Contents
Partially compliant

ASTM D8597-24: surface wettability of coatings, substrates and pigments by contact angle measurement using portable goniometers

ASTM D8597 checks how well coatings, substrates and treated parts wet by reading the contact angle with a portable goniometer. The Dropometer runs the sessile drop measurement and the two liquid surface energy step with an accuracy of ±0.35°. It is portable, not handheld, so readings straight on large or fixed parts need a handheld goniometer or witness coupons.

What brings you here?

Who this is for
Paint shops, bonding and sealing lines, coating makers and plastics moulders who check surfaces before painting or bonding.
Compliance tier
Partially compliant: the Dropometer runs the sessile drop contact angle and surface energy step, but it is portable, not handheld, so it does not read straight on large or fixed parts.
Measurement
Sessile drop contact angle, 10° to 175° range, ±0.35° accuracy; surface free energy up to 100 mN/m (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs at the line or in the lab.
Last updated
October 20, 2026
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Free one page checklist for ASTM D8597: what to prepare, the settings to lock, how to present parts or coupons and what to record. Made for paint shop, bonding and coating QC benches.

Talk to an expert

Book a 15 minute demo on your parts

Tell us your part, coating or surface treatment and your current check. We will show the measurement live and tell you plainly which part of ASTM D8597 the Dropometer covers and which it does not.

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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
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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.
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Verified against ASTM D8597
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: ASTM D8597-24 standard test method and the Dropometer

Standard

ASTM D8597-24, Standard Test Method for Surface Wettability of Coatings, Substrates, and Pigments by Contact Angle Measurement Using Portable Goniometers, from ASTM International Subcommittee D01.23. It began as work item WK72334. Brighton Science, a maker of handheld goniometers, helped develop it.

Compliance tier

Partially compliant. The Dropometer deposits the drop and reads the sessile drop contact angle, and it calculates surface free energy from two or more liquids. The standard's scope names a portable, handheld device that measures on the part. The Dropometer is a portable bench unit, so large or fixed parts need a fixture, coupons or a handheld goniometer.

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

We have no published client paper or case study on this method yet. For the workflow on parts too big for a lab stage, see surface energy and wetting checks on large parts.

What it does not tell you

ASTM notes that contact angle cannot measure surface tension directly and can only help estimate surface free energy. It shows that something changed on the surface, not what. Use a technique such as infrared spectroscopy to find the cause.

Executive summary

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

ASTM D8597 measures the wettability of coatings, substrates and pigments by reading the contact angle of a sessile drop with a portable goniometer, so the check can run on the production floor. Paint shops, bonding and sealing lines, coating makers and plastics moulders use it to control cleaning, surface treatment and storage before painting or bonding. The Dropometer is partially compliant: it runs the sessile drop contact angle with ±0.35° accuracy and the two liquid surface energy step, but it is a portable bench instrument, not a handheld device you place on the part.

The standard supplements the device maker's own instructions and is not intended to replace them. Common test liquids are water, diiodomethane, ethylene glycol and formamide. Water shows polar character, and a second, mainly dispersive liquid lets you split surface free energy into polar and dispersive parts, as ASTM D7490 describes. The angle itself follows the Young equation.

The Dropometer contact angle and surface energy kit runs on battery, so you can take it to the line and measure parts or coupons that fit its stage or a fixture. The large parts workflow is in surface energy and wetting checks on large parts. Fowkes, van Oss Chaudhury Good and Equation of State models are built into the software. OWRK is not built in: measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator.

For background, read the paint guide, the surface energy measurement guide and why contact angle matters for coatings and adhesives QC.

Further reading: reproducible surface energy calculation, an experiment on surface free energy with multiple liquids, surface free energy reference values for common polymers and how the Dropometer compares with the KRUSS Mobile Surface Analyzer.

How the Dropometer fits the test method for surface wettability

The ASTM D8597 measurement, step by step, in our own words

From part or coupon to a recorded angle and surface energy

These steps outline the procedure and show where the Dropometer differs from a handheld goniometer. They do not replace the standard or the instrument instructions it builds on. Buy the current edition and follow its specimen, liquid and reporting rules.

±0.35°

Contact angle accuracy

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

±0.03 mN/m

Surface energy accuracy

Up to 100 mN/m, from the Dropometer product specification.

About 2 min

Setup

Base plate, phone holder, LED and syringe. Battery for about 8 h, no PC needed.

1

Pick the zones and the liquids

Mark the zones you need to check, such as treated, masked and edge areas. Choose water for a single liquid check, or water plus diiodomethane when you need surface free energy. Diiodomethane and formamide raise safety concerns, so handle them under your own lab rules.

2

Present the part to the Dropometer

Bring the part or a cut section to the stage, hold the Dropometer on a fixture at the part, or measure witness coupons treated alongside it. Custom holders are available on request. The test area must be level enough to hold a sessile drop.

3

Place the drop

Dispense the drop volume your procedure sets, with the manual dropper or the automatic dropper. Keep the volume the same for every drop. Do not touch the surface with the needle or your fingers.

