Contents
Partially compliant

IEC TR 62039: selection guidelines for polymeric materials for outdoor use under HV stress

IEC TR 62039 guides the choice of polymeric materials for outdoor high voltage insulation, and its hydrophobicity transfer test is judged by static water contact angle. The Dropometer reads that angle with ±0.35° accuracy (product specification). Tracking, erosion, arc, electrical and weathering tests in the report need their own test equipment.

What brings you here?

Who this is for
Makers of insulators, surge arresters and cable terminations, where the polymeric housing is an integral part of the design, plus silicone compound suppliers and utilities that select outdoor insulation materials.
Compliance tier
Partially compliant: the Dropometer reads the static water contact angle in the hydrophobicity transfer test, not the electrical, mechanical or weathering tests.
Measurement
Sessile drop water contact angle on polluted specimens, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs on a lab bench next to your storage chamber.
Last updated
October 20, 2026
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Free one page checklist for the IEC TR 62039 hydrophobicity transfer test: what to prepare, the settings to lock, how many readings to take and what to record. Made for insulation material labs.

Talk to an expert

Book a 15 minute demo on your housing material

Tell us your compound, your insulator type and your current hydrophobicity check. We will show the measurement live and tell you plainly which parts of IEC TR 62039 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 IEC TR 62039
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

Standard

IEC TR 62039:2021, Selection guidelines for polymeric materials for outdoor use under HV stress, edition 2.0, from IEC TC 112. It replaces the 2007 first edition and adds hydrophobicity definitions, a hydrophobicity transfer test and a stress corrosion test.

Compliance tier

Partially compliant. The Dropometer reads the static water contact angle used to judge hydrophobicity transfer. You make and store the pollution layer. Tracking and erosion, arc resistance, electrical strength, water diffusion, weathering and flammability need their own test sets.

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 paper or case study on insulation materials yet. A published student study used the Dropometer to measure water contact angle as a hydrophobicity check on ski glide waxes. Read our analysis.

What it does not tell you

A contact angle on a lab specimen does not measure leakage current, flashover voltage or tracking. IEC also notes that meeting the minimum requirements is a necessary condition but does not guarantee satisfactory performance when used outdoors.

Executive summary

What this report covers, who uses it and how the Dropometer fits

IEC TR 62039 helps you choose polymeric materials for outdoor insulation under high voltage stress, and its hydrophobicity transfer test is judged by the water contact angle. Insulator, surge arrester and cable accessory makers, compound suppliers and utilities use it to screen housing materials such as silicone rubber for the environmental conditions they will face. The Dropometer is partially compliant: it reads the static water contact angle for the hydrophobicity part with ±0.35° accuracy, but it does not run the report's tracking, erosion, arc, electrical, mechanical, weathering or flammability tests.

The 2021 second edition presents the important material properties of polymeric insulation, the test method for each and minimum requirements where they exist. It is applicable to outdoor high voltage electrical applications above 1,000 V AC or 1,500 V DC (source: IEC webstore listing). This edition added hydrophobicity definitions and a hydrophobicity transfer test. In that test, a thin layer of silica or kieselguhr is put on the material, stored for 96 h, then judged by the static contact angle of water drops on the layer.

The two IEC documents work together. IEC TS 62073 tells you how to measure hydrophobicity: contact angle (Method A), surface tension (Method B) and the spray method (Method C) with its HC1 to HC7 classes. IEC TR 62039 tells you which properties a material should have, takes its hydrophobicity terms from IEC TS 62073, and adds the transfer test.

The Dropometer contact angle and surface energy kit reads static, advancing and receding water contact angles on housing samples in the lab. For the full insulator workflow, see high voltage insulator hydrophobicity. For background, read the utilities guide and the contact angle measurement guide. A drop on a porous pollution layer gives an apparent angle, which the Cassie Baxter model helps explain.

Further reading: reproducible contact angle measurement, experiment 5: Wenzel vs Cassie Baxter, roughness and wetting, client collected wetting measurements dataset, choosing a contact angle goniometer for industrial QA, a membrane research lab case study on liquid repellent surfaces and a study of water contact angle on low fluorinated ski glide waxes.

How the Dropometer fits the selection of polymeric materials for outdoor use

The IEC TR 62039 hydrophobicity transfer test, step by step, in our own words

From polluted specimen to a recorded contact angle

These steps outline the hydrophobicity transfer test and show where the Dropometer fits. They do not replace the report. Buy the current edition and follow its specimen, pollution layer, storage and reading rules.

±0.35°

Contact angle accuracy

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

10° to 175°

Contact angle range

Covers hydrophobic silicone surfaces. A drop that soaks into the layer reads below the range.

About 2 min

Setup

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

1

Prepare the specimens

Make flat specimens of the housing material in the size the standard specifies. Do not polish or touch the test surface. Record the compound, batch, cure and any ageing.

2

Apply the pollution layer

Apply the silica or kieselguhr layer as the standard specifies. Keep the layer thickness and loading the same on every specimen, because both change how fast hydrophobicity moves through it.

