Contents
Fully compliant

TAPPI T 458 / ASTM D724: surface wettability of paper by water contact angle

Check how well paper resists wetting by reading the water contact angle at 5 s and 60 s, the measurement TAPPI T 458 describes. The first reading points to ruling quality and the change points to writing quality. The Dropometer runs this measurement at the mill or in the lab, with ±0.35° accuracy (Dropometer product specification), on a drop shape method validated in two peer reviewed papers.

What brings you here?

Who this is for
Paper mills, converters and printers who check ruling and writing quality, plus labs that build paper based devices.
Compliance tier
Fully compliant: the Dropometer measures the timed sessile drop contact angle this method describes.
Measurement
Sessile drop water contact angle read at 5 s and 60 s, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs at the mill or in the lab.
Last updated
October 20, 2026
Book a 15 minute demo Request a quote

Free one page checklist for TAPPI T 458: what to prepare, the settings to lock, when to read the angle and what to record. Made for paper QC benches.

Talk to an expert

Book a 15 minute demo on your paper

Tell us your paper grade, sizing and current check. We will show the measurement live and tell you plainly where the Dropometer fits your QC plan and where it does not.

Book a 15 minute demo
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
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
Verified against TAPPI T 458 cm-24 / ASTM D724
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

TAPPI T 458 cm-24, Surface wettability of paper (angle of contact method), a classical method from TAPPI, the Technical Association of the Pulp and Paper Industry. ASTM D724-99(2003) covered the same method; ASTM withdrew it in 2009 with no replacement (ASTM listing).

Compliance tier

Fully compliant. The Dropometer measures the sessile drop contact angle at fixed times. The method reads at 5 s and 60 s, well inside what a 10 frames per second camera captures.

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

A paper microfluidics study in Sensors and Actuators B (2023) used the Dropometer for water contact angle on the device's Parafilm barrier, not on the paper itself. Read our analysis.

What it does not tell you

TAPPI limits the method to ruling and writing. It does not measure how much water the sheet absorbs over minutes, or whether a coating or adhesive bonds.

Executive summary

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

TAPPI T 458 measures the water contact angle on paper at two fixed times, 5 s and 60 s, to show how well the sheet resists wetting. The first reading points to ruling quality and the change between readings points to writing quality. The Dropometer is fully compliant with this measurement and reads each drop with ±0.35° accuracy (Dropometer product specification).

ASTM D724 described the same angle of contact method, but ASTM withdrew it in 2009 with no replacement. TAPPI T 458 cm-24 is the current edition to cite. The method places a drop of water, or an ink agreed between buyer and seller, on conditioned paper strips. You report the mean first angle and the rate of change in degrees per second for each side of the sheet. TAPPI limits the method to ruling and writing paper; other uses need real changes to the procedure.

The Dropometer contact angle and surface energy kit records the drop at 10 frames per second, so readings at 5 s and 60 s sit well inside what the camera captures. Start with our contact angle glossary entry and the contact angle measurement guide. To keep timed readings consistent between operators, see reproducible contact angle measurement. For typical values on common materials, see our water contact angle reference values.

Paper based diagnostics rely on the same timed reading. See paper microfluidic and lateral flow wicking control and our university paper microfluidics case study. A paper microfluidics study in Sensors and Actuators B used the Dropometer for water contact angle on the device's Parafilm barrier.

Further reading: the packaging and containers guide, our pick of the best contact angle goniometer for industrial QA, and a blog post on the Leidenfrost effect.

How the Dropometer fits the contact angle method on paper

The TAPPI T 458 measurement, step by step, in our own words

From paper strip to two recorded angles

These steps outline the procedure. They do not replace the standard. Buy the current edition and follow its liquid, drop volume, specimen and conditioning rules.

±0.35°

Contact angle accuracy

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

About 2 min

Setup

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

10 fps

Camera frame rate

Readings at 5 s and 60 s sit well inside what the camera captures.

1

Cut and condition the strips

Cut strips free of creases, spots and watermarks, and mark the top and wire sides. Handle them by the edges, since skin oils change the angle. Condition 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 distilled water or the agreed ink. Lay the strip flat on the sessile stage with the side under test facing up.

3

Place the drop and start recording

Dispense the drop volume the standard specifies onto an unwetted area. Record from the moment the drop touches the paper, so the clock starts at contact. Do not touch the paper with the needle.

4

Read the angle at 5 s and 60 s

Read the angle at 5 s and again at 60 s from the recording. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image.

