Contents
Partially compliant

ASTM F22 standard test method for hydrophobic surface films by the water break test, and the contact angle alternative

ASTM F22 checks whether water sheets evenly over a cleaned surface or breaks into patches, a pass or fail sign of an oily or organic film. The Dropometer gets the same end result by a different route: it measures the water contact angle at chosen spots, from 10° to 175° with ±0.35° accuracy (product specification). A sessile drop contact angle is an alternative method, not the water break test the standard specifies; if a contract or customer requires an ASTM F22 result, run a correlation study on your own samples first.

What brings you here?

Who this is for
Metal finishers, aerospace, electronics and semiconductor plants, and anyone who cleans parts before priming, plating, anodizing or bonding.
Compliance tier
Partially compliant: the Dropometer detects hydrophobic films by water contact angle, an alternative to the visual water break test the standard specifies.
Measurement
Sessile drop water contact angle, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs at the cleaning line or in the lab.
Last updated
October 20, 2026
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Free one page checklist for water contact angle next to ASTM F22: what to prepare, the settings to lock, where to place drops and how to record readings below 10°. Made for cleaning and pretreatment benches.

Talk to an expert

Book a 15 minute demo on your cleaned parts

Tell us your parts, cleaning line and how you run the water break test today. We will measure live and tell you plainly which part of the job 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 F22
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 F22 and the Dropometer

Standard

ASTM F22-21, Standard Test Method for Hydrophobic Surface Films by the Water-Break Test, from ASTM Subcommittee E21.05. It is the 2021 revision and the active edition. Earlier editions date back to F22-65.

Compliance tier

Partially compliant. The Dropometer detects the same end result, a hydrophobic film, by measuring the water contact angle at chosen spots. It does not run the whole surface water break test, and very clean surfaces can read below its 10° range. A sessile drop contact angle is an alternative method, not the water break test the standard specifies; if a contract or customer requires an ASTM F22 result, run a correlation study on your own samples first.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°, 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 study run to ASTM F22 yet. A shared facility at Harvard University uses the Dropometer for water contact angle on silicone elastomers and saline contact angle on titanium implant discs before and after plasma treatment. Read the case study. A 2024 University of Utah thesis used it for contact angle on ski wax films. Read our analysis.

What it does not tell you

A raised angle or a water break shows that a hydrophobic film is present. Neither identifies the contaminant. Use a chemical method such as FTIR or XPS when you need to know what it is.

Executive summary: the water break test in coating quality control

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

ASTM F22 detects hydrophobic films on a surface with the water break test: water sheets evenly over a clean surface, and breaks into patches or beads where an oily or organic film remains. Metal finishers, aerospace, electronics and semiconductor plants use it for in-process verification after cleaning, as a fast pass or fail cleanliness check in quality control, before priming, conversion coating, powder coating, anodizing, plating or adhesive bonding. The Dropometer is partially compliant: it detects the same films by measuring the water contact angle, but it does not run the whole surface sheeting test, and it reads angles from 10° upward. A sessile drop contact angle is an alternative method, not the water break test the standard specifies; if a contract or customer requires an ASTM F22 result, run a correlation study on your own samples first.

ASTM states the water break test can detect molecular layers of hydrophobic contaminants, that it is not quantitative, and that rough or porous surfaces make it less sensitive. For a number, the standard itself points to sessile drop contact angle methods, and notes that a drop covers only a small area. That is where the Dropometer fits: a measured angle at the spots that matter, next to the visual check over the whole part. On rough parts, read about the Wenzel model of wetting on rough surfaces.

The Dropometer contact angle and surface energy kit runs on battery, so you can check parts at the cleaning line or in the lab. For the screening workflow, see silicone and invisible residue detection. A university shared facility uses the Dropometer for water contact angle on silicone elastomers and saline contact angle on titanium implant discs before and after plasma treatment. In a study of ski wax and friction on snow, a researcher used the Dropometer to measure the contact angle on hydrophobic wax films.

For background, read the electrical and electronics guide and the contact angle measurement guide.

Further reading: sample preparation and contamination control, our open dataset of Droplet Lab reference measurements, a classroom experiment that makes glass superhydrophobic with a flame and choosing a contact angle goniometer for industrial QA.

How a contact angle check fits next to the water break test

A water contact angle check next to the ASTM F22 water break test, step by step, in our own words

From a cleaned part to a recorded angle

These steps describe a water contact angle measurement on the Dropometer, run next to the water break test. They are not the ASTM F22 procedure and do not replace it. Buy the current edition and follow it for any result you report to the standard.

±0.35°

Contact angle accuracy

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

10° to 175°

Measuring range

Very clean metal or glass can read below 10°. Record those drops as below range.

About 2 min

Setup

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

1

Take the parts and protect them

Take production parts or clean witness panels from the line. Handle them by the edges with clean gloves or tongs. Note the cleaning step, the time it finished and the water break result if you ran it. See sample preparation and contamination control.

2

Set up the Dropometer

Place the base plate on a level bench, mount the phone and LED, and fill a clean syringe with water of the purity your procedure names. Dry the test area as your procedure describes, then lay the part flat on the sessile stage, test side up.