3

Store the specimens

Store the polluted specimens for the time and in the climate the standard specifies, 96 h in the published summary. The Dropometer has no temperature or humidity control, so storage happens in your own desiccator or container.

4

Set up the Dropometer

Level the base plate, mount the phone and LED, and fill the syringe with deionised water. Move the specimen onto the stage without disturbing the layer. Custom holders are available on request.

5

Place the drops and read the static angle

Place the drop volume the standard specifies gently on the layer. Keep the needle clear of the surface. Read the angle at a fixed time after placing. Automatic edge and baseline detection gives the same reading from the same image. Take five readings on fresh spots.

6

Record and compare

Record the mean and lowest angle, the layer method, storage time and room conditions. Compare with the limits in your edition of the report. See reproducible contact angle measurement for good bench practice.

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 insulation materials yet. A published student study used the Dropometer to measure water contact angle as a hydrophobicity check on ski glide waxes.

Read our analysis

Set your limits from the report and your own materials

IEC TR 62039 · hydrophobicity transfer · insulation materials

A published summary of the transfer test gives these acceptance criteria for the static water contact angle on the polluted surface: a mean of 90° or higher and a lowest value of 80° or higher, from five readings (source: INMR technical article by Prof. Stefan Kornhuber). Confirm the values, the drop volume and the reading time in your purchased edition of IEC TR 62039 before you use them.

The same summary describes two ways to make the layer: silica powder in a water and isopropanol slurry, spread through a foil window, or kieselguhr with salt solution. Both are stored for 96 h before the reading (same source).

IEC states that meeting the report's minimum requirements is necessary but does not guarantee good service performance (source: IEC TR 62039:2021 listing). So compare new compounds with a reference material that has a known field record, and repeat the test when you change filler, curing or supplier.

Example output

Example data for illustration only. These are not measured results. Your own materials, pollution layer and the limits in your edition of the report decide the numbers.

Example: hydrophobicity transfer test on four housing materials, silica layer, after 96 h

Material Readings (n) Mean angle (°) Lowest angle (°) Std dev (°) Decision
Silicone rubber, HTV grade A5102.999.52.4Meets both criteria
Silicone rubber, LSR grade B590.786.23.6Meets, close to the limit: repeat on a second specimen
Silicone rubber, grade C555.541.611.3Does not meet: little transfer
EPDM5Below 10Below 10n/aDoes not meet: drops soaked into the layer

How to read this table

Each row is five static water contact angle readings on one polluted specimen. The decision column uses the published summary criteria: mean 90° or higher and lowest reading 80° or higher.

Example output chart

The same example data as the table, plotted against the published summary criteria. The EPDM specimen is left out because the drops soaked into the layer.

Bar chart of example mean static water contact angles on three silicone rubber grades after a hydrophobicity transfer test, with the 90 degree mean and 80 degree lowest reading criteria marked

Example data, not measured results.

Business impact

What changes when the transfer test is a measured angle in your own lab

Metric Before Dropometer With Dropometer Results
Where the reading runs Shared goniometer in a central lab On a bench next to your storage chamber, on battery for up to 8 h Dropometer product specification
Result format Drop behaviour on the layer judged by eye An angle per reading, 0.01° display, ±0.35° accuracy Dropometer product specification
Record Operator note Drop image and angle saved per reading No published benchmark
Tracking, arc and electrical tests Dedicated test sets to IEC 60587, IEC 61621 and others Still need those test sets IEC TR 62039 normative references

See the measurement on your own material

Bring two polluted specimens: a reference material with a good field record and a new compound. We will read both live.

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ROI estimate

Estimate the cost of the insulation material 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

Lock these before you compare materials or labs

Parameter Recommended Setting Technical Rationale
Test liquid Deionised water The transfer test reads the water contact angle on the polluted surface.
Drop type Sessile drop, static angle The published criteria use the static angle, not the receding angle.
Drop volume As the standard specifies, fixed for every drop A changing volume adds spread that is not about transfer. The automatic dropper doses down to 0.05 µL.
Pollution layer Silica or kieselguhr method, as the standard specifies The two layer methods are different. Report which one you used.
Storage 96 h at the climate the standard specifies Transfer takes time. Read every specimen after the same storage time.
Readings Five per specimen, fresh spot each time The published criteria use the mean and the lowest of five readings.
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.
Environment Record room temperature and humidity at the reading The Dropometer runs at 10 to 45 °C and has no temperature or humidity control.

Is IEC TR 62039 the right publication?

Pick the method by the question you need answered

Start: What do you need to know about your insulation material?

Hydrophobicity transfer through a pollution layer

Signals:

You are selecting a housing material and need to know whether its hydrophobicity moves through a dirt layer.

Rule-out:

Use the IEC TR 62039 transfer test, this page. The Dropometer reads the static contact angle; you make and store the layer.

Contact angle on new or aged samples

Signals:

You need static, advancing or receding angles on housing samples, before and after ageing.

Rule-out:

Use Method A of IEC TS 62073. The Dropometer is fully compliant with that method.

