Contents
Partially compliant

EN 15802: static water contact angle on stone and treated heritage surfaces

EN 15802 shows how well stone, brick, mortar and other porous heritage materials shed water by reading the static water contact angle. The Dropometer reads that angle from 10° to 175° with ±0.35° accuracy (product specification), so it covers most treated surfaces. Untreated stone often absorbs the drop or reads below 10°: record those drops as below range.

What brings you here?

Who this is for
Conservation scientists, conservators, testing labs and makers of water repellents and consolidants for stone, brick, mortar and plaster.
Compliance tier
Partially compliant: the Dropometer reads static water contact angles from 10° to 175°, not untreated stone that absorbs the drop or reads below 10°.
Measurement
Sessile drop static water contact angle, 10° to 175° range, ±0.35° accuracy (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs in the lab or a site workroom.
Last updated
October 18, 2026
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Free one page checklist for EN 15802: what to prepare, the settings to lock, how to time the reading on absorbing stone and what to record. Made for conservation and treatment testing labs.

Talk to an expert

Book a 15 minute demo on your stone

Tell us your stone, treatment and current check. We will measure live and tell you plainly which part of EN 15802 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 EN 15802
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

EN 15802:2009, Conservation of cultural property: test methods: determination of static contact angle, from CEN/TC 346. National editions such as UNI EN 15802:2010, SIST EN 15802:2010 and BS EN 15802:2009 (published January 2010) are identical. See the BSI listing.

Compliance tier

Partially compliant. The Dropometer measures the static water contact angle on porous specimens from 10° to 175°. Untreated or weakly treated stone can absorb the drop or read below 10°, outside that range, so those drops are recorded as below range.

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

We have no published client paper on stone or heritage materials yet. For typical values on other materials, see water contact angle reference values.

What it does not tell you

A high angle shows the surface sheds water at the moment of reading. It does not show how deep a treatment went, how much water the stone takes up over hours, or whether it still lets vapour out. Pair it with absorption and permeability tests.

Executive summary

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

EN 15802 measures the static contact angle of a water drop on porous inorganic materials used in cultural property, such as stone, brick, mortar and plaster, whether untreated, treated or aged. Conservation scientists, conservators and suppliers of water repellents use it to compare treatments and to follow how they age. The Dropometer is partially compliant: it reads the static water contact angle from 10° to 175° with ±0.35° accuracy (product specification), but untreated stone often absorbs the drop or reads below 10°, outside that range.

The method places a drop of water on the specimen and reads the angle from the drop profile at a set time. On porous stone the drop soaks in, so the angle falls with time and the reading time matters as much as the angle. For the term itself, see the contact angle glossary entry. For the method in depth, read the contact angle measurement guide.

The Dropometer contact angle and surface energy kit runs on battery and captures drop images at 10 frames per second. That suits a reading at a fixed time, such as several seconds after the drop lands, but not millisecond absorption studies. For wider context on building materials, read our construction guide. To keep results comparable between operators and labs, follow our notes on reproducible contact angle measurement.

Further reading: water contact angle reference values for common surfaces, choosing a contact angle goniometer for industrial QA and the Leidenfrost effect, or why drops skate on very hot surfaces.

How the Dropometer fits the workflow

The EN 15802 measurement, step by step, in our own words

From conditioned specimen to a timed angle

These steps outline the procedure and show where the Dropometer reaches its limit. They do not replace the standard. Buy the current edition and follow its drop volume, reading time and specimen rules.

±0.35°

Contact angle accuracy

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

10° to 175°

Measuring range

Untreated stone can absorb the drop or read below 10°. Record those drops as below range.

10 fps

Camera speed

10 frames per second: fine for a reading at a set time, not for millisecond absorption studies.

1

Prepare and condition the specimens

Cut or select specimens with a flat, level test face. Note the stone, the treatment, the application date and any ageing step. Use the number, size and pre conditioning the standard specifies, so the stone holds the same moisture for every test.

2

Set up the Dropometer

Place the base plate on a level bench, mount the phone and LED, and fill a clean syringe with water of the grade the standard specifies. Lay the specimen flat on the sessile stage, test face up. Use the automatic dropper add-on (down to 0.05 µL) or the manual dropper (5.29 µL per rotation) to set the drop volume.

3

Place the drop and start capture

Dispense the drop volume the standard specifies onto a fresh area, without touching the stone with the needle. Start the app's multi capture as the drop lands, so you have a series of images at 10 frames per second and a known time zero.

4

Read the angle at the set time

Read the angle from the image at the reading time the standard specifies. Automatic edge and baseline detection reads the left and right angles, so two operators get the same reading from the same image. If the drop has soaked in or reads below 10°, record it as not measurable or below range.

