Contents
Fully compliant

ASTM D7490-13: measurement of the surface tension of solid coatings, substrates and pigments using contact angle measurements

Find the surface free energy of a coating, substrate or pigment, split into dispersive and polar parts, from the contact angles of two liquids. That is what ASTM D7490 describes. The Dropometer measures both angles with ±0.35° accuracy (Dropometer product specification), on a drop shape method validated in two peer reviewed papers, and runs the split in its software or in our free calculator.

What brings you here?

Who this is for
Coatings, adhesives, ink, pigment and semiconductor teams who need surface energy analysis to explain wetting and adhesion on solid surfaces.
Compliance tier
Fully compliant: the Dropometer measures both contact angles and gives the dispersive and polar split this method describes.
Measurement
Two liquid sessile drop contact angles, ±0.35° accuracy; surface free energy up to 100 mN/m, ±0.03 mN/m accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs in the lab or beside the process.
Last updated
October 20, 2026
Book a 15 minute demo Request a quote

Free one page checklist for ASTM D7490: what to prepare, the two liquids, the settings to lock, how to run the dispersive and polar split and what to record. Made for coatings and substrate labs.

Talk to an expert

Book a 15 minute demo on your coating

Tell us your coating or substrate, your two liquids and the adhesion question you need answered. We will run the measurement live and tell you plainly where the Dropometer fits and where it does not.

Book a 15 minute demo
View the official standard
Gurdeep-Saini-Photo
Written by
Gurdeep Singh Saini
Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.
COO at Droplet Lab
Read More
Droplet-Lab logo
Technical Review by
Droplet Lab Team
Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.
Read More
Verified against SEMI/ASTM D7490-13
Gurdeep-Saini-Photo
Written By

Gurdeep Singh Saini

COO at Droplet Lab

Holds a BASc in Mechanical Engineering from Ryerson University (now Toronto Metropolitan University) and an MASc from York University. He develops the automatic edge and baseline detection behind the Dropometer's analysis.

Droplet-Lab logo
Reviewed By

Droplet Lab Team

Droplet Lab builds precision instruments and software for surface science measurement, specialising in contact angle analysis and surface tension characterisation. Used by researchers across materials science, pharmaceuticals, coatings, and advanced manufacturing, Droplet Lab's Dropometer has contributed to studies published in peer-reviewed journals including Advanced Functional Materials (Impact Factor 19). The team combines instrument engineering with deep domain knowledge in wettability science with a focus on practical accuracy.

Featured Studies & Publications

Research Paper Contact angle measurement with a smartphone
Research Paper Surface tension measurement with a smartphone using a pendant drop

Evidence box: ASTM International D7490 and the Dropometer

Standard

ASTM D7490-13(2022), Standard Test Method for Measurement of the Surface Tension of Solid Coatings, Substrates and Pigments using Contact Angle Measurements, from ASTM Subcommittee D01.23. We found no SEMI edition of this method.

Compliance tier

Fully compliant. The Dropometer measures the static contact angles of both liquids. D7490 needs a dispersive and polar split. The Dropometer software does Fowkes and van Oss Chaudhury Good. OWRK is not built in: users measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°. Surface free energy up to 100 mN/m, accuracy ±0.03 mN/m. From the Dropometer product specification.

Peer reviewed method

The drop shape method is validated against a KRUSS DSA100E in two peer reviewed papers. See our validation publications.

Customer evidence

The US R&D site of a global maker of fused silica and quartz for semiconductor, optical fibre and optics markets bought a Dropometer with the surface energy module. They have not shared results yet. Read the case study.

Published client research

Researchers used a Droplet Lab instrument to measure saline contact angle on titanium discs before and after plasma treatment. The angle on machined discs fell from 83.1° to 24.1° (Ho et al., Biomimetics, 2025). That study measured contact angle, not surface free energy. Read our analysis.

What it does not tell you

ASTM says the method is not designed as a QC or specification test. The split helps explain adhesion. It does not measure bond strength, so keep your peel or tape test.

Executive summary

What this standard measures, who uses it and how the Dropometer fits

ASTM D7490 finds the surface tension, or surface free energy, of solid coatings, substrates and pigments from the contact angles of two liquids, one polar and one nonpolar. It splits the result into dispersive and polar parts. The split rests on a simple idea: the total free energy of a surface adds up contributions from different intermolecular forces, such as dispersion forces and polar forces like hydrogen bonding. Coatings, adhesives, inks and semiconductor teams use it to explain wetting and adhesion, and to check a surface treatment. The Dropometer is fully compliant with this measurement and reads each angle with ±0.35° accuracy.

