Contents
Hydrophobicity and Self Cleaning

Hydrophobic Coating and Ceramic Coating Testing: Measure Hydrophobic Performance, Find Out Why a Ceramic Coating Failed, and Set Coating Maintenance for a Longer Lifespan

Water beading is the visible sign that a coating works, but it cannot tell a worn coating from a dirty one. Measure water contact angle and sliding angle, before and after washing, decontamination and weathering, to verify hydrophobic properties with numbers and decide when a coating needs cleaning, a top up or a recoat.

Who this is for: Formulators, installers and quality teams working with ceramic coatings and other hydrophobic or oleophobic coatings and surface treatment products.

Where it fits: Formulation screening, batch and install sign off, durability testing, and coating maintenance decisions.

What it does not do: It does not measure gloss, hardness or scratch resistance, and it does not replace weathering or field tests.

Method
Sessile drop contact angle and tilt stage sliding angle
Standard
Fully compliant with ISO 19403-2 and ISO 19403-6
Setup
About 2 minutes
Book a 15 minute demo Request a quote
Water beads of many sizes on a black hydrophobic coated surface
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
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
Why it matters

How hydrophobic coatings change with exposure

147° to 121°

water contact angle of a polysilazane and silica coating before and after 120 hours of artificial weathering.

Pérez-Gandarillas et al., Coatings 13(3):537 (2023)

115° to under 50°

fall in water contact angle of one coating on glass after 2,500 hours of xenon arc weathering, while the same coating stayed above 100° on polycarbonate after 3,000 hours.

Lu, Zhao and Hellerman, Scientific Reports 14:8066 (2024)

130° to 143°

range of water contact angles a university lab measured with the Dropometer across electrospun fibre mats, enough to rank each recipe.

University of Calgary, Macromolecular Rapid Communications 45:2400403 (2024)

Sources: L. Pérez-Gandarillas et al., Highly hydrophobic organic coatings based on organopolysilazanes and silica nanoparticles: evaluation of environmental degradation, Coatings 13(3):537, 2023; S. Lu, Y. Zhao, E. A. P. Hellerman, UV durable self cleaning coatings for autonomous driving, Scientific Reports 14:8066, 2024; University of Calgary case study, Macromolecular Rapid Communications 45:2400403, 2024 (a customer publication that used the Dropometer). Figures come from these sources, not from Droplet Lab measurements.

Quick reference

What this hydrophobic coating check does and what it does not

A quick reference for coating and quality teams checking fit before reading further.

Evidence Box

Problem this solves

Hydrophobic and ceramic coatings that lose water repellency, or look like they failed when they are only contaminated.

Standards

Fully compliant with ISO 19403-2 (surface free energy) and ISO 19403-6 (dynamic contact angle); partially compliant with ISO 19403-7 roll off, up to 60° tilt.

Peer reviewed method

The Dropometer drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, in Review of Scientific Instruments and Colloids and Surfaces A.

Customer case studies

A Fortune Global 500 aerospace and defense coating team uses the Dropometer for oleophobic coatings; a University of Calgary lab ranked fibre mats from 130° to 143°.

Customer publication

Researchers used the Dropometer to track how water contact angle on quaking aspen leaves developed over time after defoliation.

Honest limit

Contact angle and sliding angle show water repellency. Gloss, hardness, scratch and chemical resistance need other tests.

Who this is for

What hydrophobic coating question are you trying to answer?

Pick the card closest to your role. Each one points to the part of this page that answers it.

Coating formulator

You need to know which formulation keeps its hydrophobic properties longest, with data on optimal performance and longevity. Contact angle and sliding angle after each weathering, wash or abrasion step rank candidates with numbers instead of photos of water beading.

Test on the customer's substrate; the same coating can last very differently on glass and polycarbonate.

Installer or professional detailer

A customer says the ceramic coating failed. A reading before and after a decontamination wash shows whether the coating is worn or only covered by road film, and gives you and vehicle owners data instead of opinions, turning maintenance tips into readings you can show.

Measure after a proper wash; a dirty coating reads like a failed one.

Industrial coating QC

Customers ask for proof of quality on hydrophobic or oleophobic coatings. Contact angle with water and a second liquid, plus sliding angle, gives a release record for each batch.

Set gates from your own reference coating and field results, not a value from a data sheet.
Fit check

Is this the right check for your coating?

It helps when water repellency is the property you sell or specify. It helps less when the question is appearance or mechanical durability.

Good fit if

You make, apply or specify a ceramic coating or other hydrophobic coating.
You need to tell coating degradation from contamination.
You test performance after washing, UV, weathering or abrasion.
Drops bead but do not roll off, and you need to measure why.
You need a numeric release check for each batch or install.

