This is a practical guide to Surface Science for researchers working in the Mining and Metals Industry.
In this all-new guide you’ll learn all about:
Let’s dive right in.
In mineral processing, separation often comes down to a surface. A mineral that water wets poorly can attach to an air bubble or an oil droplet, while gangue stays in the slurry. In metal powder work, small changes at the powder surface affect how binders wet and how layers spread.
These are the places where wetting decides yield in mining and metals work:
The Dropometer drop shape analysis kit measures contact angle, surface and interfacial tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.
We use the following surface properties to understand the behavior of Mining and Metals products and improve their quality.
Sample Image taken from Droplet Lab Tensiometer.
Young – Laplace Method
Polynomial Method
Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.
Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.
In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.
This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.
Learn how Contact Angle measurement is done on our Tensiometer
For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide
These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.
Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.
The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:
● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details
Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.
This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.
Sample Image taken from Droplet Lab Tensiometer
Dynamic Surface Tension
Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).
Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.
When to use Dynamic Surface Tension Measurement
Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.
Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.
Learn how Surface Tension measurement is done on our Tensiometer
For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide
Sample Image taken from Droplet Lab Tensiometer
Learn how Surface Energy measurement is done on our Tensiometer
For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide
For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.
The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.
Sample Image taken from Droplet Lab Tensiometer
Learn how Sliding Angle measurement is done on our Tensiometer
For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide
Within the Mining and Metals industry, several case studies exemplify the advantages of conducting surface property measurements.
Flotation works because collectors make target mineral surfaces repel water, so particles attach to air bubbles. Water contact angle on a polished mineral surface, before and after collector treatment, shows whether the treatment worked. Comparing the target mineral with silica gangue shows how selective the reagent is.
Frothers act on the liquid side. Surface tension across a dilution series shows how surface active each candidate frother is. Time resolved pendant drop readings show how fast it adsorbs over the first seconds, as explained under dynamic surface tension.
Rare earth minerals are often separated from similar gangue minerals by flotation, so reagent choice matters. Surface free energy shows how a reagent treatment changes a mineral surface, and whether that change differs between minerals.
Surface free energy is worked out from contact angles of two or more probe liquids on the same surface. Our contact angle to surface energy calculator does the arithmetic, and the surface energy measurement guide explains the method.
Coatings on conveyors, chutes and processing equipment are meant to shed water and slurry. Water contact angle and sliding angle show whether a coating still repels water after wear, cleaning or time in service. The sliding angle guide explains the roll off method.
Coating life also depends on adhesion to the metal underneath. ASTM D3359 measures that adhesion with a tape test after cuts through the film. A contact angle check on the prepared surface flags contamination before coating, but it does not replace the tape test.
Oil agglomeration recovers fine particles that are hard to float, by binding water repellent particles together with oil droplets. It works when the oil wets the target particles better than water does.
Pendant drop interfacial tension between the oil and the process water shows how reagents and water chemistry change that interface. Water contact angle on the treated mineral surface shows which particles the oil is likely to collect. Our surface tension guide covers the pendant drop method.
If you are interested in implementing these or any other applications, please contact us.
In an industry where precision reigns supreme, how can Mining and Metals manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.
A destructive tape test that rates adhesion of a cured coating to a substrate by cutting the film (X-cut or crosshatch), applying pressure-sensitive tape, and evaluating coating removal on a 0-5 scale (higher = better). In this guide, ASTM D3359 is treated as the adhesion outcome test and is paired with upstream wettability metrics (timestamped water contact angle and optional surface free energy) to turn “pass/fail” results into a corrective-action workflow.
Confirm that adhesion meets release criteria after coating + cure, and trend ratings by line/shift to catch drift.
Add pre-paint contact angle/variability (and optional SFE/Δθ) to determine whether the likely cause is surface readiness vs coating/cure changes before making process adjustments.
ASTM D3359 reports an adhesion outcome after coating and cure; it is not a root-cause tool by itself and does not resolve very high adhesion levels well. Use timestamped contact-angle/SFE trends as upstream risk signals and diagnostics, and only set numeric gates after correlating them to D3359 on representative panels from your own process.
We hope this guide showed you how to apply surface science in the Mining and Metals industry.
Now we’d like to turn it over to you:
Feel free to leave a comment below—we’d love to hear from you.
Start with the problem you need to solve. Use contact angle when the question is about a mineral, powder or coated surface, such as collector performance. Use surface tension for frothers and other reagent solutions, and interfacial tension for oil and water systems. Use sliding angle for water repellent coatings. Our contact angle and surface tension guides explain each method.
Yes, on a flat and clean surface. Polished sections give the most comparable readings. Rough or porous samples absorb or pin the drop, so the reading is an apparent angle. Record the time after the drop lands, and compare treated and untreated samples prepared the same way. See surface roughness and heterogeneity for why preparation matters.
Yes. A drop of one liquid is formed inside the other, and the drop shape gives the interfacial tension. You need the density of both liquids at the test temperature, and the drop edge must be clearly visible to the camera. See interfacial tension and the pendant drop method for the basics.
Measure water contact angle on fresh powder to set a baseline. Then measure each reuse cycle with the same drop volume, capture time and powder presentation. A rising angle or a wider spread flags moisture pickup, oxidation or contamination. Set pass and fail limits from your own bed density and defect data. Our powder bed fusion use case sets out the workflow.
ASTM D3359 measures coating adhesion with a tape test after cuts through the film. It is not a wetting method, and it sets no contact angle limit. Use contact angle as a check on surface readiness before coating, and keep the tape test for acceptance. For flotation and powder work, write your own method and record liquid, drop volume and drop age.
No. Contact angle and surface tension screen reagents and surfaces on the bench, but they do not measure grade, recovery or froth in a cell. Use them to narrow the list of collectors and frothers before lab flotation tests. Then confirm the best candidates in the cell, and keep the same sample preparation for every surface reading.
The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. Automatic edge and baseline detection gives the same reading from the same image. See our validation papers.