D7490 needs a dispersive and polar split. The Dropometer software does Fowkes and van Oss Chaudhury Good. OWRK is not built in: users measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator. The current edition is ASTM D7490-13, reconfirmed by ASTM in 2022. ASTM gives a working range of about 20 to 60 dyn/cm (mN/m) and says the method is for characterising surfaces, not a QC or specification test.

The Dropometer contact angle and surface energy kit runs on battery power, so you can measure coupons in the lab or beside the process. For a semiconductor workflow, see wafer cleaning and photoresist adhesion and our semiconductors guide. The US R&D site of a fused silica and quartz maker bought a Dropometer with the surface energy module. In published client research, a Droplet Lab instrument measured contact angle on plasma treated titanium.

Further reading: the surface energy measurement guide, why contact angle matters for coatings and adhesives QC, work of adhesion, sample prep and contamination control, the treated vs untreated surfaces experiment, surface free energy of common polymers and substrates and how the Dropometer compares with the Brighton Science Surface Analyst.

How the Dropometer fits the contact angle measurement

The ASTM D7490 measurement, step by step, in our own words

From coupon to a dispersive and polar split

These steps outline the procedure. They do not replace the standard. Buy the current edition and follow its liquids, drop volume, reading time and calculation rules.

±0.35°

Contact angle accuracy

From the Dropometer product specification. Display resolution is 0.01°.

±0.03 mN/m

Surface energy accuracy

From the Dropometer product specification, for results up to 100 mN/m.

About 2 min

Setup

Base plate, phone holder, LED and syringe. No PC needed.

1

Prepare the specimens

Use a cured or air dried coating, a clean substrate, or pigment pressed into a disk, as the standard describes. Handle by the edges and keep the test area free of dust and skin oils. See sample prep and contamination control.

2

Set up the Dropometer and two liquids

Level the base plate, mount the phone and LED, and fill two clean syringes: one polar liquid and one nonpolar liquid of known surface tension, as the standard specifies. Water and diiodomethane are a common pair. Lay the coupon flat on the sessile stage.

3

Measure the polar liquid

Dispense the drop volume the standard specifies and capture the drop at the set reading time. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. Place several drops on fresh spots.

4

Measure the nonpolar liquid

Change syringe and needle, then repeat on fresh spots of the same coupon with the same volume and timing. Never place a drop where the first liquid has been.

5

Calculate the dispersive and polar parts

Enter the liquid property values you have chosen and run the split. The Dropometer software does Fowkes and van Oss Chaudhury Good. OWRK is not built in: users measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator. Use the model the standard and your SOP name.

6

Record and compare

Record both mean angles, their spread, the liquids and property values, the model, the total and both parts, and room conditions. Compare coatings only when liquids and model match. For background, see work of adhesion.

7

Watch the full measurement

This video shows a complete Dropometer contact angle measurement, from setup to result. It covers the steps above in one run.

Dropometer contact angle measurement, start to finish. Repeat it with each test liquid.

Validated measurement approach

Independent benchmarking and publication-based validation references.

Peer reviewed method

The Dropometer drop shape method is 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°.

Read the validation papers

Customer evidence

We have no published client surface energy results yet. The US R&D site of a fused silica and quartz maker bought a Dropometer with the surface energy module and the two liquid method.

Read the case study

Set limits for solid coatings, substrates and pigments

ASTM D7490 · dispersive and polar parts · coatings R&D

ASTM states the method covers a total solid surface tension of about 20 to 60 dyn/cm, which is the same as 20 to 60 mN/m (source: ASTM D7490-13(2022) summary). Treat results outside that band with care.

ASTM publishes no pass or fail thresholds, and says the method is not designed as a QC or specification test. If you want limits, set them from your own correlation study: measure coatings that bonded well and ones that failed, then compare their total and polar values with your peel, tape or print results.

Your numbers depend on the liquid surface tension values you enter. Our free calculator lists water at 72.8 mN/m (21.8 dispersive, 51.0 polar) and diiodomethane at 50.8 mN/m (all dispersive), as approximate values at 20 to 25 °C. Confirm them against your own liquid table and keep them fixed. Repeat the study when you change resin, additive, cure or cleaning.

Example output: surface energy of a primer and topcoat

Example data for illustration only. These are not measured results. Your own coatings, liquids and model decide the numbers.