Less relevant if

You need gloss, colour or haze measurements.
You need hardness or scratch resistance ratings.
The surface is too curved or rough to hold a drop, and coupons are not possible.
You only need a quick visual bead check for a consumer.
Summary

How to verify hydrophobic coating performance

The answer in under a minute.

Measure water contact angle for how strongly the coating repels water, and sliding angle for whether drops roll off. Test fresh panels, then after washes, decontamination and weathering. If a low reading recovers after a proper wash, the coating was contaminated; if it stays low, the coating has degraded and needs a recoat.

The Dropometer contact angle kit with its tilt stage runs both checks; our contact angle measurement guide and sliding angle measurement guide explain the methods. Surface free energy follows ISO 19403-2. A Fortune Global 500 aerospace and defense coating team uses it for oleophobic coatings, and researchers used it to study superhydrophobic aspen leaves. Our consumer products guide and automotive guide cover the wider context.

Expert Quote

Expert perspective on repellency and roll off

“

Repellency and mobility are not the same thing: a high contact angle says a drop is repelled, but whether it rolls off is a separate question; the two can even be mutually exclusive.

Dr. Alidad Amirfazli

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

The problem

Why a ceramic coating loses its ability to repel water

A ceramic coating or other hydrophobic coating gives a surface protection and makes water bead and roll off, which makes the finish easier to wash and slows water spots. That hydrophobic effect does not last forever. UV rays and weathering break down the outer layer: in one study a polysilazane and silica coating fell from about 147° to about 121° after 120 hours of artificial weathering. Abrasive polishing, brushes in automatic car washes and harsh alkaline or acidic cleaners wear it further. Bird droppings and tree sap can etch into the coating if left, and studies on automotive clearcoats found bird droppings among the most damaging biological contaminants. Often the coating is not worn at all. Road film, brake dust, mineral water spots and old soaps sit on top and hide its hydrophobic properties, so a coating might look failed when it only needs a deep clean. Water beading by eye cannot tell these apart, or say when the coating needs maintenance. Contact angle and sliding angle can.

Water sheets or clings instead of beading after a few months.
Drops bead but stay on the surface instead of rolling off.
Some panels or areas where the coating behaves differently from the rest.
Slickness and ease of washing fade between maintenance washes.
A customer reports the ceramic coating failed, and nobody can prove why.
Troubleshooting

Why hydrophobic performance drops and how to fix it

Why:

  • Road film, brake dust, grime, mineral water spots and old maintenance products cover the coating and mask its hydrophobicity.

How to detect:

  • Contact angle is low but recovers after a pH neutral wash and decontamination.

Corrective action:

  • Set a regular maintenance routine: use a dedicated pH neutral car shampoo, a water spot remover only where needed, and periodic decontamination. No recoat needed.

Why:

  • UV and moisture slowly break down the outer layer of the coating.

How to detect:

  • Contact angle stays low and sliding angle stays high after a proper deep clean.

Corrective action:

  • Recoat, and compare formulations under the same weathering cycles, for example to ASTM D7869 or SAE J2527 xenon arc exposure.

Why:

  • Brushes, dirty wash mitts, using a clay bar too often and abrasive polishing strip away the coating.

How to detect:

  • Readings fall most on high wear areas such as door handles and lower panels.

Corrective action:

  • Use a clean microfiber mitt, avoid abrasive products, and measure before and after any polishing.

Why:

  • Strong alkaline cleaners, a slightly acidic wash used to remove water spots, and some soaps attack the coating or leave residue on it.

How to detect:

  • Readings drop after a change of wash product, then partly recover with a plain water rinse.

Corrective action:

  • Test maintenance products on coated panels before calling them ceramic coating safe. Rinse thoroughly after any cleaner.

Why:

  • A high contact angle with high hysteresis means drops bead but stay put, so the surface does not shed water.

How to detect:

  • Contact angle is high but sliding angle is high too, or drops do not move by 60°.

Corrective action:

Adjust the formulation or topcoat for lower hysteresis. Our lotus effect glossary entry explains why roll off needs low adhesion.

Why:

  • Polish oils, panel wipe residue, a coating not spread evenly or too short a cure stop the coating bonding to the surface.

How to detect:

New installs read low or patchy across a panel. For reference data, see our client wetting measurements dataset.

Corrective action:

  • Lock prep, panel wipe and cure time, apply with a clean microfiber applicator, and measure each install before hand over.

Not sure whether your coating failed?

Send a coated panel that still works and one that does not, and we will compare them on a call.

