Contents
Partially compliant

ISO 14778 standard: optical measurement method for the water contact angle on paper and board (ISO/TS 14778:2021)

Check how well paper and board resist water by reading the water contact angle over time, the measurement ISO/TS 14778 describes. The Dropometer reads the angle at fixed times from about 0.1 s, with ±0.35° accuracy (Dropometer product specification), on a drop shape method validated in two peer reviewed papers. It is too slow for the method's first reading at 20 to 40 ms.

What brings you here?

Who this is for
Paper mills, board and packaging converters, and labs that check sizing and water resistance of paper and board.
Compliance tier
Partially compliant: the Dropometer reads the water contact angle at fixed times from about 0.1 s, but not the 20 to 40 ms first reading.
Measurement
Sessile drop water contact angle over time, 10° to 175° range, ±0.35° accuracy, 10 frames per second (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs at the machine or in the lab.
Last updated
October 20, 2026
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Free one page checklist for ISO/TS 14778: what to prepare, the reading times to lock, what the Dropometer can and cannot capture, and what to record. Made for paper and board QC benches.

Talk to an expert

Book a 15 minute demo on your paper or board

Tell us your grade, sizing and current water test. We will show the measurement live and tell you plainly which ISO/TS 14778 readings the Dropometer can take and which need a high speed tester.

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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.
Read More
Verified against ISO 14778
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: the ISO 14778 standard and the Dropometer

Standard

ISO/TS 14778:2021, Paper and board: Measurement of water contact angle by optical methods, a Technical Specification from ISO/TC 6/SC 2. ISO confirmed it at the 2024 systematic review. See the ISO listing.

Compliance tier

Partially compliant. The method calls for image capture at 50 frames per second or faster and a first reading within 20 to 40 ms of contact. The Dropometer captures at 10 frames per second, so it covers fixed time readings from about 0.1 s only.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°, camera 10 frames per second, 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

A labels and office products manufacturer uses the Dropometer to see how inks and adhesives wet film, paper, board and plastic. Read the case study.

What it does not tell you

Contact angle does not give grams of water absorbed. For that, use the Cobb test to ISO 535 or TAPPI T 441.

Executive summary

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

ISO 14778, published as ISO/TS 14778:2021, measures the water contact angle on paper and board with automated optical equipment: a higher, steadier angle means the sheet resists water better. Paper mills, board converters and packaging labs use it in quality control to check sizing and how fast water wets and soaks into the sheet. The Dropometer is partially compliant: it reads the angle at fixed times from about 0.1 s, but it cannot take the method's first reading at 20 to 40 ms.

The method places a water drop on a flat test piece and measures the droplet shape in contact with the solid as it spreads and soaks in. ISO calls for image capture at 50 frames per second or faster, so the first angle is read before an absorbent sheet takes up the drop (source: ISO/TS 14778:2021 listing). It suits most kinds of paper or board, but not structured materials.

The Dropometer contact angle and surface energy kit captures at 10 frames per second. That suits readings at about 0.1 s, 1 s, 10 s and later, which show how the angle falls as the sheet absorbs water. To keep those readings comparable between operators and sites, follow our steps for reproducible contact angle measurement and the contact angle measurement guide. If you need the full high speed method, our buying guide for ISO and GLP regulated high throughput QC compares the options.

Further reading: the packaging and containers guide, wicking control for paper microfluidic and lateral flow tests, wettability in our glossary, and water contact angle reference values for common surfaces.

How the Dropometer fits the optical measurement method

The ISO/TS 14778 measurement, step by step, in our own words

From paper sample to angles over time

These steps outline the procedure and show where the Dropometer fits. They do not replace the standard. Buy the current edition and follow its drop volume, timing, conditioning and specimen rules.

±0.35°

Contact angle accuracy

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

10 fps

Camera speed

Fine for readings from about 0.1 s on. Too slow for the 20 to 40 ms first reading.

About 2 min

Setup

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

1

Sample and condition the sheet

Cut flat test pieces and mark the side you test. Handle them by the edges, because skin oils change the angle. Condition and test them in the atmosphere the standard specifies.

2

Set up the Dropometer

Place the base plate on a level bench, mount the phone and LED, and fill the syringe with water of the grade the standard specifies. Lay the test piece flat on the sessile stage, test side up.

3

Place the drop the same way every time

Dispense the drop volume the standard specifies. The automatic dropper add-on helps keep the volume the same for every drop. Do not touch the sheet with the needle.

4

Read the angle at fixed times

Capture the drop as it spreads and soaks in, and read the angle at your agreed times, for example about 0.1 s, 1 s and 10 s. At 10 frames per second the first frame can land at any point in the first 0.1 s, so the Dropometer cannot supply the 20 to 40 ms reading.

