Contents
Complements workflow

AATCC TM22 test method for water repellency: the textile spray test, and where contact and sliding angle fit

AATCC TM22 gives a spray rating: a visual score of how much a fabric wets under a standard water spray. The Dropometer does not measure that rating, so it complements the TM22 workflow. With the fabric holder option it measures water contact angle and sliding angle on the fabric. Those numbers rank finishes and track wash durability before you confirm with the spray test.

What brings you here?

Who this is for
Textile mills, DWR finish makers, outdoor and workwear brands, and textile research groups who work with water repellent fabric.
Compliance tier
Complements workflow: the Dropometer does not give a spray rating. It measures contact and sliding angle on the fabric before and after the spray test.
Measurement
Sessile drop water contact angle, 10° to 175° range, ±0.35° accuracy, and sliding angle on a 0 to 60° tilt stage (Dropometer datasheet). Fabric holder option.
Setup
About 2 minutes. Battery powered, 1 kg, runs in the lab or next to the finishing line.
Last updated
October 20, 2026
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TM22 Apparatus
Dropometer Measuring Contact Angle
TM22 Apparatus

Free one page checklist for screening DWR fabric with contact and sliding angle before the AATCC TM22 spray test: what to prepare, the settings to lock and what to record.

Talk to an expert

Book a 15 minute demo on your fabric

Tell us your fabric, finish and the spray ratings you need. We will measure contact and sliding angle live and tell you plainly where the Dropometer fits next to your spray tester and where 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
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 AATCC TM22: Water Repellency Spray Test
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: AATCC TM22 and the Dropometer

Standard

AATCC TM22-2024, Test Method for Water Repellency: Spray Test, from AATCC, the American Association of Textile Chemists and Colorists. Older specifications may still cite earlier editions such as TM22-2014. It applies to any textile fabric, finished or not, and rates the wetted pattern left by a standard spray against a photographic scale. ISO 4920:2012 describes a spray test for resistance to surface wetting.

Compliance tier

Complements workflow. The Dropometer does not measure a spray rating, the quantity TM22 reports. It measures water contact angle and sliding angle on the fabric, which explain why a fabric rates well or badly and let you screen finishes before the spray test.

Instrument performance

Contact angle range 10° to 175°, accuracy ±0.35°, display resolution 0.01°. Sliding angle on a tilt stage from 0 to 60°, manual, with an automatic sliding stage add-on. Fabric holder option. All 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 federal research team in Canada used the Dropometer on water repellent coatings applied to white polyester fabric. Read the case study. University researchers also used a Droplet Lab goniometer to measure water contact angles of 130.1° to 143.2° on electrospun polystyrene fibre mats (Macromolecular Rapid Communications, 2024). Read our analysis of the paper.

What it does not tell you

Neither the spray rating nor drop angles measure water passing through the fabric. ISO states its spray test is not meant to predict rain penetration (source: ISO 4920:2012 abstract). Use a penetration test for that.

Executive summary

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

AATCC TM22 rates the water repellency of a fabric by spraying water onto a taut specimen and comparing the wetted pattern with a photographic chart, on a scale from 0 to 100. The spray test apparatus pours a set volume of distilled water through a funnel and spray nozzle onto the specimen, held taut in a hoop at an angle. Textile mills, makers of durable water repellents (DWR) and outdoor apparel brands use the spray rating in specifications and incoming checks. The Dropometer does not measure a spray rating, so it complements the TM22 workflow and does not replace it. With the fabric holder option it measures the water contact angle and sliding angle of single drops on the fabric, which shows how well the finish repels water as made and after washing.

Why that helps: a high contact angle and a low sliding angle mean drops bead up and roll off, the behaviour a good spray rating rewards. The angles give a number for every spot, so you can rank finishes and follow wash durability between spray tests. Well finished, textured fabric can show the lotus effect, where drops rest on fibre tips and trapped air. The spray rating stays the result you report. Build the link between angles and ratings from your own fabrics.

The Dropometer contact angle and sliding angle kit reads contact angle with ±0.35° accuracy (Dropometer datasheet) and tilts samples from 0 to 60°. For the full screening workflow, see textile DWR water repellency testing. A federal research team in Canada used the Dropometer on water repellent coatings applied to white polyester fabric. Researchers also used it to measure the water contact angle of electrospun polystyrene fibre mats. For background, read the fabrics guide and the contact angle measurement guide.

