Dropometer
US$4,990 base kit, checked 23 October 2026
Surface energy analyzer comparison
Dropometer vs dyne pens and dyne test inks
Dyne pens and dyne test inks tell you whether a plastic film or part has reached a target dyne level, for example after corona treatment, by whether the ink wets the surface or beads up. The Dropometer measures the contact angle and calculates surface energy as a number. This page compares the two for surface treatment, printing and adhesion checks.
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Dyne test pens and inks
ACCU DYNE TEST 16 pen set (30 to 60) US$108.80; single pens US$10.80 each (minimum four). Checked 23 October 2026
Written by
Abhimanyu Bhandankar
Holds an MBA from Schulich School of Business and a BE in IT. He joined Droplet Lab in July 2019 and now leads sales and marketing.
CEO at Droplet Lab
Read More
Technical Review 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
The short answer
Use dyne pens for quick pass or fail checks of treated polyethylene and polypropylene film against a known dyne level. Use the Dropometer (US$4,990) when you need a number: contact angle, surface free energy with its polar and dispersive parts, and a record you can trend, on any solid surface.
When dyne pens are the better choice
- Cost. ACCU DYNE TEST sells a 16 pen set from 30 to 60 dyn/cm for US$108.80 and single pens US$10.80 each (minimum four).
- Speed. Draw a line, watch whether the ink holds or beads, done; no instrument, power or training beyond the method.
- Established practice. ASTM D2578 covers polyethylene and polypropylene film and ISO 8296 covers plastic film and sheeting.
- Many points. Easy to check across a wide web or a large part.
When the Dropometer is the better choice
- A number, not a band. Contact angle to 0.01° resolution and surface free energy as a value, instead of a 2 dyn/cm step.
- Polar and dispersive parts. Surface free energy from several liquids explains why one ink or adhesive wets and another does not.
- Any solid. Metals, glass, coatings and composites, not only polymer film.
- No consumable to expire. Pens have a six month shelf life and need replacing.
- A record. Each result is saved as an image and a CSV value you can trend.
When not to buy a Dropometer
- A pass or fail check at one dyne level is all your process needs, and the pens are already in your work instructions.
- You test many points across a wide web or large part every shift and need no instrument at all.
- Your budget is a few hundred dollars a year: a 16 pen set costs US$108.80.
- You need audit trails or electronic signatures, which the Dropometer does not support.
Executive summary
A dyne pen applies a test ink of known surface tension. If the ink stays as a continuous film the surface's dyne level is at least that value; if it pulls into beads, it is lower. The result is a band, read by eye, in steps of about 2 dyn/cm. The Dropometer measures the contact angle of a small drop and calculates surface free energy, so you get a number with its polar and dispersive parts, saved as an image and a CSV result.
Where they overlap
Both are used to check that corona, flame or plasma treatment worked before printing, laminating or bonding. See corona treatment monitoring for print quality.
Both rest on wetting: whether a liquid of known surface tension spreads or beads on the surface.
Both are portable enough to take to the line.
Where they differ and why it matters
Output
Dyne pens give a pass or fail at the pen's dyne level. The Dropometer gives a contact angle and a calculated surface free energy.
Who reads it
A dyne test is read by eye, so two operators can call the same line differently. The Dropometer detects the drop edge and baseline automatically.
Surfaces
The test ink standards cover plastic film. The Dropometer measures any solid surface you can place a drop on.
Cost over time
A pen set costs about US$110 to US$150 and is replaced every six months. The Dropometer is US$4,990 once, with no test ink to replace.
A deeper look at the criteria that decide it
Which dyne tests we compared
- ACCU DYNE TEST marker pens: 16 pen set (30 to 60) US$108.80, 22 pen set (30 to 72) US$149.60, single pens US$10.80 each (minimum four), standard levels in 2 dyn/cm steps with 1 dyn/cm levels available; six month shelf life. ACCU DYNE TEST.