5

Repeat across the surface

Place drops at several positions on each specimen. Stone varies in porosity and treatments soak in unevenly, so one drop is not enough. Studies that cite EN 15802 report 15 positions per specimen (Materials, 2018).

6

Record and compare

Record the mean, spread, reading time, number of drops below range, treatment, ageing step and room conditions. Compare the mean with your own limit. For habits that keep results comparable, see reproducible contact angle measurement.

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

We have no published client paper on stone or heritage materials yet. Our open data set lists water contact angles on common surfaces, so you can see what typical values look like before you test your own stone.

See the reference values

Set your limits from your own stone

EN 15802 · water repellency · treatment testing

The public listings of EN 15802 give no pass or fail angle (source: BS EN 15802:2009 listing). Many conservation studies treat 90° as the line between hydrophilic and hydrophobic behaviour (for example, a 2024 study of hydrophobic coatings on limestone). Use that as a reference line, not as a specification.

Set your own limit from a correlation study. Measure untreated, treated and aged specimens of the same stone, at the same reading time, and compare the angles with how well each specimen keeps water out, for example by capillary absorption to EN 15801. Pick the angle that separates good from poor performance.

Check where your results sit against the Dropometer range of 10° to 175°. Treated stone usually reads well inside it. Untreated or weakly treated stone can read below 10° or absorb the drop before the reading time: record those drops as below range or not measurable, and do not report a value for them. Repeat the study when you change the stone, the product, the application rate or the ageing method.

Example output

Example data for illustration only. These are not measured results. Your own stone, treatment, ageing method and limits decide the numbers.

Example: porous limestone, untreated and with two water repellents, before and after ageing

Specimen Drops (n) Mean angle at reading time (°) Std dev (°) Decision
Untreated limestone15Absorbed or below 10 (below range)n/aNot measurable: expected for untreated stone
Water repellent A15128.43.1Accept
Water repellent A, after ageing15121.93.8Accept
Water repellent B15104.64.2Accept
Water repellent B, after ageing1582.75.6Below 90°: review the treatment

How to read this table

Each row is the mean of 15 drops read at the same set time after deposition. The decision column uses an example limit of 90° or higher, a reference line many conservation studies use; set yours from your own correlation study. The untreated stone absorbed the drops or read below 10°, outside the Dropometer range, so no value is given.

Example output chart

The same example data as the table, plotted against the example 90° limit and the bottom of the Dropometer range. The untreated stone is left out because it absorbed the drops or read below 10°.

Bar chart of example water contact angles on limestone treated with two water repellents, fresh and after ageing, with a 90 degree example limit and the 10 degree bottom of the Dropometer range marked

Example data, not measured results.

Business impact

What changes when water repellency is a timed, measured angle

Metric Before Dropometer With Dropometer Results
How the check is made Drop beading judged by eye Static water contact angle read from the drop image No published benchmark
Result format Description or photo An angle per drop, 0.01° display, ±0.35° accuracy Dropometer product specification
Timing on absorbing stone Reading time estimated by hand Image series at 10 frames per second from the moment the drop lands Dropometer product specification
Untreated stone below 10° Lab goniometer rated for low angles Recorded as below range or not measurable Dropometer range 10° to 175°, product specification

See the measurement on your own stone

Bring an untreated and a treated specimen of the same stone. We will measure both live and show how the angle changes with time.

Book a 15 minute demo Request a quote
ROI estimate

Estimate the cost of water repellent treatments that fail early

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 treatments, ageing steps or labs

Parameter Recommended Setting Technical Rationale
Test liquid Water, of the grade the standard specifies This is a water contact angle method. Impure water gives false readings.
Drop type Sessile drop, static angle The method reads a drop resting on a level test face.
Drop volume As the standard specifies, fixed for every drop Studies citing EN 15802 report 5 µL drops. A changing volume changes how fast the drop soaks in.
Reading time As the standard specifies, fixed for every drop On porous stone the angle falls as water soaks in. Studies citing the standard report 10 s or 30 s.
Capture Multi capture at 10 frames per second from deposition Gives a known time zero and lets you check the angle at the set time.
Measuring range 10° to 175°; record lower or absorbed drops as below range Dropometer product specification. Untreated stone often reads below 10°.
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 The Dropometer runs at 10 to 45 °C and has no temperature or humidity control.

Is EN 15802 the right test?

Pick the method by the question you need answered

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

Water repellency of a treated surface

Signals:

You want a measured angle to compare treatments or ageing steps on the same stone.

Rule-out:

Use EN 15802, this page. The Dropometer is partially compliant and covers angles from 10° to 175°.

How much water untreated stone takes up

Signals:

The drop soaks in before the reading time, or you need uptake over minutes or hours.

Rule-out:

Use a water absorption test such as capillary absorption to EN 15801. A contact angle cannot give a value here.

Whether roughness changed

Signals:

A treatment, cleaning or weathering step may have changed the surface texture.