Example: primer and topcoat coupons, water and diiodomethane

Coupon Water angle (°) Diiodomethane angle (°) Dispersive (mN/m) Polar (mN/m) Total (mN/m)
Primer, cured62.036.041.610.752.3
Topcoat, cured76.040.039.64.944.5
Topcoat with flow additive91.052.033.21.534.7
Topcoat, handled bare hand84.048.035.43.038.4

How to read this table

Each angle is the mean of five drops. The split was calculated with OWRK in the free Contact Angle to Surface Energy Calculator, using water 72.8 / 21.8 / 51.0 mN/m and diiodomethane 50.8 / 50.8 / 0 mN/m. The Fowkes and van Oss Chaudhury Good models in the Dropometer software give their own split; do not compare numbers across models.

Example output chart

The same example data as the table, plotted as dispersive and polar parts for each coupon.

Grouped bar chart of example dispersive and polar surface energy for a primer and three topcoat coupons, showing the polar part falling with a flow additive and after handling

Example data, not measured results.

Business impact

What changes when you split surface energy instead of reading one angle

Metric Before Dropometer With Dropometer Results
What you learn One water angle, a single number Total surface energy with dispersive and polar parts ASTM D7490-13(2022) scope
Models One model typed into a spreadsheet Fowkes and van Oss Chaudhury Good in the software; OWRK in the free calculator Dropometer product specification
Result format Angle read by eye or from a shared instrument Angles to ±0.35°, surface energy to ±0.03 mN/m Dropometer product specification
Record Operator note Drop image and angle saved per measurement No published benchmark
Where it runs Shared lab goniometer Lab bench or beside the process, on battery for about 8 h Dropometer product specification

See the measurement on your own coating

Bring two coupons: one that bonded well and one that did not. We will measure both liquids live and run the split.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of the adhesion failures this test can help explain

Enter your own numbers. The defaults are examples, not Droplet Lab results.

Quality cost snapshot

Estimate what wetting related failures cost you.

Example only. Use what you see in a trial on your own samples.
Your own figure.
Your own estimate.

Result

~0
Estimated annual cost today
~0
Estimated annual cost avoided
~0
Payback period

Annual exposure combines audit/CAPA cost, customer rejections, and recall probability; avoided exposure applies the risk reduction percentage.

Measurement settings for the surface tension of solid coatings

Lock these before you compare results between batches or sites

Parameter Recommended Setting Technical Rationale
Test liquids One polar and one nonpolar liquid, as the standard specifies Two liquids give two unknowns: the dispersive and polar parts. Water and diiodomethane are a common pair.
Liquid property values Total, dispersive and polar values from one named source The split depends on these values. Changing the table changes the result.
Drop type Sessile drop, static angle The method reads resting drops of each liquid on the solid.
Drop volume As the standard specifies, fixed for every drop A changing volume adds spread that is not about the surface.
Reading time As the standard specifies, fixed for every drop Liquids can spread, soak in or evaporate, so the time must not vary.
Fit model Young-Laplace or polynomial, the same for every run Both models are in the Dropometer software. Do not mix them within one study.
Surface energy model Fowkes or van Oss Chaudhury Good in the software; OWRK in the free calculator OWRK is not built in. Name the model in your report and keep it fixed.
Replicates Several drops of each liquid on fresh spots Coatings vary across a panel, so one drop per liquid is not enough.
Environment Record room temperature and humidity The Dropometer runs at 10 to 45 °C and has no temperature control.

Is ASTM D7490 the right test?

Pick the method by the question you need answered

Start: What do you need to know about the surface?

Dispersive and polar parts of the surface

Signals:

You need to know why a coating, ink or adhesive wets or fails, not just whether it wets.

Rule-out:

Use ASTM D7490, this page. The Dropometer is fully compliant.

One wettability number with water

Signals:

You want a single advancing water angle to compare coatings, substrates or pigments.

Rule-out:

Use ASTM D7334. The Dropometer measures advancing angles by adding liquid through the needle.

Fast cleanliness check by eye

Signals:

You want a quick check for hydrophobic films after cleaning, without an instrument.

Rule-out:

Use the water break test in ASTM F22. Contact angle complements that check with a number.

Whether the coating actually sticks

Signals:

You need a rating of coating adhesion, not of surface wetting.

Rule-out:

Use the tape test in ASTM D3359. Surface energy complements it by explaining failures.

Decision tree at a glance

Start from the question you need answered. Blue boxes are measurements the Dropometer runs.

Decision tree for choosing between ASTM D7490 two liquid surface energy, ASTM D7334 advancing water angle, the ASTM F22 water break test and the ASTM D3359 tape test

Is ASTM D7490 the right test?