Book a 15 minute demo
Quality records

What a hydrophobic coating test record contains

Each test produces a record you can file with the batch, install or warranty claim. These records can feed into your existing quality records under ISO 9001, IATF 16949 or your own process.

Coating and batch

Product, batch, substrate and finish, application method and cure.

Wear history

Washes, decontamination, polishing, UV hours or abrasion cycles completed.

Method settings

Probe liquids, drop volumes, reading time, tilt rate and spots per panel.

Readings

Contact angle median and spread, sliding angle, and any drop that did not slide by 60°.

Decision

Pass, clean and retest, or recoat, with the operator and date.

Drop images

Automatic edge and baseline detection gives the same reading from the same image, so a reviewer can recheck any result.

Measurements

What to measure on a hydrophobic or ceramic coating

Repellency

Static water contact angle

Why it matters: It shows how strongly the hydrophobic surface repels water.

How to interpret: Compare with your reference coating and the uncoated substrate, measured the same day. There is no universal pass value; set gates from your own references.

When it is not enough: It does not show whether drops roll off.

Roll off

Sliding angle on a tilt stage

Why it matters: It shows whether drops roll off and carry dirt with them.

How to interpret: Lower is easier roll off. Compare at the same drop volume, and record no movement by 60° as 60° or more.

When it is not enough: Drop volume changes the result, so lock it.

Pinning

Advancing and receding contact angles

Why it matters: Their difference, the hysteresis, explains why some drops bead but do not move.

How to interpret: Lower hysteresis usually means drops slide at a lower tilt.

When it is not enough: On some surfaces the onset of motion is hard to capture.

Oleophobic

Contact angle with an oil or second liquid

Why it matters: It shows oil repellency and gives surface free energy with water.

How to interpret: Use the same liquids every time, and compare with the reference coating.

When it is not enough: Different liquid sets give different energy values.

Durability

Retention after wear and a clean

Why it matters: It separates true coating degradation from contamination, and shows coating life under washing, UV and abrasion.

How to interpret: Measure as found, then after a decontamination wash; only the second reading shows the coating itself.

When it is not enough: Lab cycles only approximate real wear; confirm in the field.

Validation

Validated measurement approach for hydrophobic coatings

How the Dropometer itself has been validated, and where customers have used it.

Peer reviewed method

The Dropometer drop shape method is published in Review of Scientific Instruments and Colloids and Surfaces A. Contact angle was validated against a KRUSS DSA100E, with a published accuracy of 0.35°.

See the validation papers

Customer evidence on hydrophobic coatings

A coating team at a Fortune Global 500 aerospace and defense company added oleophobic coatings, and its customers wanted contact angle with more than one liquid as proof of quality. The team chose the Dropometer in 2023, kept that choice through two years of delays, and bought it in 2025.

Read the case study
QC Protocol

How to verify hydrophobic coating performance

Six steps for one coating and substrate. Repeat for each new formulation, substrate or maintenance product.

2

Baseline the substrate and a reference

Measure the uncoated substrate and your reference coating. Our experiment on superhydrophobic surfaces on glass shows the method on a simple surface.

3

Measure fresh panels

Measure contact angle and sliding angle once the coating is fully cured.

4

Apply wear steps

Run washes, decontamination, UV or abrasion cycles, rinse thoroughly, dry and measure again after each set.

5

Clean and retest any low reading

A reading that recovers after a pH neutral wash was contamination; one that stays low is coating degradation.

6

Decide and trend

Pass, clean and retest, or recoat, and trend readings by batch, installer and maintenance product.

We completed our gage R&R study on the unit and it performed very well.

Brandon Barbee

Corporate Quality Engineer, Zeus Industries, Polymer Manufacturing

Download the hydrophobic coating performance SOP

A two page SOP you can adapt for your coating and substrate, with the method lock, gate setting, a clean and retest step, a troubleshooting table and a record sheet.

Sliding angle measurement with the Dropometer

Example output

Example ceramic coating maintenance log

Example data only. Your values and gates will differ and must come from your own references.

How to read this log

Example gates: contact angle at or above 95° and sliding angle at or below 30°. After 20 hand washes the coating was still performing like new within the gates. After road exposure the panel looked failed, but it recovered after a decontamination wash, so it only needed cleaning. After machine polishing it stayed low, so the coating was gone and needed a recoat.

