Contents
Partially compliant

ASTM D3825-90: test method for dynamic surface tension by the fast bubble technique

ASTM D3825 measured how surface tension changes in the first moments after a liquid surface forms, using fast bubbles. ASTM withdrew it in 2016. The Dropometer is partially compliant: it measures the same property, dynamic surface tension, by pendant drop, with ±0.03 mN/m accuracy. Its 10 frames per second camera reads surface ages from about 0.1 s, so it cannot reach the millisecond ages where fast bubbles work. The part it covers is the overlap from about 0.1 s onward. Pendant drop is an alternative method, not the fast bubble method the standard specifies; if a contract or customer requires an ASTM D3825 result, run a correlation study on your own samples first.

What brings you here?

Who this is for
Surfactant and coating formulators, chemical producers and process engineers who need surface tension of solutions and mixtures over time, for research and development or quality control.
Compliance tier
Partially compliant: the Dropometer measures dynamic surface tension by pendant drop, an alternative method, only from about 0.1 s onward. It cannot reach millisecond surface ages.
Measurement
Pendant drop surface tension, static and dynamic, up to 75 mN/m, ±0.03 mN/m accuracy, 10 frames per second (Dropometer datasheet).
Setup
About 2 minutes. Battery powered, 1 kg, runs in the lab or at the process.
Last updated
October 20, 2026
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Free one page checklist for pendant drop dynamic surface tension alongside ASTM D3825: what to prepare, the settings to lock, the drop ages to read and what to record.

Talk to an expert

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Tell us your liquid, surfactant and the surface ages you care about. We will measure it live and tell you plainly where pendant drop helps and where you need a bubble pressure tensiometer.

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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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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 ASTM D3825
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

ASTM D3825-09, Standard Test Method for Dynamic Surface Tension by the Fast-Bubble Technique, from ASTM Committee D02. First issued as D3825-90. ASTM withdrew it in July 2016 with no replacement. It measured the specific free energy of a liquid-gas surface shortly after the surface forms, which is dynamic surface tension.

Compliance tier

Partially compliant. The method blows bubbles through two capillaries, reads the differential pressure between them and reports surface tension against surface age in milliseconds. The Dropometer measures the same property by pendant drop, an alternative method, at surface ages from about 0.1 s, set by its 10 frames per second camera. It cannot reach millisecond ages, so the part it covers is the overlap from about 0.1 s onward.

Instrument performance

Pendant drop surface tension up to 75 mN/m, accuracy ±0.03 mN/m, resolution 0.01 mN/m, static and dynamic, 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 2025 preprint on surfactants in a nanocrystal suspension used the Dropometer as a pendant drop tensiometer for surface tension. Read our analysis.

What it does not tell you

Pendant drop does not reach millisecond surface ages. For those, use a bubble pressure tensiometer. For tension between two liquids, the Dropometer measures interfacial tension by pendant drop with the optional cuvette.

Executive summary

What this standard measured, who used it and how the Dropometer fits

ASTM D3825 measured dynamic surface tension by the fast bubble technique: the pressure needed to blow bubbles at a capillary tip, read at a series of bubble rates to give surface tension against surface age. It was written for liquid mixtures in which one component moves to the surface, and for physical properties data used to design equipment such as distillation towers. Coating formulators care about the same property, because surfactants are used to help a coating wet the substrate to be coated in a fraction of a second. ASTM withdrew the last edition, D3825-09, in 2016 with no replacement. The Dropometer is partially compliant: it measures the same property, dynamic surface tension, by pendant drop rather than fast bubbles, and only from about 0.1 s onward.

The fast bubble method reports surface age in milliseconds, so its fast end sits below what the Dropometer's 10 frames per second camera can resolve. The part the Dropometer covers is the overlap from about 0.1 s onward: the later part of the curve, from a tenth of a second to minutes, and the equilibrium value. For millisecond ages, use a bubble pressure tensiometer. For the terms used, see the time resolved pendant drop glossary entry and why you need dynamic surface tension.

The Dropometer pendant drop tensiometer reads surface tension up to 75 mN/m with ±0.03 mN/m accuracy, on battery, in the lab or at the process. Formulators use the same readings for CMC assessment and surfactant efficiency. A 2025 preprint on surfactants in a nanocrystal suspension used the Dropometer for pendant drop surface tension. See also the university rheology lab case study on pendant drop surface tension.