Interpreting surface free energy results

What the dispersive and polar parts tell you, and what they do not

Low total can mean contamination: ASTM notes that a low total surface tension can point to contamination, such as oils from handling or release agents.
High polar part can mean polar contamination: ASTM notes that a high polar part may signal polar residues. Check cleaning and rinse steps.
Match primer and topcoat: ASTM notes that matching the polar components of topcoats and primers is said to give better adhesion. Compare both layers with the same liquids and model.
Numbers depend on liquids and model: Fowkes, van Oss Chaudhury Good and OWRK give different splits. Compare results only when both match.
Expert perspective

Why two side view angles are an estimate

Droplet adhesion is three-dimensional. Two side-view angles give an estimate; the whole story is how the angle and the contact line vary all the way around the drop.

Dr. Alidad Amirfazli

Department of Mechanical Engineering, York University, Co-founder and Scientific Advisor, Droplet Lab

Common pitfalls in the test procedure

Honest limits of the method and of the Dropometer

Roughness or porosity, including on pressed pigment disks, gives apparent angles. ASTM notes this makes pigment comparisons hard.
Very clean high energy surfaces can spread water below 10°, which is under the Dropometer range. Report those as below 10°.
Contaminated or old test liquids shift both angles. Cap the bottles, store diiodomethane away from light and record the lot.
The Dropometer has no temperature or humidity control. Record room conditions and keep them steady.
The camera runs at 10 frames per second. That suits a reading at a fixed time, not millisecond spreading or absorption studies.
ASTM says the method is not designed as a QC or specification test. Any limits come from your own correlation study.
FAQ

Frequently asked questions

What does ASTM D7490 measure?

It measures the surface tension, also called surface free energy, of a solid coating, substrate or pigment. You measure the contact angles of one polar and one nonpolar liquid, then calculate the dispersive and polar parts. ASTM gives a working range of about 20 to 60 dyn/cm.

Is there a SEMI version of ASTM D7490?

We found none. ASTM publishes the method as D7490-13, reconfirmed by ASTM in 2022, under Committee D01 on paint and related coatings. Quote that designation in your reports unless your customer names a different document.

Can the Dropometer run ASTM D7490?

Yes. The Dropometer measures both contact angles with ±0.35° accuracy. D7490 needs a dispersive and polar split. The Dropometer software does Fowkes and van Oss Chaudhury Good. OWRK is not built in: users measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator.

Which two liquids does ASTM D7490 use?

One polar and one nonpolar liquid, each of known surface tension. Water and diiodomethane are a common pair. Use the liquids and property values the current edition specifies, and keep them fixed for every study.

Fowkes, OWRK or van Oss Chaudhury Good: which should I use?

Use the model your standard edition, SOP or customer names, and report it. Each model splits the same angles differently, so results from different models are not comparable. Fowkes and van Oss Chaudhury Good run in the Dropometer software; OWRK runs in our free calculator.

Can I use ASTM D7490 as a pass or fail QC test?

ASTM says the method is not designed as a quality control or specification test. Many teams use it in R&D and failure analysis, then set any QC limits from their own correlation study against peel, tape or print results.

Why measure two liquids instead of only water?

A water angle gives one number that mixes dispersive and polar effects. Two liquids let you separate them, which helps explain why a coating, ink or adhesive wets one surface and not another. See the surface energy measurement guide.

Legal note

This page summarises ASTM D7490 in our own words and does not reproduce the standard. Buy the current edition from ASTM before you write a procedure. Droplet Lab does not certify compliance. Your own method validation does.

View the official standard Book a 15 minute demo

How this page was created

Sources, review and tools

Transparency 4 checklist items
01

Sources

ASTM D7490-13(2022) listing; KRUSS ASTM D7490-13 overview; Droplet Lab Contact Angle to Surface Energy Calculator; Droplet Lab case study: fused silica and quartz R&D, the Dropometer product specification and Droplet Lab validation papers.

02

Drafting assistance

Drafted with Claude (Anthropic) from the sources listed, then reviewed by Droplet Lab.

03

What we did not do

We did not copy text from the standard. Buy the current edition for the full procedure.

04

Last checked

October 2026

Report a correction

Spotted an issue in this summary? Send a correction request and our team will review it.

Correction Request

We work hard to keep this page accurate and up to date. If you spot an error (wrong revision/year, missing requirement, incorrect interpretation, or broken link), tell us and we'll review it.

Contact us to report a correction

References

1. ASTM D7490-13(2022). store.astm.org/d7490-13r22.html
2. KRUSS ASTM D7490-13 overview. kruss-scientific.com/en/know-how/standards-and-norms/astm-d7490-13
3. Droplet Lab. Peer reviewed validation papers in Review of Scientific Instruments and Colloids and Surfaces A. dropletlab.com/validation/publications/
4. Droplet Lab. Dropometer product specification, 2026. dropletlab.com/products/dropometer/