5

Repeat on both sides

Place several drops on each side of the sheet, each on a fresh area. Sizing and texture often differ between the top and wire sides, so keep their results apart.

6

Calculate and record

Record the mean 5 s angle, the mean 60 s angle and the rate of change in degrees per second for each side. Note the liquid, drop volume and room conditions. For drops that soak in fast, see wettability and wicking use cases.

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 TAPPI T 458 yet. A paper microfluidics study used the Dropometer for water contact angle on a Parafilm barrier, and Concordia's paper sensor lab uses it for contact angle work.

Read the case study

Set limits for your own paper product

TAPPI T 458 · ruling and writing quality · paper QC

TAPPI's 2024 ballot draft of T 458 links water contact angles of 90 to 110° with excellent ruling. Above 110° can break ruled lines, and below 90° suggests feathering (source: TAPPI T 458 ballot draft, 2024). The withdrawn ASTM D724 summary noted that 90 to 100° with its standard ink often suited general water based ink (source: ASTM D724-99(2003) listing).

The same TAPPI draft gives precision data: repeatability of 3 to 4% for angles of 90° or more and reproducibility of 7% between operators. So treat these ranges as a starting point. Measure paper that ruled and wrote well, and paper that feathered, then set your limits from that correlation study.

Repeat the study when you change furnish, sizing level or surface treatment.

Example output

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

Example: two writing paper grades, top and wire side, water read at 5 s and 60 s

Sample and side Drops (n) Angle at 5 s (°) Angle at 60 s (°) Rate of change (°/s) Decision
Grade A, top side598.492.90.10Accept
Grade A, wire side595.188.50.12Accept
Grade B, top side586.271.90.26Hold the lot, check sizing
Grade B, wire side584.068.10.29Hold the lot, check sizing

How to read this table

Each row is the mean of five drops on one side. Rate of change is the 5 s angle minus the 60 s angle, divided by 55 s. The decision column uses example limits of 90° or higher at 5 s and 0.15 °/s or lower, set from a correlation study.

Example output chart

The same example data as the table: the 5 s angle per sample and side, plotted against the TAPPI ruling range and an example accept limit.

Bar chart of example water contact angles at 5 s on the top and wire sides of two writing paper grades, with a 90 degree accept limit and the 110 degree top of the TAPPI ruling range

Example data, not measured results.

Business impact

What changes when the timed reading comes from a recorded drop

Metric Before Dropometer With Dropometer Results
How the angle is read Projected drop traced and read with a protractor Angle read from the drop image by edge and baseline detection No published benchmark
Timing of the readings Stopwatch and a quick manual reading Drop recorded at 10 frames per second, read at 5 s and 60 s TAPPI notes timing variability can push projection results past its reproducibility figure
Result format One reading per drop, rounded by eye An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Where it runs Shared lab goniometer At the mill QC bench, on battery for up to 8 h Dropometer product specification

See the measurement on your own paper

Bring two samples: one that ruled and wrote well and one that feathered. We will measure both live.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of the ruling and writing defects 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.

Test method settings

Lock these before you compare results between shifts or mills

Parameter Recommended Setting Technical Rationale
Test liquid Distilled water, or the ink agreed between parties Name the liquid in every report. Results with different liquids do not compare.
Drop type Sessile drop, static angle read at two times The method reads a resting drop on the paper surface.
Drop volume As the standard specifies, fixed for every drop A changing volume adds spread that is not about the paper.
Reading times 5 s and 60 s after the drop touches the paper The first angle points to ruling quality; the change points to writing quality.
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 As the standard specifies, each drop on an unwetted area Paper varies across the sheet, so one drop is not enough.
Sides tested Top and wire side, reported separately Sizing and texture often differ between the two sides.
Environment Conditioned room as the standard specifies; record it The Dropometer runs at 10 to 45 °C and has no temperature or humidity control.

Is TAPPI T 458 the right test?

Pick the method by the question you need answered

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

Ruling and writing quality

Signals:

You want a measured value for how ink lines will rule and how writing will hold on the sheet.

Rule-out:

Use TAPPI T 458, this page. The Dropometer is fully compliant.

Water absorbed over minutes

Signals:

You need to know how much water sized paper or paperboard takes up, not how a drop sits on it.

Rule-out:

Use a Cobb test such as TAPPI T 441 or ISO 535. Contact angle complements it.

Treated film, not paper

Signals:

Your substrate is a corona treated polymer film that does not absorb water.