Further reading: the surface tension measurement guide, the chemicals guide, reproducible surface tension measurement, choosing a tensiometer for dynamic surface tension, CMC reference values for common surfactants and a classroom experiment on how surfactants lower surface tension.

How the Dropometer fits: measure surface tension over time

How ASTM D3825 worked, and the pendant drop workflow for the part the Dropometer covers

From liquid sample to a surface tension curve over time

These steps outline a pendant drop dynamic surface tension run and show where it differs from the fast bubble method. They do not replace the standard. If a customer still names ASTM D3825, agree the method with them in writing first.

±0.03 mN/m

Surface tension accuracy

From the Dropometer product specification. Resolution is 0.01 mN/m, range up to 75 mN/m.

10 fps

Camera frame rate

First reading about 0.1 s after the drop forms. The fast bubble method works in milliseconds.

About 2 min

Setup

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

1

Decide which surface ages you need

List the drop ages that matter for your process, for example 0.1, 1, 10 and 100 s. If you need ages below about 0.1 s, use a bubble pressure tensiometer for that part. ASTM D3825 worked in that millisecond range.

2

Prepare and condition the liquid

Let the liquid reach room temperature and note its density at that temperature. The fast bubble method held its bubbler in a water jacket, with a default test temperature of 25 ± 0.1 °C. The Dropometer has no temperature control, so record room temperature.

3

Check the setup with water

Clean the needle and syringe, then measure the surface tension of water and compare with its reference value at room temperature. A low reading points to contamination. See reproducible surface tension measurement.

4

Form the drop and start the clock

Start capture, then form a pendant drop of the same size each time. Take the first frame with the full drop as time zero. At 10 frames per second, time zero is known to within about 0.1 s.

5

Read surface tension over time

Read the Young-Laplace fit at each chosen drop age until the value levels off. Automatic edge detection gives the same reading from the same image. Repeat with fresh drops, three or more per sample.

6

Record and report the method

Record the values at each drop age, room temperature, density, needle and drop size. Report the method as pendant drop, not ASTM D3825. For background, see time resolved pendant drop.

7

Watch the full measurement

This video shows a complete Dropometer pendant drop surface tension measurement, from setup to result. It covers the steps above in one run.

Dropometer pendant drop surface tension, 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 surface tension accuracy is ±0.03 mN/m.

Read the validation papers

Customer evidence

We have no published client work to ASTM D3825 or by fast bubbles. A 2025 preprint on surfactants in a nanocrystal suspension used the Dropometer for pendant drop surface tension.

Read our analysis

Set limits for each surfactant formulation

ASTM D3825 · surface age · correlation study

ASTM D3825 calibrated its bubbler with five liquids of known surface tensions, water, ethanol or methanol, acetone and toluene, to get one apparatus constant (source: ASTM D3825-09 listing and preview). It is a property method for design data, and its public summary gives no pass or fail value.

Pendant drop needs no apparatus constant from reference liquids. It needs the needle diameter for scale and the liquid density at test temperature. Check the setup with water before each session, and log the result.

Set accept limits from your own correlation study. Measure lots that performed well and lots that failed, at the same drop ages, then set limits at those ages. If you must compare with fast bubble data, run both methods on the same samples first. Bubble and drop results at the same nominal age are not interchangeable without that study.

Example output: three lots of a surfactant formulation

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

Example: water check and three lots of a surfactant formulation, pendant drop

Sample At 0.1 s (mN/m) At 1 s (mN/m) At 10 s (mN/m) At 100 s (mN/m) Reading
Water check72.272.272.172.1Steady: needle and syringe clean
Lot A (reference)52.441.634.833.1Reference curve
Lot B53.042.335.233.3Within 2.0 mN/m at 1 s and 10 s: accept
Lot C63.555.141.933.4Same end value, much slower: check the surfactant

How to read this table

Each value is the mean of three drops at that drop age. The reading column uses an example rule: within 2.0 mN/m of the reference lot at 1 s and 10 s, set from a correlation study. Readings at about 0.1 s carry up to 0.1 s of timing uncertainty.

Example output chart

The same example data as the table, plotted from 0.1 s to 100 s on a log scale. Lot C ends at the same value as the reference but gets there much more slowly.

Line chart of example surface tension from 0.1 to 100 seconds for a water check and three formulation lots, with lot C falling much more slowly to the same end value

Example data, not measured results.