Sessile drop contact angle measurement: DI Water on Teflon surface, left contact angle 108.4°, right 107°

Example ceramic coating maintenance log

Panel state Contact angle (°) Sliding angle (°) Versus gate Meaning Result
Uncoated clearcoat 78.0 No slide by 60 Baseline Reference Reference
Fresh coating, cured 108.5 14 Inside Coating working Pass
After 20 hand washes 104.0 18 Inside Normal wear Pass
After road exposure, unwashed 86.0 No slide by 60 Outside Could be dirt or wear Clean and retest
Same panel after decontamination 102.5 19 Inside Contamination, not failure Pass
After machine polishing 79.5 No slide by 60 Outside Coating removed Recoat

Example data, not customer data. Water contact angle and sliding angle on a coated black clearcoat panel at room temperature, fixed drop volumes, measured after rinsing and drying.

Signal order

The order to check signals when a coating seems to fail

Check these in order. Each one rules out a cause before you look at the next.

1

As found reading

Contact angle and sliding angle before any cleaning.

2

After a decontamination wash

Shows whether contamination was hiding the coating.

3

Sliding angle

Shows whether drops roll off or stay pinned.

4

Spot to spot spread

Shows worn or missed areas against the overall coating.

5

Wear history

Washes, products, polishing and exposure since the last reading.

FAQ

Common questions about hydrophobic and ceramic coating performance

Questions formulators, installers and quality teams ask about measuring hydrophobic performance.

How can you tell if a ceramic coating failed?

Measure water contact angle and sliding angle as found, then again after a proper decontamination wash. If the readings recover, the issue was contamination, not the coating. If they stay close to the uncoated surface, the coating has degraded or been removed and needs a recoat.

Does a high contact angle mean the coating repels water well?

Not always. Feng and colleagues described the petal effect, where drops sit at a high contact angle yet cannot roll off even upside down (Langmuir, 2008). Measure sliding angle as well, because roll off is what keeps a surface clean.

What reduces the lifespan of a hydrophobic coating?

UV and weathering, abrasion from washing and polishing, harsh alkaline or acidic cleaners, and any etching contaminant such as bird droppings. In one study plain water immersion took a silane coating from about 105° to about 90° over 800 hours. Test your own coating against the wear it will see.

What does proper care look like when maintaining ceramic coatings?

To keep your ceramic coating working and maintain ceramic coating performance, proper maintenance means a regular hand wash with a pH neutral car shampoo and a clean microfiber mitt, rinse thoroughly, remove bird droppings and tree sap quickly, and decontaminate every few months. Measuring before and after shows whether a maintenance product helps or harms the coating.

Can a ceramic spray restore the hydrophobic properties?

A ceramic spray topper adds an additional hydrophobic layer and can restore the hydrophobic effect on the surface, but it may mask a worn base coating. Only a recoat can restore the coating once it has worn away. Measure after a decontamination wash and before any topper to see the state of the coating itself.

Which standards apply?

ISO 19403-2 covers surface free energy from contact angles, ISO 19403-6 dynamic contact angle, and ISO 19403-7 roll off on a tilt stage, where the Dropometer is partially compliant up to 60°. Weathering is usually run to ASTM D7869 or SAE J2527.

Which instrument do we need?

Contact angle with water and a second liquid, plus a tilt stage for sliding angle. Our guide to the best contact angle goniometer for industrial QA compares options, and our windshield rain repellent page covers glass coatings.

Business impact

What changes when you measure hydrophobic performance

Typical changes in how teams work. Benchmarks are given only where a published source exists.

Before and with measured hydrophobic performance

Metric Before Dropometer With Dropometer Indicative Benchmark
Failure claims Photos of water beading Readings before and after a clean No published benchmark; track on your own claims
Durability ranking Field trials and opinion Readings after each weathering or wash step 147° to 121° after 120 h weathering for one coating (Pérez-Gandarillas et al., 2023)
Substrate effect Assumed the same everywhere Measured on each substrate Same coating under 50° on glass, above 100° on polycarbonate (Lu et al., 2024)
Batch or install release Visual bead check Contact angle and sliding angle gates No published benchmark; track on your own batches

See the check on your own coating

Send a coated panel that works and one that does not. We will show the difference on a call.

Book a 15 minute demo

Estimate the cost of coating rework

Enter your own numbers. The result is an estimate, not a Droplet Lab claim.

Hydrophobic coating rework estimate

Estimate avoided recoat and rework cost from hydrophobic coating failures.

Each Dropometer unit is $5,000; the default models 1 unit.
Your own average cost to clean, recoat or rework one part, panel or job.
Use your own failure analysis; start low if unsure.
Scrap cost per event from coating failures only, from your own records.

Result

~0
Monthly savings
~0
Payback period
~0
First year net benefit

Monthly savings = preventable rework cost + preventable scrap cost + other monthly savings.