3

Place drops where films collect

Dispense the same drop volume at set positions: the centre, near edges and holes, at rack contact points and wherever the water broke. Do not touch the part with the needle, or you may leave a film yourself.

4

Capture and read the angle

Capture each drop at a fixed time after it lands. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. If the drop spreads below 10°, record it as below range.

5

Repeat across parts and batches

Read several drops per position and several parts per batch. Films from handling, racks or drying often sit in one area, so one drop is not enough.

6

Record and correlate

Record the mean, spread, positions, cleaning step, time since cleaning, water break result and room conditions. Compare the mean with your accept limit. State that these are contact angle results, not ASTM F22 water break results.

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° (Dropometer product specification).

Read the validation papers

Customer evidence

We have no published client study on the water break test yet. A shared facility at Harvard University uses the Dropometer for water contact angle on silicone elastomers and saline contact angle on titanium implant discs before and after plasma treatment.

Read the case study

Set your angle limit from water break free test results

ASTM F22 · hydrophobic films · cleaning process control

ASTM F22 is a pass or fail test and gives no contact angle that matches a water break free surface (source: ASTM F22-21 listing). So set your accept limit from your own correlation study. Run the water break test and the contact angle on the same parts, cleaned well and cleaned badly, then pick the angle that separates passing parts from failing ones.

Check where your limit sits against the Dropometer range of 10° to 175°. If your limit is above 10°, a drop that spreads below 10° still sits under the limit: record it as below range and accept. If you must report exact values on very clean metal or glass below 10°, use a goniometer rated for low angles for that part of the work.

ASTM notes that a contact angle drop covers a small area. Place drops where films tend to collect, such as edges, holes, rack contact points and handled areas, and keep the water break test for the whole part. Repeat the study when you change the cleaner, rinse water, alloy, surface finish or the time between cleaning and testing.

Example output

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

Example: aluminium panels after different cleaning and handling steps

Panel Water break result Drops (n) Mean angle (°) Std dev (°) Decision
Solvent wipe onlyBreaks into patches548.22.4Reclean
Alkaline clean and rinseBreak free512.61.0Accept
Alkaline clean, then handled without glovesBreaks at the handled area535.16.8Reclean and review handling
Alkaline clean and deoxidiseBreak free5Below 10 (below range)n/aAccept: under the 20° limit, value not given
Alkaline clean, then 24 h in open shop airSmall breaks near the edges524.31.9Above limit: reclean or store covered

How to read this table

Each row is the mean of five drops of deionised water at set positions. The water break column is the visual result on the same panel. The decision column uses an example accept limit of 20° or lower, set from a correlation study against the water break test. The deoxidised panel read below 10°, outside the Dropometer range, so its value is not given.

Example output chart

The same example data as the table, plotted against the example accept limit. The deoxidised panel is left out because it read below 10°.

Bar chart of example water contact angles on aluminium panels after four cleaning and handling steps, with a 20 degree accept limit and the 10 degree bottom of the Dropometer range marked

Example data, not measured results.

Business impact on powder coating quality control and adhesive bonding

What changes when a measured angle sits next to the water break test

Metric Before Dropometer With Dropometer Results
How the check is made Water break test, judged by eye Water contact angle read from the drop image, next to the water break test No published benchmark
Result format Pass or fail An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Area covered The whole wetted surface Small spots, one drop each, at positions you choose ASTM F22-21 notes contact angle devices cover a small area
Reported ASTM F22 result Water break test Still needs the water break test ASTM F22 scope

See the measurement on your own parts

Bring two parts: one that passed the water break test and one that did not. We will measure both live.

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ROI estimate

Estimate the cost of the coating, plating and bonding 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 for the contact angle check

Lock these before you compare angles between shifts, lines or sites

Parameter Recommended Setting Technical Rationale
Method Sessile drop water contact angle, reported as an alternative method ASTM F22 specifies the visual water break test. Its public summary names contact angle methods for quantitative wetting.
Test liquid Deionised or distilled water, the same grade as your water break test Impure water carries its own films and gives false readings.
Drop volume Fixed for every drop A changing volume adds spread that is not about contamination.
Reading time Fixed for every drop Water keeps spreading on a clean surface, so the time must not vary.
Positions Set positions per part, including edges, holes and rack points A drop covers a small area, and films are often uneven.
Measuring range 10° to 175°; record lower readings as below range Dropometer product specification. Very clean metal or glass can spread below 10°.
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.
Time since cleaning Fixed and recorded Clean surfaces pick up films from the air, so the angle can rise with storage time.
Environment Record room temperature and humidity The Dropometer runs at 10 to 45 °C and has no temperature or humidity control.

Is ASTM F22 the right test?

Pick the method by the question you need answered

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

A measured number at the spots that matter

Signals:

You want an angle per part or batch to trend cleaning, and your accept limit is above 10°.

Rule-out:

Use the water contact angle on the Dropometer. It is an alternative method, not the ASTM F22 water break test, so correlate it with your water break results first. For glass, see ASTM C813.

A pass or fail over the whole part

Signals:

You need a fast check that water sheets over every surface before plating, priming or bonding, or a customer names ASTM F22.

