Mercury porosimetry: Principles, applications, and how the AutoPore delivers

Understanding a material’s pore structure is essential to predicting its behavior, from fine-tuning drug release rates in pharmaceuticals to optimizing ion transport in batteries.

One of the most effective methods for this is mercury intrusion porosimetry, which uses pressure to force mercury into the pores of a material, generating valuable pore size distribution, pore volume, and porosity data.

However, mercury porosimetry presents several operational challenges. Strict safety protocols, the potential for sample compression or damage, and incorrect assumptions about pore geometry can all affect your analysis.

You need the right instrumentation – and the right analytical approach – to get reliable R&D and QC outcomes.

In this blog, we’ll outline key mercury porosimetry principles to help you elevate your pore characterization workflows. We’ll also show how the Micromeritics mercury porosimeter offers gold-standard speed, safety, and accuracy across a vast measurement range.

What is mercury porosimetry?

Mercury intrusion porosimetry, often abbreviated to MIP, is a powerful and versatile porosimetry technique that analyzes the pore architecture of solid materials by applying pressure to force mercury into their pores.

This method enables you to characterize your materials:

• Pore size distribution
• Median pore diameter
• Total pore volume
• Sample densities (both bulk and skeletal)
• Total pore surface area

These pore properties indicate the overall pore architecture of a material, which gives you insight into its potential properties, from fluid flow and thermal conductivity to mechanical strength and ion transport.

What is the measurement range of mercury intrusion porosimetry?

A typical mercury porosimeter measures pore size from approximately 3nm up to 1100µm.

The upper limit of measurement is usually determined by the instrument’s pressure capacity, and if the pressure isn’t strong enough, the mercury porosimeter may not be able to fill smaller mesopores and return accurate data.

The AutoPore from Micromeritics offers a measurement range from 3 nm up to 1100 µm, giving operators deep insights into microporous and mesoporous materials. This is especially important when characterizing materials like Li-ion battery separators, where transport and flow through large macropores determine the material’s properties.

How does the mercury porosimetry process work?

Mercury intrusion porosimetry works by forcing liquid non-wetting mercury into the pores of a material under controlled pressure. At the lowest pressures, larger pores will fill first, followed by smaller ones as the pressure climbs.

By gradually increasing pressure and measuring the volume of mercury intruded at each step, this technique allows for the calculation of total pore volume, pore size distribution, and porosity.

As mercury does not naturally enter pores without applied pressure, the amount of pressure required by the mercury porosimeter to force it into the pores is inversely proportional to the size of the pores, and can therefore be calculated using the Washburn equation:

Pd = –4𝑦cos⁡θ

In this equation:

• d is the diameter of a pore
• P is the pressure applied
• γ is the surface tension of the mercury (usually 485 dynes/cm under controlled conditions)
• θ is the contact angle between the mercury and the sample (typically assumed to be 130° for most solids)

Modern instruments such as the AutoPore V improve the accuracy of this calculation by precisely controlling pressure ramps, measuring intrusion volume at high resolution, and compensating for factors such as temperature-dependent mercury density.

What are the steps of a mercury porosimetry test?

When conducting tests on a mercury intrusion porosimeter, your operators will go through six key steps.

1. Sample preparation

The sample is dried, removing moisture and volatiles to avoid measurement interference.

The penetrometer (a glass or metal vessel) is selected and sized for the sample. Many instruments, like the AutoPore V, offer a variety of penetrometer sizes to optimize for sample size and shape.

Careful sealing and calibration of the penetrometer is crucial, as leakage, trapped air, or incorrect stem volumes will degrade accuracy.

2. Mercury filling

The penetrometer is evacuated to remove trapped air, meaning that pressure corresponds only to pore filling and not to compressing trapped gas.

Mercury is introduced under a vacuum into the penetrometer.

3. Low-pressure intrusion

The sample is first subjected to low pneumatic pressures of 0.2–50 psia to intrude larger macropores (~900–3.6 µm).

Pressure is increased, and the volume of intruded mercury is recorded. The porosimeter translates volume changes into pore volume.

4. High-pressure intrusion

To fill smaller pores (mesopores and small macropores), much higher pressure is applied; the AutoPore V supports models rated to 33,000 psia and 60,000 psia.

Throughout, very fine control over pressure and volume is needed to resolve small pores accurately.

Compensation for effects like material compression and mercury density changes with temperature is critical.

5. Extrusion

After maximum pressure is reached, the pressure is reduced, and mercury may extrude from the pores.

However, due to contact-angle hysteresis and “ink-bottle” pores, some mercury may remain trapped.

The difference in mercury volume between intrusion and extrusion can provide insight into pore shape, neck-to-body ratio, connectivity, and hysteresis effects.

6. Data analysis and pore size calculation

The instrument uses the pressure-volume data and the Washburn equation to compute pore diameters, distributions of pore volume vs. pore size, cumulative pore volume, median pore diameter, pore surface area, porosity, and bulk and skeletal densities.

Additional metrics like tortuosity, permeability, entrapped volume, fractal dimension, or throat-to-cavity size ratios can also be computed.