4

Capture and read the angle

Capture the drop at a fixed reading time. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. For advancing and receding angles, add or withdraw liquid through the needle.

5

Repeat, then calculate surface energy

Place several drops in each zone with each liquid. Calculate surface free energy in the software with Fowkes, van Oss Chaudhury Good or Equation of State. OWRK is not built in: run the angles in the free Contact Angle to Surface Energy Calculator.

6

Record and report the deviations

Record the mean and spread per zone, the liquids, drop volume, reading time, model and room conditions. State how the part was presented: on the stage, on a fixture or as witness coupons, since the standard describes a handheld device.

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.

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 paper or case study on ASTM D8597 yet. The large parts use case shows how to bring the measurement to parts that do not fit a lab goniometer: at the stage, on a fixture or with witness coupons.

Read the use case

Set limits for each coating, substrate and pigment

ASTM D8597 · wettability · paint, bonding and coating QC

ASTM D8597 publishes no pass or fail angle. Its significance section notes that a water contact angle below about 45° points to a hydrophilic surface, and that easily wetted surfaces are less prone to poor adhesion and defects such as cratering, pin holing, orange peel and fish eyes (source: ASTM D8597-24 summary).

ASTM also notes that the angle is very sensitive to surface composition, history, the presence of contaminants and roughness, which makes it useful for mapping treatment uniformity across a part. So set your accept limit from a correlation study. Measure parts that painted or bonded well and parts that failed, with the same liquids, drop volume and reading time, then compare with your adhesion test.

If you report surface free energy, keep one model and one liquid pair for the whole study. See reproducible surface energy calculation. Repeat the study when you change cleaner, treatment, resin or coating. Contact angles can also track ageing after environmental or wear exposure, for example on water repellent coatings.

Example output

Example data for illustration only. These are not measured results. Your own parts, treatment, liquids and limits decide the numbers.

Example: flame treated polypropylene witness coupons before painting

Sample Water angle (°) Diiodomethane angle (°) Total SFE (mN/m) Polar part (mN/m) Decision
Coupon, upper zone72.444.144.46.9Accept
Coupon, centre zone74.845.642.86.1Accept
Coupon, lower zone88.652.335.12.2Hold the parts, check the flame treater
Untreated reference101.556.231.00.2Reference only

How to read this table

Each angle is the mean of five drops per liquid. Surface free energy uses water and diiodomethane with OWRK, which is not built in: the angles were run in the free Contact Angle to Surface Energy Calculator. The decision column uses an example accept limit of 40 mN/m or higher, set from a paint adhesion study.

Example output chart

The same example data as the table: total surface free energy per sample against an example accept limit of 40 mN/m.

Bar chart of example total surface free energy on three zones of flame treated polypropylene coupons and an untreated reference, with the lower zone below a 40 mN/m example accept limit

Example data, not measured results.

Business impact: why a measured wettability check is useful

What changes when the wettability check runs at the line

Metric Before Dropometer With Dropometer Results
Where the check runs Lab goniometer, parts sent off the line At the line on parts, sections or coupons, on battery for up to 8 h Dropometer product specification
Result format Dyne pens or a water break test, read by eye An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Surface free energy Lab only, often sent out Two liquid result at the line, ±0.03 mN/m accuracy Dropometer product specification
Readings straight on large or fixed parts Handheld goniometer Still needs a handheld goniometer, a fixture or witness coupons ASTM D8597 scope

See the measurement on your own parts

Bring two parts or coupons: one that painted or bonded well and one that did not. We will measure both live.

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ROI estimate

Estimate the cost of the paint and bond failures this test can catch

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.

Method settings to lock before you measure

Lock these before you compare results between shifts or sites

Parameter Recommended Setting Technical Rationale
Test liquids Water; add diiodomethane for surface free energy The standard lists water, diiodomethane, ethylene glycol and formamide as common choices. Surfactant or solvent solutions can be used if they suit the instrument.
Drop type Sessile drop, static angle; advancing and receding if needed The method is based on a sessile drop on the solid surface.
Drop volume As your procedure and the standard specify, fixed for every drop A changing volume adds spread that is not about the surface.
Reading time One fixed time after placement, the same for every drop Drops 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, van Oss Chaudhury Good or Equation of State in the software; OWRK is not built in, so run it in the free calculator Results differ between models, so compare values only within one model and one liquid set.
Part presentation On the stage, on a fixture or as witness coupons; report which The Dropometer is portable, not handheld. The standard describes a handheld device.
Environment Record room temperature and humidity The Dropometer runs at 10 to 45 °C and has no temperature control.

Is ASTM D8597 the right test?

Pick the method by the question you need answered

Start: What do you need to know about the surface before painting or bonding?

Wettability on parts or coupons that fit

Signals:

You want a measured angle per zone on parts, cut sections or witness coupons that sit on the stage or a fixture, to check cleanliness or treatment.

Rule-out:

Use ASTM D8597, this page. The Dropometer is partially compliant and runs the sessile drop measurement.

Readings straight on a large or fixed part

Signals:

You need to press the instrument onto a car body, aircraft panel or vertical surface without cutting it.