5

Repeat across the sheet

Place several drops on fresh, unwetted areas of each test piece. Sizing and formation vary across the sheet, so one drop is not enough.

6

Record and compare

Record the mean and spread at each time, the side tested, grade and room conditions. Compare with limits from your own study. Check your numbers against our water contact angle reference values for a sanity check.

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 on ISO/TS 14778 yet. A labels manufacturer uses the Dropometer in two labs to check how inks, adhesives and coatings wet paper, board and film.

Read the case study

Set your limits from your own paper and board

ISO/TS 14778 · sizing · paper and board QC

The public ISO/TS 14778 summary gives no pass or fail angle for paper or board (source: ISO/TS 14778:2021 listing). Limits are set from your own correlation or capability study.

Measure grades that printed, glued and held up to water well, and grades that failed. Read each one at the same fixed times, for example about 0.1 s, 1 s and 10 s. Then set an accept limit on the angle at one time, or on how far it falls between two times.

If your limit depends on the angle in the first 40 ms, the Dropometer cannot supply it. Use a tester that captures at 50 frames per second or faster for that reading. Repeat the study when you change furnish, sizing agent, coating or calender settings.

Example output

Example data for illustration only. These are not measured results. Your own grades, sizing and limits decide the numbers.

Example: water contact angle over time on four paper and board grades

Grade Drops (n) About 0.1 s (°) 1 s (°) 10 s (°) Reading
Coated board, print side1098.497.194.6Stable angle: strong water resistance
Hard sized liner1092.386.074.5Slow fall: compare with your limit
Lightly sized paper1078.655.222.4Fast fall: review sizing
Unsized tissue10Below 10°Below 10°Below 10°Soaked in before 0.1 s: needs a high speed tester

How to read this table

Each value is the mean of ten drops on one grade. Readings at about 0.1 s, 1 s and 10 s are later fixed times the Dropometer can capture. No published limits apply: the reading column shows how an example lab might act after its own correlation study.

Example output chart

The same example data as the table, plotted on a log time axis. The unsized tissue is left out because its drop soaked in before the first reading.

Line chart of example water contact angles at about 0.1, 1 and 10 seconds on coated board, hard sized liner and lightly sized paper, showing the angle falling fastest on the lightly sized paper

Example data, not measured results.

Business impact

What changes when the water check is a measured angle over time

Metric Before Dropometer With Dropometer Results
How the check is made Water drop or feather test, judged by eye Water contact angle read from the drop image at fixed times No published benchmark
Result format Pass or fail, or soak time by stopwatch An angle per drop per time, 0.01° display, ±0.35° accuracy Dropometer product specification
Earliest reading High speed tester: within 20 to 40 ms of contact Dropometer: about 0.1 s, at 10 frames per second ISO/TS 14778:2021 listing; Dropometer product specification
Where it runs Shared lab tester At the machine or in the lab, on battery for up to 8 h Dropometer product specification

See the measurement on your own sheet

Bring two samples: one grade that held up to water and one that did not. We will measure both live and show the angle at each reading time.

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ROI estimate

Estimate the cost of the sizing 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 water contact angle on paper and board

Lock these before you compare results between shifts or sites

Parameter Recommended Setting Technical Rationale
Test liquid Water of the grade the standard specifies This is a water contact angle method. Other liquids belong to other methods.
Drop type Sessile drop, angle read over time Paper and board absorb water, so the angle falls after contact.
Drop volume As the standard specifies, fixed for every drop A changing volume changes how fast the drop soaks in.
First reading Within 20 to 40 ms, at 50 frames per second or faster ISO/TS 14778 scope. The Dropometer captures at 10 frames per second and cannot take this reading.
Later readings Fixed times you agree, for example about 0.1 s, 1 s and 10 s The Dropometer covers these. Keep the same times for every drop and grade.
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.
Replicates Several drops on fresh areas of each test piece Sizing and formation vary across the sheet.
Environment Condition and test as the standard specifies; record temperature and humidity Paper picks up moisture from the air. The Dropometer runs at 10 to 45 °C and has no humidity control.

Is ISO/TS 14778 the right test?

Pick the method by the question you need answered

Start: What do you need to know about water on your paper or board?

The angle in the first 40 ms

Signals:

Your sheet absorbs water fast, or your customer names ISO/TS 14778 and its first reading.

Rule-out:

Use ISO/TS 14778 on a tester that captures at 50 frames per second or faster. The Dropometer cannot take this reading.

Angles at fixed times from 0.1 s

Signals:

You want to trend sizing by how the angle falls at about 0.1 s, 1 s and 10 s.