Why do efficiency and precision matter in the mercury intrusion porosimetry workflow?

Every stage of a mercury porosimetry test relies on precise pressure control, accurate volume measurement, and stable, contamination-free handling of the sample and mercury.

Small inefficiencies, such as incomplete evacuation, poor penetrometer sealing, or inaccurate pressure stepping and insufficient equilibration time, can result in large errors in the calculation of pore architecture.

Modern mercury intrusion porosimeter instruments employ automation, diagnostics, and intelligent corrections to maintain accuracy and speed.

For example, the Micromeritics mercury porosimeter, AutoPore V, uses:

• Guided method setup to minimize operator error, ensuring consistent test parameters, proper penetrometer selection, and correct configuration for the target pore-size range.
• Fine pressure resolution to prevent misclassification of pore sizes, enabling accurate intrusion and extrusion data, even in materials with narrow or complex pore distributions.
• Automated evacuation and filling to eliminate inconsistencies caused by manual handling, improving repeatability and reducing errors from incomplete degassing or variable fill rates.
• Real-time compensation for mercury and sample compression to avoid distortion of pore-volume calculations, ensuring true pore structures are measured even under high-pressure conditions.

Where macro-/meso-pore characterization directly affects catalyst performance, ceramic reliability, battery electrode design, and filtration properties, these technological efficiencies translate into more reliable insights, higher throughput, and greater confidence in material decisions.

7 advantages of using mercury intrusion porosimetry

With many options for pore characterization out there, why should you turn to mercury porosimetry over other methods?

1. Broad pore size measurement range

A key advantage of mercury intrusion porosimetry is its exceptionally broad measurement range: Mercury porosimetry can characterize pores from roughly 1100µm down to around 0.003 µm (3 nm).

Many materials exhibit hierarchical porosity, where large transport pores coexist with smaller pores. Few techniques can span multiple orders of magnitude, so researchers often need multiple instruments to cover the full range.

With mercury porosimetry, all pore types can be characterized in a single test.

2. Quantitative, high-resolution results

Mercury intrusion porosimetry directly links applied pressure to pore diameter via the Washburn equation. From a single measurement, it can provide:

• Pore-size distribution
• Cumulative pore volume
• Porosity
• Bulk and skeletal density
• Median pore diameters and pore-throat analysis
• Intrusion/extrusion hysteresis

This breadth of quantitative information makes mercury porosimetry valuable both for routine QC and advanced research.

3. Superior speed and efficiency

Techniques such as gas adsorption often need long equilibrium times or separate instruments to cover different pore ranges. Mercury porosimetry delivers full-range pore-size analysis at pace.

Modern automated systems like the AutoPore V can complete a full cycle in mere hours, providing rapid turnaround for industrial workflows and time-sensitive R&D programs.

This method’s pressure-driven mechanism also allows the instrument to move rapidly through the pore-size spectrum, reducing bottlenecks and supporting high-throughput workflows.

4. Applicability to a wide range of materials

Because mercury intrusion porosimetry relies on pressure-driven intrusion rather than adsorption, evaporation, or capillary flow of wetting fluids, it can be applied to almost any solid with accessible pores, including:

• Battery electrodes and separator materials
• Ceramics
• Catalysts and supports
• Concrete, cement, and construction materials
• Polymers and membranes
• Filtration and separation media
• Geological and soil samples

This versatility makes mercury porosimetry a universal tool for materials with structural or transport-critical porosity.

5. Complementary to other porosity techniques

Mercury intrusion porosimetry does not replace gas adsorption or capillary flow porometry – instead, it complements them.

While mercury porosimetry excels in macropore and large-mesopore analysis, gas adsorption provides higher sensitivity for micropores and small mesopores, and capillary flow porometry offers direct pore-throat and through-pore information.

Combining these methods yields a more complete understanding of hierarchical pore networks, helping researchers design better catalysts, optimize electrode porosity, engineer stronger ceramics, and develop more efficient filters, among other applications.

6. Simpler sample preparation

Unlike gas adsorption, which requires long, high-temperature degassing, and CFP, which often demands careful wetting and drying, mercury intrusion porosimetry typically requires minimal sample preparation beyond drying and placement in a penetrometer.

This reduces operator workload, analysis time, and the risk of sample damage.

7. Large sample size compatibility

Finally, mercury porosimetry can accommodate relatively large sample volumes (depending on penetrometer size).

This delivers more statistically representative results that represent real-world variability than techniques that rely on small powder quantities. This is particularly useful for heterogeneous materials like concrete, catalyst beads, or battery electrodes.

Mercury porosimetry vs. BET gas adsorption: Which should I use?

One common alternative to mercury porosimetry is gas adsorption, which measures surface area using the Brunauer–Emmett–Teller (BET) method, as well as pore volume and pore size distribution of mesopores and micropores using methods such as Barrett-Joyner-Halenda (BJH) and density functional theory (DFT).

Gas adsorption is the industry standard for quantifying exposed surface area and pore size distribution on the molecular scale, particularly when dealing with microporous and mesoporous materials.