Rule-out:

Run the ASTM F22 water break test. It needs clean water and a trained eye, not the Dropometer. Use the contact angle to add a number at chosen spots.

Parts you cannot flood with water

Signals:

The part cannot be immersed or doused, or water would be trapped in joints or assemblies.

Rule-out:

ASTM points to the atomizer test, ASTM F21. A few sessile drops on the Dropometer can also check accessible spots.

Why a coating or adhesive fails

Signals:

You need polar and dispersive surface free energy, not only whether a film is present.

Rule-out:

Use a two liquid method such as ASTM D7490. The Dropometer measures the angles for it.

Decision tree at a glance

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

Decision tree for choosing between a water contact angle on the Dropometer, the ASTM F22 water break test, the ASTM F21 atomizer test and a two liquid surface energy method

Is ASTM F22 the right test?

Interpreting results

What the angle tells you, and what it does not

Higher angle, more hydrophobic film: A clean metal or glass surface wets well. Oils, silicones and other organic films make water bead up, so the angle rises and the water film breaks.
Spread across the part matters: A good mean with one high position points to a handling, rack or drying problem in that area.
Clean surfaces do not stay clean: Record cleaning time and test time. Parts left in open air can read higher hours later than at the line, depending on the level of airborne contaminants and the duration of exposure.
Angle is not identity: A raised angle shows a film is present. It does not say what the film is or where it came from.
Expert perspective

Why a film a few molecules thick changes how water wets

What a liquid responds to is only the outermost few ångström of a surface: the skin, not the bulk. Change that skin and you change the wetting, even if the material underneath is identical.

Dr. Alidad Amirfazli

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

Common pitfalls and limits of the water break test

Honest limits of the method and of the Dropometer

A sessile drop contact angle is an alternative method, not the water break test ASTM F22 specifies. Do not report angles as F22 results without a correlation study on your own samples.
Each drop covers a small spot. A film can sit between your drops, so keep the water break test for the whole part.
Very clean metal or glass can read below 10°, outside the Dropometer range. Record it as below range, or use a goniometer rated for low angles.
ASTM notes that very rough or porous surfaces make the water break test much less sensitive. Rough surfaces also change the contact angle, so set limits per surface finish.
Skin oils, powdered gloves, interleaf paper and plastic packing all leave films. Handle parts by the edges with clean tools.
The Dropometer has no temperature or humidity control, and its camera runs at 10 frames per second. Read at a fixed time and record room conditions.
FAQ

Frequently asked questions

What does ASTM F22 measure?

It detects hydrophobic films on a surface with the water break test. Water sheets evenly over a clean surface and breaks into patches or water droplets where an oily or organic film remains, a film that can interfere with later surface treatments such as priming. ASTM describes it as a fast, non destructive pass or fail check that is not quantitative.

Can the Dropometer run ASTM F22?

In part. It gets the same end result, whether a hydrophobic film is present, by measuring the water contact angle at chosen spots. It does not run the visual sheeting test over the whole part. A sessile drop contact angle is an alternative method, not the water break test the standard specifies; if a contract or customer requires an ASTM F22 result, run a correlation study on your own samples first.

What water contact angle matches an ASTM F22 water break free surface?

No published angle does. ASTM F22 is a pass or fail test and its public summary gives no contact angle threshold. Run both tests on the same parts, cleaned well and cleaned badly, and set your accept limit from that data. See silicone and invisible residue detection for a screening workflow.

Why does ASTM F22 mention contact angle methods?

Because the water break test gives no number. The public ASTM F22 summary says sessile drop contact angle methods, such as ASTM C813 and ASTM D7490, can be used where quantitative wetting data is needed. It also notes that a drop covers a small area, so many plants use both.

When should I use ASTM F21 instead of ASTM F22?

When the part cannot be immersed or doused with water, or water would be trapped in joints. ASTM points to the atomizer test, ASTM F21, for those surfaces. A few sessile drops can still check accessible spots.

Does the water break test work on rough or porous surfaces?

Less well. ASTM notes that very rough or porous surfaces can make the test much less sensitive. Roughness also changes the contact angle, as the Wenzel model describes, so set limits for each surface finish.

Can the Dropometer measure very clean metal or glass?

Down to 10°. Its range is 10° to 175° with ±0.35° accuracy (product specification). Very clean surfaces can spread below 10°. If your limit is above 10°, record those drops as below range and accept. If you need the exact low value, use a goniometer rated for low angles.

Legal note

This page summarises ASTM F22 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: it detects hydrophobic films by water contact angle, an alternative to the water break test the standard specifies. 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 F22-21 listing; ASTM F22-13 listing (historical); Nimonik: ASTM F22-21 summary (December 2021, 5 pages); DIN Media listing: ASTM F22, 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 F22-21. store.astm.org/f0022-21.html
2. ASTM F22-13 listing (historical). store.astm.org/f0022-13.html
3. Nimonik: ASTM F22-21 summary (December 2021, 5 pages). standards.nimonik.com/products/astm/f22/
4. DIN Media listing: ASTM F22. dinmedia.de/en/standard/astm-f-22/349539480
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/