Business impact

What changes when you can read the later part of the curve at the bench

Metric Before Dropometer With Dropometer Results
Where the check runs Bubble pressure tensiometer in a central lab At the bench or the process, on battery for up to 8 h Dropometer product specification
Surface ages covered Milliseconds and up, by fast bubbles About 0.1 s to equilibrium, by pendant drop ASTM D3825-09 terminology; Dropometer product specification
Result format Equilibrium value only, if no dynamic tester A value at each drop age, 0.01 mN/m resolution, ±0.03 mN/m accuracy Dropometer product specification
Millisecond surface ages Bubble pressure tensiometer Still needs the bubble pressure tensiometer Dropometer camera runs at 10 frames per second

See the measurement on your own liquid

Bring two lots: one that performed well and one that did not. We will measure both live from about 0.1 s to equilibrium.

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ROI estimate

Estimate the cost of the wetting and foaming problems 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 results between shifts or sites

Parameter Recommended Setting Technical Rationale
Method Pendant drop, reported as such Pendant drop is an alternative method, not the fast bubble method ASTM D3825 specifies.
Drop ages Fixed list, for example 0.1, 1, 10 and 100 s Compare lots at the same ages. Ages below about 0.1 s are out of reach at 10 frames per second.
Time zero First frame with the full drop There is no bubble timing signal, so time zero carries up to 0.1 s of uncertainty.
Liquid density Measured or looked up at room temperature The Young-Laplace fit needs density. A wrong density shifts every value.
Needle and drop size Same needle and drop size for every run Drop size changes how fast surfactant reaches the surface, so keep it fixed.
Fit model Young-Laplace Pendant drop surface tension comes from the Young-Laplace fit of the drop profile.
Replicates Three or more fresh drops per sample Shows the spread at each drop age and catches a contaminated drop.
Temperature Record room temperature for every run The Dropometer has no temperature control and runs at 10 to 45 °C. The standard recommended 25 ± 0.1 °C.

Is ASTM D3825 the right test method?

Pick the method by the surface age you need

Start: What do you need to know about your liquid's surface tension?

Surface tension within the first 0.1 s

Signals:

You need millisecond surface ages, for example for fast spraying, foaming or coating processes, or to match old ASTM D3825 data.

Rule-out:

Use a bubble pressure tensiometer. ASTM D3825 is withdrawn; ISO 22706, a bubble pressure method for paints and varnishes, is still in draft at ISO.

How surface tension falls from 0.1 s to minutes

Signals:

You want to see how fast a surfactant reaches the surface over seconds to minutes.

Rule-out:

Use pendant drop to measure the dynamic surface tension. The Dropometer runs this measurement.

Equilibrium value or CMC

Signals:

You need the end value of a surfactant solution, or the concentration where it stops falling.

Rule-out:

Use pendant drop at equilibrium, as in CMC assessment, or the du Noüy ring and plate methods in EN 14370.

Tension between two liquids

Signals:

You need the tension between a surfactant solution and an oil, not against air.

Rule-out:

The Dropometer measures interfacial tension by pendant drop of one liquid in another with the optional cuvette. That is an alternative method to the ones in EN 14210 and ISO 6889.

Decision tree at a glance

Start from the surface age or quantity you need. Blue boxes are measurements the Dropometer runs.

Decision tree for choosing between a bubble pressure tensiometer for millisecond surface ages, pendant drop dynamic and equilibrium surface tension on the Dropometer, and pendant drop with the optional cuvette for tension between two liquids

Is ASTM D3825 the right test?

Interpreting dynamic surface tension curves

What a surface tension curve over time tells you, and what it does not

A falling curve means surfactant is arriving: Surface tension drops as surfactant moves to the new surface and starts to lower the surface tension. A steeper early fall means a faster surfactant with high surface activity.
Same end value, different speed: Two lots can reach the same equilibrium value at different rates. Only readings over time show that.
Bubble age is not drop age: A bubble surface and a drop surface form and stretch differently. Even in the overlap from about 0.1 s onward, compare methods only through your own correlation study.
Mixtures can shift as they evaporate: In volatile mixtures the surface layer can change as one component leaves. Read promptly and record room conditions.
Expert perspective

Why surface tension changes in the first seconds

Plot surface tension against surfactant concentration and the interface tells you when it is saturated: the curve bends at the point where the surface can hold no more.