However, mercury intrusion porosimetry provides several crucial advantages over gas adsorption for the analysis of real-world porous materials such as catalysts and battery components:

• Firstly, mercury porosimetry measures a much broader pore-size range than gas adsorption, from mesopores to macropores, putting it beyond the pore-size range accessible through gas adsorption.
• Additionally, because mercury porosimetry detects pore-throat entry pressure, it reveals structural features that gas adsorption cannot, including permeability and tortuosity.
• Finally, mercury porosimetry delivers direct measurements of porosity, pore volume, and density, and can analyse larger or irregular samples without grinding or extensive degassing.

Gas adsorption still excels at molecular-scale surface area and microporosity analysis and should therefore be the go-to for many materials, such as highly porous powders.

However, if your material exhibits a wide pore-size distribution, or if you need further insights into pore architecture, throat size, or bulk porosity, mercury porosimetry is the most informative technique for your workflow.

For the most comprehensive insight, combining insights from your mercury intrusion porosimetry tests with gas adsorption can give you a fuller picture.

The Micromeritics AutoPore: A modern mercury intrusion porosimeter

The AutoPore from Micromeritics is a state-of-the-art mercury intrusion porosimeter designed to deliver fast, accurate, and reliable pore-structure analysis across a broad measurement range.

One of the industry’s most widely adopted systems, it combines high-pressure capability, fine pressure control, robust safety engineering, and advanced software for seamless data visualisation and reporting, supporting both high-throughput QC workflows and advanced materials R&D.

What are the key applications for mercury porosimetry?

The AutoPore V is widely used across industries where pore structure directly affects performance, durability, or efficiency. Key application areas include:

• Pharmaceuticals
  Porosity impacts drug release, stability, and manufacturability.
• Catalysts
  Catalytic activity depends strongly on the active surface area and pore structure of the catalyst.
• Ceramics
  For materials used in filtration, insulation, membranes, and structural ceramics, mercury intrusion porosimetry quantifies pore area and porosity, which impact strength, texture, appearance, and density.
• Adsorbents
  Knowledge of pore area, total pore volume, and pore size distribution is important for quality control of industrial adsorbents and separation processes, as the selectivity of an adsorbent depends on porosity and surface area characteristics.
• Aerospace
  Weight and function of heat shields and insulating materials depend on surface area and porosity.
• Battery and fuel cell electrodes
  Increasing power density in fuel cell and Li-ion electrodes and separators requires controlled porosity with high surface area.
• Geoscience
  In groundwater hydrology and petroleum exploration, porosity indicates how much fluid a structure can contain and how easy it will be to extract.
• Filtration and separation media
  Measuring pore size, pore volume, pore shape, and pore tortuosity is crucial in filter manufacturing, with pore size in particular correlating strongly with filtration performance.
• Construction materials
  Pore-size distribution plays an important role in the permeability, freeze–thaw durability, corrosion resistance, and long-term mechanical behaviour of concrete, cement, and other construction materials.
• Paper
  The porosity of print media coating impacts blistering, ink receptivity, and ink holdout, critical for offset printing.

The benefits of mercury porosimetry: Summary table

So, what are the overall benefits of mercury intrusion porosimetry, and how does the AutoPore V take them to the next level? Here’s a summary.

Benefit of mercury intrusion porosimetry	How AutoPore takes it a step further
Broad pore size range	• Measures pores from 1100µm down to 0.003 µm (3 nm), enabling continuous macropore-to-mesopore characterisation in a single run • High-pressure models (up to 33,000 psia and 60,000 psia) resolve even the smallest pore throats with precision
Quantitative results	• High-resolution pressure and volume measurement • Automatic corrections for mercury density, compressibility, and sample deformation • Outputs include pore-size distribution, porosity, cumulative pore volume, pore-throat detail, bulk & skeletal density, all in one instrument
Speed and efficiency	• Automated evacuation, filling, pressure control, and data analysis enable a complete intrusion–extrusion cycle in hours • Scanning or equilibrium modes let users choose between rapid screening and high-precision analysis • Multiple pressure ports increase sample throughput
Wide applicability	• Compatible with powders, pellets, monoliths, foams, fragile ceramics, concrete fragments, battery electrodes, and more • Multiple penetrometer sizes and geometries ensure optimal fit for diverse materials • ASTM D4284, ASTM D4404, and ISO 15901-1 compliance ensure cross-industry acceptance
Complementary data	• MicroActive software allows overlay with gas adsorption data, integration with other porosimetry techniques, interactive data modification, and advanced analysis (e.g., throat to cavity ratios, fractal dimension) • Supports cohesive multi-technique pore-structure interpretation

Advance your pore understanding with best-in-class mercury porosimetry analysis

Delivering quantitative, high-resolution insights into pore size, volume, density, and connectivity, mercury porosimetry is an indispensable technique across materials science, pharmaceuticals, energy storage, and construction.

Technologies such as the AutoPore advance this capability with precision pressure control, automation, and industry-standard compliance.

To explore how mercury intrusion porosimetry can strengthen your workflows, discover more about the AutoPore.

To see the AutoPore in action, explore related case studies and application notes in our knowledge center.