Rule-out:

Use ASTM D5946 / ISO 15989. The Dropometer is fully compliant.

Whether a coating or ink bonds

Signals:

You need to know if a cured coating or print stays on, not only whether it wets.

Rule-out:

Use an adhesion test such as ASTM D3359.

Decision tree at a glance

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

Decision tree for choosing between TAPPI T 458 water contact angle, a Cobb absorption test, ASTM D5946 for treated film and an ASTM D3359 adhesion test

Is TAPPI T 458 the right test?

Interpreting contact angle results on paper

What the two angles tell you, and what they do not

Higher first angle, better resistance: Sized paper holds the drop up. A high angle at 5 s means ink lines stay sharp when ruled.
Too high can also hurt: TAPPI's 2024 ballot draft links water angles above 110° to breaks in ruled lines.
Rate of change shows spreading and uptake: A fast fall between 5 s and 60 s shows the dynamic part of wetting: the liquid spreads or soaks in, which affects writing.
The two sides can differ: Top and wire sides often differ in sizing and texture. Report them separately.
Expert perspective

Why the top layer of the sheet decides wetting

Wettability is set by the top five to ten ångström of a surface: what the liquid actually sees. It doesn't matter what lies beneath; that outermost layer is what you are really measuring.

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

Very absorbent paper can take the angle below 10°, the bottom of the Dropometer range. Use an absorption test there.
The camera runs at 10 frames per second. That suits readings at 5 s and 60 s, not millisecond absorption studies.
The Dropometer has no temperature or humidity control. Test in a conditioned room and record its conditions.
Rough or fibrous surfaces give an apparent angle that reflects texture as well as sizing.
TAPPI limits the method to ruling and writing. Other uses, such as adhesives, need real changes to the procedure.
FAQ

Frequently asked questions

Is ASTM D724 still current?

No. ASTM withdrew D724-99(2003) in 2009 with no replacement (ASTM listing). TAPPI T 458 cm-24 covers the same angle of contact method for paper. If a specification still names D724, agree with your customer to test to TAPPI T 458.

What does TAPPI T 458 measure?

It measures the contact angle of a liquid on a paper surface: water, or an agreed ink. TAPPI takes the initial angle of contact as a measure of the resistance of the paper surface to wetting, and so of the ruling quality of the paper. The rate of change in the wettability points to writing quality.

When does TAPPI T 458 read the contact angle?

At 5 s and 60 s after the drop touches the paper. The rate of change is the difference between the two angles divided by the time between them, in degrees per second. Both times sit well inside what a 10 frames per second camera captures.

Can the Dropometer run TAPPI T 458?

Yes. The Dropometer measures the sessile drop contact angle at fixed times, which is what the method reads. Accuracy is ±0.35°. Buy the current edition of the standard, follow its liquid, drop volume and conditioning rules, and validate the method in your own lab.

What water contact angle on paper shows good ruling quality?

TAPPI's 2024 ballot draft of T 458 links water angles of 90 to 110° with excellent ruling. Above 110° can break ruled lines, and below 90° suggests feathering. Use these ranges as a starting point and set your limits from paper that ruled and wrote well.

How is TAPPI T 458 different from the Cobb test?

TAPPI T 458 reads how a drop sits on the surface over one minute. A Cobb test weighs how much water the sheet absorbs over a set time. Many mills run both. See TAPPI T 441 and ISO 535.

Legal note

This page summarises TAPPI T 458 in our own words and does not reproduce it. ASTM withdrew D724 in 2009. Buy the current edition from TAPPI before you write a procedure. 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

TAPPI T 458 cm-24 listing (TAPPI store); TAPPI T 458 cm-24:2024 listing (ANSI Webstore); TAPPI T 458 ballot draft, 2024 (SARG); ASTM D724-99(2003) listing, withdrawn 2009, 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

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

References

1. TAPPI T 458 cm-24 / ASTM D724-99(2003), withdrawn. imisrise.tappi.org/TAPPI/Products/01/T/0104T458.aspx
2. TAPPI T 458 cm-24:2024 listing (ANSI Webstore). webstore.ansi.org/standards/tappi/tappi458cm242024
3. TAPPI T 458 ballot draft, 2024 (SARG). ektron.tappi.org/contentassets/58af997fbe9b4f40a7545ee183554082/t458-d
4. ASTM D724-99(2003) listing, withdrawn 2009. store.astm.org/d0724-99r03.html
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/