Further reading: reproducible contact angle measurement, choosing a contact angle goniometer for industrial QA and the production line, why you need dynamic surface tension, a classroom experiment that makes superhydrophobic glass with a flame and our open reference measurement dataset.

How the Dropometer fits before the AATCC TM22 spray test

A contact and sliding angle screen on fabric, run before the AATCC TM22 spray test

From finished fabric to a ranked shortlist for the spray tester

These steps describe a Dropometer screen that sits before and after the spray test. They are not the AATCC TM22 procedure and do not replace it. Buy the current edition and run it on a spray tester for any spray rating you report.

±0.35°

Contact angle accuracy

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

0 to 60°

Tilt stage for sliding angle

Manual tilt as standard, automatic sliding stage as an add-on. Fabric holder option keeps the fabric flat.

About 2 min

Setup

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

1

Cut and condition the fabric

Cut pieces from the same lot you will spray test, and mark the face side and the warp direction. Handle them by the edges. Condition them in the same textile atmosphere you use for the spray test.

2

Mount it in the fabric holder

Clamp the piece flat and taut in the fabric holder, face side up. Loose or puckered fabric tilts the baseline and changes the angle. Level the base plate, mount the phone and LED, and fill the syringe with deionised water.

3

Read the water contact angle

Place a drop of fixed volume gently on the fabric and capture it at a fixed time after placement. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. On textured fabric this is an apparent angle; see the lotus effect.

4

Tilt for the sliding angle

Tilt the stage slowly until the drop rolls off, and record that angle. Use the same drop volume every time, because larger drops slide sooner. A drop that has not moved by 60°, the end of the tilt stage, is recorded as 60° or more.

5

Repeat across spots and wash cycles

Read several spots in warp and weft directions, as made and after each laundering or abrasion step your customer specifies. Rinse well after washing, because detergent left in the fabric lowers both angles.

6

Confirm with the spray test

Send the shortlisted fabrics to the AATCC TM22 spray tester and record the rating next to the angles. Over time these pairs become your own correlation, which sets the screen limits. See textile DWR water repellency testing.

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. Contact angle accuracy is ±0.35° (Dropometer product specification).

Read the validation papers

Customer evidence

A federal research team in Canada used the Dropometer on water repellent coatings applied to white polyester fabric. We have no published client study that pairs Dropometer angles with AATCC TM22 spray ratings.

Read the case study

Build your own link between angles and spray ratings

AATCC TM22 · spray rating · DWR fabric screening

AATCC TM22 rates the wetted pattern against a photographic scale (source: AATCC, The Art of Testing: Water Repellency). In summary: 100 is no sticking or wetting of the upper surface, 90 is slight random sticking or wetting, 80 is wetting at the spray points, 70 is partial wetting of the whole upper surface, 50 is complete wetting of the upper surface and 0 is complete wetting of both surfaces (source: rating descriptions quoted in US patent 8329255).

No published table converts a contact angle or sliding angle into a spray rating. So set your screen limits from your own correlation study. Run the spray test and the Dropometer on the same fabrics, as made and after washing, then pick the angles that separate the ratings your customers accept from the ones they reject.

Repeat the study when you change fibre, weave, finish chemistry or curing. Follow reproducible contact angle measurement practice so the angles are comparable between shifts and sites.

Example output

Example data for illustration only. These are not measured results. Your own fabric, finish and wash routine decide the numbers.

Example: DWR finished polyester fabric, as made and after washing

Fabric and wash state Contact angle, mean of 5 (°) Sliding angle, mean of 5 (°) Spray rating, TM22 (example lab result) Reading
Finish A, as made148.512100Beads and rolls off: send to spray test
Finish A, after 10 washes141.22490Still repellent, drops roll later
Finish A, after 20 washes132.84880Finish wearing: check cure and wash routine
Finish B, after 20 washes121.460 or more (no slide)70Drops pin: below example screen limit

How to read this table

Each angle is the mean of five drops in the fabric holder. Sliding angle is read on the tilt stage; a drop that has not moved by 60° is recorded as 60° or more. The spray rating column is an example lab result from a separate AATCC TM22 spray tester, not a Dropometer reading.

Example output chart

The same example data as the table: contact angle falls and sliding angle rises as the finish wears, in step with the example spray ratings.