- ACCU DYNE TEST test fluids: 30 to 72 dyn/cm; five month shelf life. Test fluids.
- Dyne Testing pens to ISO 8296: 30 to 72 mN/m in 2 mN/m steps. Dyne Testing.
- Low toxicity pens: some suppliers, such as Sherman Treaters, sell pens marketed as non toxic. Sherman Treaters.
What a dyne level does and does not tell you
A dyne test measures the wetting tension of the surface against a test liquid, which tracks surface energy but is not the same thing. It also gives one total figure: two surfaces at 40 dyn/cm can bond very differently because their polar and dispersive parts differ. Read Beyond 38 dynes for what surface energy tells you about adhesion.
Ink chemistry and safety
Many test inks are mixtures of formamide and 2-ethoxyethanol, and ACCU DYNE TEST's safety data sheet for its pens carries the warning "May damage fertility". Use them with ventilation and gloves, and keep the tip clean; ACCU DYNE TEST says its valve tip guards against contamination. The Dropometer usually works with water and a few standard test liquids.
Using both
Many converters keep dyne pens on the line for quick checks and use contact angle measurement in the lab to set the treatment level and investigate failures. If you are moving from pens to measured values, start by measuring treated and untreated samples on the Dropometer. Our industrial QA buying guide compares line options.
Specification and capability matrix
| Criterion | Dyne pens and test inks | Dropometer |
|---|---|---|
| Price (checked 23 October 2026) | 16 pen set US$108.80; 22 pen set US$149.60; single pens US$10.80 each, minimum four (ACCU DYNE TEST) | US$4,990 base kit (phone and lifetime licence included) |
| What it tells you | Pass or fail against the pen's dyne level | Contact angle and calculated surface free energy |
| Resolution | Standard steps of 2 dyn/cm; 1 dyn/cm levels available | 0.01° contact angle; 0.01 mN/m surface tension |
| Polar and dispersive parts | No; one total figure | From several liquids |
| Surfaces | Plastic film and sheeting (ISO 8296); PE and PP film (ASTM D2578) | Any solid surface you can place a drop on |
| How it is read | By eye: film or beads | Automatic edge and baseline detection |
| Shelf life | About 6 months (pens), 5 months (fluids) | No consumable test ink |
| Safety | Formamide and 2-ethoxyethanol inks; reproductive toxicity warning | Water and standard test liquids |
| Dynamic angles and surface tension | No | Advancing and receding in the app; Pendant drop, up to 75 mN/m; 0.01 mN/m resolution |
| Records | Manual notes | TIFF images, CSV results; no audit trail or electronic signatures |
| Portability | Pocket size | 5 V, battery up to 8 h; 1 kg; sets up in about 2 minutes |
Checked 23 October 2026. Dyne pen figures come from ACCU DYNE TEST product and safety data pages, ASTM D2578-23, ISO 8296 and supplier pages. Dropometer figures come from the Dropometer specification.
How we built this comparison
We compared published dyne pen and test ink information, the two test standards and supplier pages with the Dropometer's specification. We have not run a side by side study for this page. Dyne pens and the Dropometer measure different things, so the page compares what each tells you rather than accuracy figures.
Disclosure: Droplet Lab makes the Dropometer, so read this page knowing that. Every competitor figure links to the maker's own page or datasheet, and where a figure is not published we say so. If your process only needs a pass or fail at one dyne level on PE or PP film, pens are the cheaper and faster tool and the verdict flips.
Expert perspective
Corona and plasma treatment change only the outermost layer of a polymer. Dr. Alidad Amirfazli explains why that thin layer decides how an ink or adhesive wets.
Only the skin of the surface counts
"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."
What this means here: both a dyne pen and a contact angle drop test only the treated skin. Measure soon after treatment, because that skin changes with time and handling.
Recommendations by scenario
Pass or fail on treated PE or PP film
Pick: dyne pens to ASTM D2578 or ISO 8296. See ASTM D2578.