Dr. Alidad Amirfazli

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

Common pitfalls and limits for coating liquids

Honest limits of the method and of the Dropometer

The camera runs at 10 frames per second, so the Dropometer covers only the overlap from about 0.1 s onward, not millisecond surface ages.
The Dropometer has no temperature control. Condition the liquid, record room temperature and stay within 10 to 45 °C.
Volatile, low surface tension liquids such as solvent blends evaporate from a hanging drop. Keep the drop out of drafts and read it promptly.
Surface tension range is up to 75 mN/m, so liquids with a high surface tension above that need another instrument. Hot liquids are also out of scope: the Dropometer runs at 10 to 45 °C.
Traces of surfactant on the needle or syringe lower the reading. Check with water before each session.
FAQ

Frequently asked questions

What does ASTM D3825 measure?

It measures dynamic surface tension: the surface tension of a liquid a short time after its surface forms. Gas is blown through capillaries at several rates, and the maximum pressure in the bubbles is measured to give surface tension at each surface age, in milliseconds. It was aimed at mixtures where one component moves to the surface.

Is ASTM D3825 still an active standard?

No. It is no longer among the active ASTM standards: ASTM withdrew the last edition, D3825-09, in July 2016 for lack of interest in maintaining it, and named no replacement. Older specifications and papers may still cite D3825-90. If a customer names it, agree the method and any deviations with them in writing.

Can the Dropometer run ASTM D3825?

Partly. The Dropometer measures dynamic surface tension, the property ASTM D3825 reports, but only at surface ages from about 0.1 s, because its camera runs at 10 frames per second. It cannot reach the millisecond ages where fast bubbles work, so the part it covers is the overlap from about 0.1 s onward. Pendant drop is an alternative method, not the fast bubble method the standard specifies; if a contract or customer requires an ASTM D3825 result, run a correlation study on your own samples first.

What drop ages can the Dropometer read?

From about 0.1 s after the drop forms to many minutes, and the equilibrium value. The camera runs at 10 frames per second, so it cannot resolve millisecond surface ages. See time resolved pendant drop.

Are ASTM D3825 bubble results and pendant drop results interchangeable?

Not without a correlation study on your own liquids. A bubble surface and a drop surface form and stretch differently, so the same nominal age can give different values. Run both methods on the same samples before you compare them.

What can I use instead of ASTM D3825?

For millisecond surface ages, use a tensiometer that runs the maximum bubble pressure method. ISO 22706, a bubble pressure method for paints and varnishes, is in draft at ISO. For seconds to minutes and equilibrium values, pendant drop works. See choosing a tensiometer for dynamic surface tension.

Does the Dropometer measure interfacial tension?

Yes, with the optional cuvette. It measures interfacial tension by pendant drop of one liquid in another, for example a surfactant solution against an oil. That is an alternative method to the ring or stirrup in EN 14210. ASTM D3825 itself covers surface tension against a gas only.

Why does dynamic surface tension matter for a coating?

When a coating is applied, new liquid surface forms in a fraction of a second, and the surfactant needs time to adsorb there. In water based systems, a formulation with a good static surface tension value can still show poor surface wetting or surface defects if its surfactant is slow. Dynamic surface tension measurements show that rate. The Dropometer reads from about 0.1 s onward; faster application, such as spraying, needs a maximum bubble pressure tensiometer.

Legal note

This page summarises ASTM D3825 in our own words and does not reproduce the standard. ASTM withdrew it in 2016. The Dropometer is partially compliant: it measures dynamic surface tension by pendant drop from about 0.1 s onward and does not run the fast bubble method. 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

ASTM D3825-09 listing (withdrawn 2016, no replacement); ASTM D3825-90(2000) historical listing; ANSI webstore: ASTM D3825-09; iTeh listing for ASTM D3825-09 (withdrawal date and reason), 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. ASTM D3825-09 (withdrawn 2016). store.astm.org/d3825-09.html
2. ASTM D3825-90(2000) historical listing. store.astm.org/d3825-90r00.html
3. ANSI webstore: ASTM D3825-09. webstore.ansi.org/standards/astm/astmd382509
4. iTeh listing for ASTM D3825-09 (withdrawal date and reason). standards.iteh.ai/catalog/standards/astm/9b2a9954-65ee-49f8-b449-4f656
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/