Rule-out:

Use ASTM D8597 with a handheld goniometer. Or treat witness coupons alongside the part and measure them on the Dropometer.

Polar and dispersive surface free energy

Signals:

You need to know why paint or adhesive fails, not just whether the surface wets.

Rule-out:

Use ISO 19403-2 or ASTM D7490. The Dropometer measures the angles for both.

Advancing angle only

Signals:

Your specification calls for the advancing contact angle on a coating, substrate or pigment disk.

Rule-out:

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

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 D8597 on the Dropometer, a handheld goniometer for large parts, ISO 19403-2 or ASTM D7490 surface free energy and ASTM D7334 advancing contact angle

Is ASTM D8597 the right test?

Interpreting contact angles on coatings, substrates and pigments

What the angle and surface energy tell you, and what they do not

Lower water angle, easier wetting: A lower water angle means the surface is easy to wet. ASTM links such surfaces with good adhesion and appearance and fewer coating defects.
Spread between zones matters: A good mean with one high zone points to uneven cleaning, treatment or contamination in that area.
Two liquids explain more than one: Water tracks polar groups and diiodomethane tracks dispersive character. Together they split surface free energy into both parts.
Angle is not adhesion: A low angle shows the surface wets. It does not prove a paint or adhesive will bond, or say what contaminated the surface.
Expert perspective

Why the contact angle tracks paint and bond readiness

Not all contact-angle measurements are created equal: the right method depends on the application. A sessile drop and a tilted plate can give very different, and equally correct, numbers.

Dr. Alidad Amirfazli

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

Limits of contact angle measurement using portable goniometers

Honest limits of the method and of the Dropometer

The Dropometer is portable, not handheld. Large or fixed parts need a fixture, a cut section or witness coupons.
Vertical and overhead surfaces cannot hold a sessile drop. Measure a level area or a coupon instead.
Roughness is a factor: rough, curved or absorbent surfaces give an apparent angle that reflects texture as well as chemistry.
Surface free energy values change with the model and liquid pair. Keep both fixed within a study.
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 studies.
FAQ

Frequently asked questions

What does ASTM D8597 measure?

It measures the contact angle of a liquid drop on a coating, substrate or pigment with a portable goniometer, to judge how well the surface wets. With two or more liquids, contact angles can be used to estimate surface free energy, as ASTM D7490 describes.

Can the Dropometer run ASTM D8597?

In part. The Dropometer deposits the drop and reads the sessile drop contact angle with ±0.35° accuracy, and it calculates surface free energy from two or more liquids. It is a portable bench instrument, not a handheld one. For readings straight on large or fixed parts, use a handheld goniometer, or measure witness coupons on the Dropometer.

Does ASTM D8597 require a handheld goniometer?

The scope describes a portable, handheld device that deposits the liquid and takes the reading. ASTM's announcement also mentions robotically mounted units that measure on finished parts. Brighton Science, KRUSS and DataPhysics all make portable or handheld units. Check which form your customer's specification expects before you write the procedure.

Which test liquids does ASTM D8597 use?

The choice depends on what you need to know. The standard lists water, diiodomethane, ethylene glycol and formamide as common choices. Water alone gives a wettability check. Water plus diiodomethane lets you split surface free energy into polar and dispersive parts. OWRK is not built into the Dropometer software: measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator.

How is ASTM D8597 different from ASTM D7334?

Both read a sessile drop contact angle on coatings, substrates and pigments. D7334 covers the advancing angle with any goniometer. D8597 covers measurement with portable goniometers, so the check can run on the production floor. See ASTM D7334.

What contact angle is good enough for painting or bonding?

ASTM D8597 publishes no pass or fail value. It notes that a water angle below about 45° indicates a hydrophilic surface. Set your own limit from parts that painted or bonded well and parts that failed, measured the same way.

Legal note

This page summarises ASTM D8597 in our own words and does not reproduce the standard. Buy the current edition from ASTM before you write a procedure. The Dropometer is partially compliant with this method. Droplet Lab does not certify compliance. Your own method validation does.

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How this page was created

Sources, review and tools

Transparency 4 checklist items
01

Sources

ASTM D8597-24 listing (ASTM store); ASTM news: new paint standard assesses wettability (2025); ASTM news: proposed coating wettability standard, WK72334 (2020); ASTM D8597-24 scope sections and keywords (en-standard.eu), 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

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References

1. ASTM D8597-24. store.astm.org/d8597-24.html
2. ASTM news: new paint standard assesses wettability (2025). astm.org/news/new-paint-standard-assesses-wettability
3. ASTM news: proposed coating wettability standard, WK72334 (2020). astm.org/news/coating-wettability-ja20
4. ASTM D8597-24 scope sections and keywords (en-standard.eu). en-standard.eu/astm-d8597-24-standard-test-method-for-surface-wettabil
5. Droplet Lab. Peer reviewed validation papers in Review of Scientific Instruments and Colloids and Surfaces A. dropletlab.com/validation/publications/
6. Droplet Lab. Dropometer product specification, 2026. dropletlab.com/products/dropometer/