Setting or troubleshooting the treatment level
Pick: Dropometer. See corona treatment monitoring.
Adhesion problems on metals, glass or coatings
Pick: Dropometer. See preventing adhesive failure before bonding.
A traceable number for quality records
Pick: Dropometer. See the industrial QA guide.
Bottom line
Dyne pens are the cheapest and fastest pass or fail check for treated film, and they belong on many converting lines. The Dropometer is the right tool when you need the number behind the pass or fail: contact angle, surface free energy and its parts, on any surface, with a saved record. Book a 15 minute demo and bring a treated and an untreated sample.
Frequently asked questions
How do you use dyne pens?
Draw a line of ink across the surface. If the ink stays as a continuous film, the surface's dyne level is at least the pen's value; if it pulls into beads, it is lower. Test with higher or lower pens to bracket the level.
Are dyne pens accurate?
They give a band, usually in 2 dyn/cm steps, read by eye. Fresh pens on clean film work well for pass or fail checks; ink ages within about six months, and some pen designs can carry contamination between tests (ACCU DYNE TEST says its valve tip guards against this).
What is the difference between dyne pens and dyne test inks?
Pens hold the test liquid in a marker. Test inks are bottled fluids. ACCU DYNE TEST sells standard levels in 2 dyn/cm steps and every level from 30 to 72 in 1 dyn/cm steps.
Which standards cover dyne testing?
ASTM D2578-23 for polyethylene and polypropylene film, and ISO 8296 for plastic film and sheeting.
Can the Dropometer replace dyne pens?
It can replace them where you need a number or a record, or where the surface is not polymer film. For a quick pass or fail on treated film, many plants keep the pens and use the Dropometer to set the limit.
Other instrument comparisons
How the Dropometer compares with other surface energy tools and contact angle goniometers.
Dropometer vs Ossila Contact Angle Goniometer
Entry benchtop, about US$3,000
DIY ImageJ vs Dropometer
Free software plus a rig you build
Dropometer vs KRÜSS DSA100 and DSA25
Premium benchtop, quote only
Dropometer vs DataPhysics OCA series
Premium benchtop, quote only
Dropometer vs Biolin Scientific Attension Theta
Premium optical tensiometer, quote only
Dropometer vs ramé-hart goniometers
Benchtop range with published prices
Dropometer vs Brighton Science Surface Analyst
Handheld water contact angle for production
All contact angle goniometer buying guides
Best instrument by budget and use case
Validated measurement approach
Where the Dropometer's accuracy figure comes from.
Benchmarked against a KRÜSS DSA100E
Dropometer contact angle and pendant drop surface tension were compared with a KRÜSS DSA100E in two peer reviewed papers: Review of Scientific Instruments (2018) and Colloids and Surfaces A (2017).
Used in 52 customer publications
Customers have cited the Dropometer in 52 peer reviewed papers, theses and conference papers, listed with links.
References
1.
ACCU DYNE TEST: Marker pens
Prices, dyn/cm steps and six month shelf life, checked 23 October 2026.
2.
ACCU DYNE TEST: Test fluids
Fluid range and composition.
3.
ACCU DYNE TEST: Safety data sheet for marker pens
Formamide and 2-ethoxyethanol; reproductive toxicity warning.
4.
ASTM D2578-23: Wetting Tension of Polyethylene and Polypropylene Films
Scope: polyethylene and polypropylene film.
5.
ISO 8296:2003: Plastics, film and sheeting, determination of wetting tension
Scope: plastic film and sheeting.
6.
Dyne Testing: Dyne pens to ISO 8296
Pen range and steps.
7.
Chen, Muros-Cobos and Amirfazli (2018). Contact angle measurement with a smartphone. Review of Scientific Instruments 89, 035117
Peer reviewed validation of the Dropometer's contact angle method against a KRÜSS DSA100E.
8.
Droplet Lab: Dropometer technical specification
Dropometer price, ranges, accuracy, add-ons and export formats, checked 23 October 2026.