Rule-out:

Measure areal roughness to ISO 25178. Roughness also shifts the apparent angle.

Surface free energy of the treated face

Signals:

You need to know why a coating, mortar or adhesive does or does not bond to the stone.

Rule-out:

Measure angles with two or more liquids, as in DIN EN 828. The Dropometer runs this on non absorbing surfaces.

Decision tree at a glance

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

Decision tree for choosing between EN 15802 static water contact angle, EN 15801 capillary absorption, ISO 25178 roughness and a DIN EN 828 surface free energy method

Is EN 15802 the right test?

Interpreting results

What the angle tells you, and what it does not

Higher angle, more water repellent: A good water repellent makes water bead up on stone, so the angle rises well above that of the untreated surface.
A falling angle means absorption: If the angle drops between the first image and the reading time, water is soaking in. Note the rate as well as the angle.
Spread across the surface matters: A good mean with a few low drops points to uneven application or a more porous patch of stone.
Angle is not durability: A fresh treatment can read high and still fade. Compare fresh and aged specimens at the same reading time.
Expert perspective

Why the outermost layer decides how stone takes up water

What a liquid responds to is only the outermost few ångström of a surface: the skin, not the bulk. Change that skin and you change the wetting, even if the material underneath is identical.

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

Untreated stone often absorbs the drop or reads below 10°, outside the Dropometer range. Record it as below range, not as a value.
On porous stone the angle changes with time. A reading at the wrong time is a different result, so fix and record the time.
Rough or weathered faces give an apparent angle that reflects texture as well as chemistry. Compare like with like.
Sessile drop needs a level test face. Vertical walls on site need a specimen, or a different test for water uptake.
The Dropometer has no temperature or humidity control, and its camera runs at 10 frames per second. Record room conditions and read at a fixed time.
FAQ

Frequently asked questions

What does EN 15802 measure?

It measures the static contact angle of a water drop on porous inorganic materials used in cultural property, such as stone, brick and mortar. It applies to untreated, treated and aged materials. Conservation labs use it mainly to compare water repellent treatments and to follow how they age.

Is EN 15802:2010 a different edition from EN 15802:2009?

No. CEN published EN 15802 in December 2009. National bodies then issued identical editions, such as UNI EN 15802:2010 in Italy and SIST EN 15802:2010 in Slovenia, which is why both years appear. See the BSI listing.

Can the Dropometer run EN 15802?

In part. The Dropometer measures the static water contact angle on porous specimens from 10° to 175° with ±0.35° accuracy (product specification). That covers most treated stone. Untreated stone often absorbs the drop or reads below 10°, outside that range, so record those drops as below range.

What drop volume and reading time does EN 15802 use?

Follow your copy of the standard. Studies that cite EN 15802 report 5 µL drops read 10 s after deposition (Materials, 2018), and a 2025 study states the standard sets 30 s (iScience, 2025). Both are well within a camera running at 10 frames per second.

What water contact angle shows a stone is water repellent?

The public listings give no pass or fail angle. Many conservation studies use 90° as the line between hydrophilic and hydrophobic, for example this 2024 limestone study. Set your own limit from a correlation study on your stone, fresh and aged.

Why does the contact angle on stone fall over time?

Porous stone draws water in through its pores, so the drop shrinks and the angle drops. Evaporation adds to this. That is why EN 15802 fixes a reading time. The Dropometer app's multi capture records images at 10 frames per second, so you can read the angle at the set time and see the trend.

Is a contact angle enough to judge a water repellent?

No. A high angle shows the surface sheds water at the moment of reading. It does not show how much water the stone takes up over time or whether vapour can still escape. Pair EN 15802 with a water absorption test such as EN 15801.

Legal note

This page summarises EN 15802 in our own words and does not reproduce the standard. Buy the current edition from your national standards body before you write a procedure. The Dropometer is partially compliant with this method. 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

BSI Knowledge: BS EN 15802:2009 listing (current, identical to EN 15802:2009); iTeh: EN 15802:2009 listing (CEN/TC 346, scope, contents); UNI: UNI EN 15802:2010 listing (in force since 4 February 2010); EN 15801:2009 listing (capillary water absorption), 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. EN 15802:2009 / UNI EN 15802:2010. knowledge.bsigroup.com/products/conservation-of-cultural-property-test-methods-determination-of-static-contact-angle
2. iTeh: EN 15802:2009 listing (CEN/TC 346, scope, contents). iteh.es/catalog/standards/cen/a93aafde-6380-4bc5-9d9b-d3b535dee619/en-
3. UNI: UNI EN 15802:2010 listing (in force since 4 February 2010). store.uni.com/uni-en-15802-2010
4. EN 15801:2009 listing (capillary water absorption). shop.standards.ie/en-ie/standards/en-15801-2009-335478_saig_cen_cen_77
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/