glass joints and O-ring grooves for chips, cracks, or embedded grit, since no amount of grease will seal a damaged surface. Wear clean, powder-free gloves. Skin oils are volatile contaminants that will outgas in the chamber, so never handle a cleaned sealing surface with bare hands. Step 2: Take a Small Amount Place a bead no larger than a grain of rice on a gloved fingertip or a clean applicator. You can always add a little more; removing excess from an assembled joint is far harder and usually means starting over. Step 3: Apply and Distribute For an O-ring, roll it between two greased fingers so a thin film transfers to the whole circumference, then seat it in its groove. For a ground-glass joint, lay a narrow stripe of grease around the upper half of the inner cone, keeping it away from the tip so grease is not pushed into the system interior. Bring the parts together and rotate them through a partial turn. This shears the grease into an even, continuous layer and drives excess outward rather than inward. The joint should look uniformly translucent when seated. Step 4: Inspect and Clean Up Confirm a thin, even, translucent film with no gaps and no thick globs. Wipe away every trace of grease that has squeezed out of the joint with a clean lint-free cloth, because exposed grease on the outside of a fitting collects debris and, on an internal surface, adds to the outgassing load. Email Us if you are seeing repeat leaks at a specific joint type and our team can help diagnose the cause. Common Mistakes to Avoid Over-application, which is the single largest source of contamination and particulate pickup. Greasing a damaged or dirty surface instead of repairing or cleaning it first. Using a silicone grease where process solvents will attack it, causing the film to migrate and the seal to fail. Applying grease to the dynamic sealing face of a rotary feedthrough beyond the manufacturer's guidance, which can pump grease…

High vacuum grease is a specialized sealing and lubricating compound engineered for exceptionally low volatility. In a vacuum, ordinary greases evaporate, contaminating the chamber and raising base pressure. A high vacuum grease is formulated to stay put, holding a seal at ground-glass joints, O-rings, and rotary fittings without outgassing into the system. The Defining Property: Low Volatility Every material releases trapped and dissolved gases when the surrounding pressure drops. A conventional grease contains light hydrocarbon fractions and additives that boil off quickly under vacuum, coating optics and sensors and preventing the system from reaching a deep vacuum. High vacuum grease starts from stable, high-molecular-weight base fluids, most often silicone or, for solvent resistance, perfluorinated polyether. The product is refined to strip volatile fractions, so its vapor pressure at room temperature is extremely low and its rate of mass loss under vacuum is negligible over long service intervals. Key Properties Beyond Volatility Wide thermal range: silicone-based vacuum greases typically hold their consistency from around minus 40 degrees Celsius to over 200 degrees, so a joint stays sealed through bake-out and cool-down. Chemical inertness: the base fluids resist reaction with common process gases, acids, and bases, and perfluorinated grades add resistance to oxygen service and aggressive solvents. Electrical insulation: most vacuum greases are strong dielectrics, useful for sealing electrical feedthroughs. Water repellency: a thin film fills microscopic surface roughness where leaks originate and blocks moisture ingress. Where High Vacuum Grease Is Used Vacuum systems are the primary application: sealing demountable joints, lubricating stopcocks and valves, and dressing O-rings on chamber doors and flanges to fill surface imperfections. It is also used on scientific instruments, where moving parts must be lubricated without contaminating a sensitive beam path or detector, and in semiconductor and coating equipment, where any deposited residue can spoil a process run. Outside vacuum work, the same low-volatility, wide-temperature, chemically inert film makes these greases useful for valves and fittings in chemical processing and for sealing and protecting connectors in equipment that sees drastic temperature changes. Email Us with your base pressure, temperature range, and chemical exposure for guidance on selecting a grade. Choosing the Right Grade Start with the vacuum level. For rough and medium vacuum a general silicone grease is adequate; for high and ultra-high vacuum, choose a grade with a published vapor pressure low enough to protect your base pressure, and plan for a bake-out procedure. Match the temperature range to the full cycle the joint sees, including any bake-out. Confirm chemical compatibility with process gases and cleaning solvents, since a silicone grease attacked by a solvent will migrate and fail. Where the sealed joint also experiences thermal cycling, differential expansion between a glass or ceramic part and a metal fitting works the grease film, a stress mechanism related to how a CTE mismatch causes bonded and sealed joints to fail. For assemblies that combine vacuum service with high external temperatures, a high-emissivity ceramic coating on the housing exterior can manage surface heat independently of the seal. High…