Grouped bar chart of example water contact angles falling from 148.5 to 121.4 degrees and sliding angles rising from 12 to 60 degrees or more across four DWR fabric samples as the finish wears

Example data, not measured results.

Business impact

What changes when an angle screen sits before the spray tester

Metric Before Dropometer With Dropometer Results
Result format A rating in steps from 0 to 100, read by eye against a chart A contact angle per drop with ±0.35° accuracy, plus a sliding angle AATCC TM22 listing; Dropometer product specification
Small changes in the finish Can stay inside one rating step Show as a trend in angle across wash cycles No published benchmark
Material per check A full specimen on the spray hoop A small piece in the fabric holder, several spots No published benchmark
Reported TM22 result Spray tester Still the spray tester AATCC TM22 scope

See the measurement on your own fabric

Bring a fabric that rates well and one that does not, as made or after washing. We will measure both live.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of the repellency failures this screen 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 repellency screening

Lock these before you compare angles between finishes, wash cycles or sites

Parameter Recommended Setting Technical Rationale
Test liquid Deionised water Close to the distilled water the spray test uses. Oils and water alcohol mixtures belong to other repellency tests.
Mounting Fabric holder, flat and taut, face side up Loose fabric tilts the baseline and changes both angles.
Drop volume Fixed for every drop and recorded Sliding angle depends strongly on drop size, and contact angle less so.
Reading time Fixed time after placement, the same for every drop Drops can sink into a worn finish. The 10 frames per second camera suits readings from about 0.1 s.
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.
Sliding angle Tilt stage 0 to 60°; no slide recorded as 60° or more 60° is the end of the tilt stage (Dropometer datasheet).
Spots and direction Several spots, warp and weft Weave and yarn texture change the apparent angle.
Wash state As made and after each wash or abrasion step Durability, not the fresh finish, is usually what the customer buys.
Environment Condition as for the spray test; record room temperature and humidity The Dropometer has no temperature or humidity control and runs at 10 to 45 °C.

Is AATCC TM22 the right test?

Pick the method by the question you need answered

Start: What do you need to know about the fabric's water repellency?

A spray rating for a spec or customer

Signals:

Your specification, label or customer asks for an AATCC TM22 spray rating.

Rule-out:

Run AATCC TM22 on a spray tester. The Dropometer does not give a spray rating; it complements the test.

Ranking finishes and wash durability

Signals:

You want a number per spot to compare recipes, cure settings or wash cycles before spray testing.

Rule-out:

Measure water contact angle and sliding angle on the Dropometer with the fabric holder, then confirm the shortlist with TM22. See textile DWR water repellency testing.

Oil or water alcohol repellency grade

Signals:

You need a grade for resistance to oily or alcohol based liquids.

Rule-out:

Use AATCC TM118 or AATCC TM193. Contact angle with the same liquids can add a measured value.

Water passing through the fabric

Signals:

You need to know if rain or pressure pushes water through, not just whether the surface wets.

Rule-out:

Use a penetration test such as the AATCC TM42 impact penetration test, a hydrostatic pressure test or a rain test. ISO states its spray test does not predict rain penetration.

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 AATCC TM22 spray test, a contact and sliding angle screen on the Dropometer, AATCC TM118 or TM193 drop tests, and a water penetration test

Is AATCC TM22 the right test?

Interpreting angles next to the spray test rating

What contact and sliding angle tell you about a spray rating, and what they do not

High angle, low slide: good repellency: Drops that bead up and roll off early are what a high spray rating rewards.
Sliding angle moves first: As a finish wears, drops often start to pin before the contact angle falls far. Track both.
Angles are not a rating: No published table turns an angle into a spray rating. Your own paired data sets the screen limits.
Texture lifts the angle: Fabric gives an apparent angle that reflects weave and roughness as well as chemistry. Compare like fabrics.
Expert perspective

Why drop angles explain a spray rating but do not replace it

On a real surface, the receding angle from a sessile drop and from a tilted plate can disagree wildly: one method is not a substitute for the other. The application decides.

Dr. Alidad Amirfazli

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

Common pitfalls and limits next to the spray tester

Honest limits of the method and of the Dropometer

The Dropometer does not give a spray rating. Report AATCC TM22 ratings from a spray tester.
Spray drops hit the fabric at speed; a placed drop does not. A finish can bead placed drops and still wet under spray.
The camera runs at 10 frames per second. That suits a reading at a fixed time, not the moment a spray drop lands.
The tilt stage ends at 60°. Drops that have not slid by then are recorded as 60° or more.
The Dropometer has no temperature or humidity control. Condition fabric as for the spray test and record room conditions.
Detergent left after washing lowers both angles and the spray rating. Rinse and dry the same way every time.
FAQ

Frequently asked questions

What does AATCC TM22 measure?