Rule-out:

The Dropometer takes these readings: partially compliant with ISO/TS 14778. For automated checkpoints at the same times, see TAPPI T 558.

Classic readings at 5 s and 60 s

Signals:

Your specification names the older TAPPI method for writing and ruling quality.

Rule-out:

Use TAPPI T 458 / ASTM D724. The Dropometer covers those reading times.

Grams of water absorbed

Signals:

You need water absorptiveness in g/m² over a set time, not an angle.

Rule-out:

Use the Cobb test to ISO 535 or TAPPI T 441. Contact angle complements 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 the ISO/TS 14778 first reading on a high speed tester, fixed time contact angle readings, TAPPI T 458 and the Cobb test

Is ISO/TS 14778 the right test?

Interpreting the contact angle measurement over time

What the angle over time tells you, and what it does not

Higher early angle, better sizing: A sized or coated sheet holds the drop up longer, so the early angle is higher.
The fall over time matters: This dynamic contact angle, and how fast it drops, shows how fast water spreads and soaks in. Compare grades at the same times.
One time point can mislead: Two grades can match at 1 s and differ widely at 10 s. Read at least two times.
Angle is not absorbed water: A falling angle shows absorption is happening. It does not give grams of water taken up. That is the Cobb test.
Expert perspective

Why the reading time changes the answer on paper

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

Common pitfalls and limits

Honest limits of the method and of the Dropometer

The Dropometer camera runs at 10 frames per second. It cannot take the 20 to 40 ms first reading ISO/TS 14778 calls for.
At 10 frames per second the first frame can land at any point in the first 0.1 s after contact, so treat 0.1 s as approximate.
Very absorbent sheets can take up the drop before 0.1 s or drop below the 10° range limit. Use a high speed tester.
The Dropometer has no temperature or humidity control. Test in a conditioned room and record the conditions.
The method does not cover structured materials. Embossed, creped or textured sheets give an apparent angle.
FAQ

Frequently asked questions

Is ISO 14778 a full International Standard?

No. It is ISO/TS 14778:2021, a Technical Specification and the first edition. ISO reviewed and confirmed it in 2024, so it is still current. Quote the full designation, ISO/TS 14778:2021, in your test report.

Can the Dropometer run ISO 14778?

Partly. ISO/TS 14778 calls for capture at 50 frames per second or faster and a first reading within 20 to 40 ms of contact. The Dropometer captures at 10 frames per second. It reads the angle at fixed times from about 0.1 s with ±0.35° accuracy, but not that first reading.

Why does ISO 14778 need such a fast camera?

Absorbent paper can take up a water drop within a fraction of a second. A fast camera reads the angle before the drop soaks in. On sized or coated grades the angle falls slowly, so later readings still tell you a lot.

How is ISO 14778 different from TAPPI T 458 and TAPPI T 558?

TAPPI T 458 is an older classical method that reads the angle at 5 s and 60 s (TAPPI T 458 review draft, 2024). TAPPI T 558 uses an automated tester with checkpoints at 0.1 s, 1 s and 10 s (TAPPI T 558 review draft, 2025). ISO/TS 14778 also uses automated capture and adds the 20 to 40 ms first reading. See TAPPI T 458 and TAPPI T 558.

What water contact angle shows good sizing?

The public summary of ISO/TS 14778 gives no pass or fail angle. Set limits from your own correlation study: measure grades that held up to water and grades that failed, at the same reading times.

Does contact angle replace the Cobb test?

No. The Cobb test gives grams of water absorbed per square metre in a set time. Contact angle shows how water wets the surface and how fast that changes. Many mills run both. See ISO 535 and TAPPI T 441.

Legal note

This page summarises ISO/TS 14778:2021 in our own words and does not reproduce the standard. Buy the current edition from ISO or your national standards body before you write a procedure. 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

ISO/TS 14778:2021 listing; BSI PD ISO/TS 14778:2021 listing; iTeh ISO/TS 14778:2021 preview (scope and contents); TAPPI T 558 review draft, 2025, 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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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.

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References

1. ISO/TS 14778:2021. iso.org/standard/66468.html
2. BSI PD ISO/TS 14778:2021 listing. knowledge.bsigroup.com/products/paper-and-board-measurement-of-water-c
3. iTeh ISO/TS 14778:2021 preview (scope and contents). iteh.es/catalog/standards/iso/5ea909ca-3f0f-4036-b210-5f017c55ba12/iso
4. TAPPI T 558 review draft, 2025. tappi.org/contentassets/58af997fbe9b4f40a7545ee183554082/2025/t558-b-2
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/