Limits

What contact angle cannot tell you about a coating

Honest limits, so you know when to reach for another test.

A dirty coating reads like a failed one; clean before you judge.
A topper spray can hide a worn base coating.
Sliding angle changes with drop volume; never compare different volumes.
The tilt stage reads up to 60°; drops that do not move are recorded as 60° or more.
Results on one substrate do not transfer to another.
It does not measure gloss, hardness or scratch resistance.

Contact angle and sliding angle measure water and oil repellency. Gloss, hardness, scratch resistance, chemical resistance and long term field life still need their own tests.

Book a 15 minute demo Request a quote
Related

Standards, evidence and related hydrophobic coating workflows

These pages cover the standards, the customer evidence and the other water repellency problems behind this check.

Standard

ISO 19403-2

Surface free energy from contact angle measurements.

View standard

Standard

ISO 19403-7

Roll off angle on a tilt stage for coated surfaces.

View standard

Case study

Aerospace and defense coatings

Oleophobic coating checks with more than one liquid.

Read case study

Case study

University of Calgary

Fibre mats ranked from 130° to 143°.

Read case study

Published paper

Quaking aspen leaves: our analysis

Superhydrophobic leaf surfaces measured with the Dropometer.

Read our analysis

Instrument

Dropometer

Contact angle and sliding angle with the tilt stage.

View product

Related use case

Hydrophobicity and self cleaning

All hydrophobic and anti soiling use cases in one place.

View Page

Related use case

Self cleaning and anti soiling

Validation of self cleaning coatings, including solar panels.

View Page

Related use case

Ski wax glide testing

Hydrophobicity checks on ski glide waxes.

View Page

How this page was created

Editorial and technical transparency notes for this page.

Transparency Details 4 checklist items
01

Drafting assistance

Drafted with Claude Opus 5.5 (Anthropic) using web search for sources, then edited by the Droplet Lab team.

02

Technical review

Reviewed and edited for technical accuracy by the Droplet Lab Team.

03

Verification steps

Standard identifiers, units, thresholds and key procedural claims are checked against cited sources before publication.

04

Updates

Reviewed every 12 months or when the underlying method changes.

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
Sources

References

1.
Pérez-Gandarillas, L., Aragón, D., Manteca, C., Gonzalez-Barriuso, M., Soriano, L., Casas, A., Yedra, A. Highly hydrophobic organic coatings based on organopolysilazanes and silica nanoparticles: evaluation of environmental degradation. Coatings 13(3):537, 2023. https://doi.org/10.3390/coatings13030537
2.
Lu, S., Zhao, Y., Hellerman, E. A. P. UV durable self cleaning coatings for autonomous driving. Scientific Reports 14:8066, 2024. https://www.nature.com/articles/s41598-024-58549-y
3.
Zhizhchenko, A. Y. et al. Stability of octadecyltrimethoxysilane based coatings on aluminum alloy surface. Materials 15(5):1804, 2022. https://doi.org/10.3390/ma15051804
4.
Feng, L., Zhang, Y., Xi, J., Zhu, Y., Wang, N., Xia, F., Jiang, L. Petal effect: a superhydrophobic state with high adhesive force. Langmuir 24(8):4114 to 4119, 2008. https://doi.org/10.1021/la703821h
5.
Ramezanzadeh, B., Mohseni, M., Yari, H. The role of basecoat pigmentation on the biological resistance of an automotive clearcoat. Journal of Coatings Technology and Research 7(6):677 to 689, 2010. https://doi.org/10.1007/s11998-010-9254-5
6.
Superhydrophobicity mechanism of refoliated quaking aspen leaves after complete defoliation by LDD moth caterpillars. Customer publication that used the Dropometer; the link goes to our analysis of the paper. https://dropletlab.com/validation/citations/analysis/superhydrophobicity-mechanism-of-refoliated-quaking-aspen-leaves-after-complete-defoliation-by-ldd-gypsy-spongy-moth-caterpillars/
7.
ISO 19403-2. Paints and varnishes. Wettability. Part 2: Determination of the surface free energy of solid surfaces by measuring the contact angle. https://dropletlab.com/industry-standards/iso-19403-2/
8.
Chen, X. et al. Contact angle measurement with a smartphone. Review of Scientific Instruments 89(3):035117, 2018. https://pubs.aip.org/aip/rsi/article-abstract/89/3/035117/368179/Contact-angle-measurement-with-a-smartphone
9.
Droplet Lab validation papers
10.
Customer publications that cite the Dropometer
11.
ISO 19403-2 explained
12.
Aerospace and defense case study
13.
GIST membrane lab case study