It measures how well a fabric resists surface wetting by water. Water is sprayed onto a taut specimen held at an angle, and the wetted pattern is compared with a photographic chart. The result is a spray rating from 0 to 100. The test method is applicable to any textile fabric, with or without a water repellent finish.

What do AATCC TM22 spray ratings mean?

100 means no sticking or wetting of the upper surface. 90 is slight random wetting, 80 is wetting at the spray points and 70 is partial wetting of the whole upper surface. 50 is complete wetting of the upper surface and 0 means both surfaces are wet. Your customer sets the pass rating, often before and after washing.

Can the Dropometer run AATCC TM22?

No. AATCC TM22 reports a visual spray rating from a spray tester, and the Dropometer does not measure that rating. It complements the workflow: with the fabric holder option it measures water contact angle and sliding angle, which show why a fabric beads or wets. Use it to screen finishes and wash cycles, then confirm with the spray test. See textile DWR water repellency testing.

Can contact angle predict a spray rating?

Only through your own data. No published table converts an angle into a spray rating, and spray drops land with force that a placed drop does not have. Measure the same fabrics both ways, as made and after washing, and set screen limits from those pairs.

Why measure sliding angle as well as contact angle?

A high contact angle shows drops bead up. A low sliding angle shows they also roll off, which is what keeps the surface dry under spray. As a finish wears, drops often start to pin before the contact angle falls far, so sliding angle can show wear earlier.

Is AATCC TM22 the same as ISO 4920?

They are close relatives: both spray water onto a taut fabric and rate surface wetting by eye. They come from different bodies and report on their own scales. Check which designation your customer names and quote that one. ISO notes that its spray test does not predict rain penetration (source: ISO 4920:2012).

Can I get the surface energy of a DWR finish?

Yes, with care. The Dropometer software calculates surface free energy with the Equation of State, Fowkes and van Oss Chaudhury Good models. OWRK (Owens Wendt Rabel Kaelble) and Wu are not built in: measure the angles with the Dropometer and run OWRK in the free Contact Angle to Surface Energy Calculator. Measure on a smooth film of the finish, because fabric texture distorts the angles these models need.

Does the spray test still apply to PFAS free DWR finishes?

Yes. AATCC TM22 rates surface wetting whatever the chemistry, so it applies to fluorinated and non fluorinated DWRs alike. With the ongoing move towards non fluorinated chemistries, away from long chain perfluoroalkyl and polyfluoroalkyl substances such as PFOA and PFOS, labs compare alternative chemistries on spray rating, durability of the repellent after home laundering, and water contact and sliding angle. Water repellency often holds up better than oil repellency after the switch, so check both if your product needs it.

Legal note

This page summarises AATCC TM22 in our own words and does not reproduce the standard. Buy the current edition from AATCC before you write a procedure. The Dropometer complements the workflow: it measures contact angle and sliding angle on fabric, not the spray rating the standard specifies. Droplet Lab does not certify compliance. Your own method validation does.

View the official standard Book a 15 minute demo

How this page was created

Sources, review and tools

Transparency 4 checklist items
01

Sources

AATCC TM22-2024 listing (AATCC store); AATCC TM22 listing and apparatus (AATCC store); AATCC: The Art of Testing, Water Repellency; ISO 4920:2012 listing, Textile fabrics: resistance to surface wetting (spray test), the Dropometer product specification and Droplet Lab validation papers.

02

Drafting assistance

Drafted with Claude (Anthropic) from the sources listed, then reviewed by Droplet Lab.

03

What we did not do

We did not copy text from the standard. Buy the current edition for the full procedure.

04

Last checked

October 2026

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References

1. AATCC TM22-2024. members.aatcc.org/store/tm22/487
2. AATCC TM22 listing and apparatus (AATCC store). members.aatcc.org/store/tm22/
3. AATCC: The Art of Testing, Water Repellency. aatcc.org/the-art-of-testing-water-repellency/
4. ISO 4920:2012 listing, Textile fabrics: resistance to surface wetting (spray test). iso.org/standard/50706.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/