Hydrophobicity class of installed insulators

Signals:

You inspect insulators in service and need an HC1 to HC7 class.

Rule-out:

Use the spray method, Method C of IEC TS 62073, judged by eye. The Dropometer does not run it.

Tracking, erosion, arc or electrical strength

Signals:

You need the other material properties IEC TR 62039 lists.

Rule-out:

Use the report's test methods, including IEC 60587 for tracking and erosion and IEC 61621 for arc resistance, on their own test sets. Contact angle complements them.

Decision tree at a glance

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

Decision tree for choosing between the IEC TR 62039 transfer test, IEC TS 62073 Method A contact angle, the IEC TS 62073 spray method and the electrical material tests

Is IEC TR 62039 the right document?

Interpreting results for outdoor use under HV stress

What the angle on a polluted surface tells you, and what it does not

High angle on the layer means transfer: Low molecular weight silicone moves into the dirt layer and makes it repel water, so the drop beads up.
A soaked in drop means no transfer: If the layer stays wettable, water spreads into it and the angle falls below the Dropometer's 10° range.
The angle on a layer is apparent: The porous powder layer is rough, so the reading reflects texture as well as chemistry. Compare each type of material on the same layer method.
Transfer is not retention: The transfer test does not show how a material keeps or recovers hydrophobicity under discharges. Track that with repeat angles after ageing.
Expert perspective

Why the contact angle on a polluted surface tracks hydrophobicity transfer

Pick the measurement to match the question: the same surface can read one way as a sessile drop and another on a tilted plate, and both can be the right answer.

Dr. Alidad Amirfazli

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

Common pitfalls and limits

Honest limits of the method and of the Dropometer

Uneven layer thickness changes how fast hydrophobicity moves through it. Use the same window or loading on every specimen.
Drops that soak into the layer read below the 10° range. Record them as no reading, not as a number.
The Dropometer has no temperature or humidity control. Store specimens in your own chamber and record room conditions at the reading.
The camera runs at 10 frames per second. That suits a reading at a fixed time, not millisecond spreading into the layer.
Lab specimens are not energized insulators. The angle does not measure leakage current, tracking or flashover.
FAQ

Frequently asked questions

What is IEC TR 62039?

It is an IEC Technical Report that guides the choice of polymeric materials used in outdoor insulation, for high voltage electrical applications with a system voltage greater than 1,000 V AC or 1,500 V DC. It lists the important material properties of polymeric materials, the test method for each and minimum requirements where they exist. The current publication is edition 2.0, from 2021.

How is IEC TR 62039 related to IEC TS 62073?

IEC TS 62073 tells you how to measure hydrophobicity on insulator surfaces, by contact angle, surface tension or the spray method. IEC TR 62039 tells you which properties a material should have. It takes its hydrophobicity terms and HC classes from IEC TS 62073 and adds a transfer test. See IEC TS 62073.

Can the Dropometer run the IEC TR 62039 tests?

In part. The Dropometer reads the static water contact angle used in the hydrophobicity transfer test, with ±0.35° accuracy. You make and store the pollution layer yourself. Tracking and erosion, arc resistance, electrical strength, weathering and flammability need their own test sets.

What contact angle does the IEC TR 62039 transfer test require?

A published summary gives a mean static water contact angle of 90° or higher and a lowest value of 80° or higher, from five readings (source: INMR technical article). Confirm the values in your purchased edition before you write them into a specification.

Does the report cover hydrophobicity recovery after ageing?

The report discusses retention and recovery, but its introduction notes that agreed test methods and minimum requirements were still under development. Many labs track recovery by reading the contact angle at set times after ageing, with Method A of IEC TS 62073.

Should I use the static or the receding contact angle on insulator materials?

Use the angle your test names. The transfer test criteria use the static angle. IEC TS 62073 also covers advancing and receding angles, which the Dropometer measures by adding or withdrawing liquid through the needle.

Legal note

This page summarises IEC TR 62039 in our own words and does not reproduce the report. Buy the current edition from IEC before you write a procedure. The Dropometer is partially compliant with this report. 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

IEC TR 62039:2021 listing (IEC webstore); IEC TR 62039:2021 preview: scope, contents, foreword (VDE Verlag); IEC TS 62073:2016 preview: scope and contents (VDE Verlag); INMR: Evaluating hydrophobicity transfer and retention (Prof. Stefan Kornhuber), 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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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.

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References

1. IEC TR 62039:2021. webstore.iec.ch/en/publication/59945
2. IEC TR 62039:2021 preview: scope, contents, foreword (VDE Verlag). assets.vde-verlag.de/iec-normen/preview-pdf/info_iectr62039%7Bed2.0%7D
3. IEC TS 62073:2016 preview: scope and contents (VDE Verlag). assets.vde-verlag.de/iec-normen/preview-pdf/info_iec62073%7Bed2.0%7Den
4. INMR: Evaluating hydrophobicity transfer and retention (Prof. Stefan Kornhuber). inmr.com/
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/