Frequently Asked Questions

Wettability is the ability for a liquid to spread over a surface. Surface tension relates to liquids and specifically to the forces that are exerted onto the liquid’s surface – in balance with the external environment. The surface energy relates to solids – for which atomic motion capacity is limited. Wettability tension is used in applicable standards to describe the magnitude as actually measured when performing an ink test. It is assumed that this magnitude equals the solid’s surface energy (strictly speaking, this is an inaccurate assumption but remains a very good approximation).

SmartDrop inks are made of a subtle yet strict proportion of various liquids, defining their inner values. Once you open a bottle or start using a pen, those liquids gradually and naturally evaporate in a various degree – thus slightly altering the ink’s proper characteristics, hence modifying the tests results. Although AcXys Technologies’ unique added value focuses on a strict manufacturing process that guarantees the inks stability and results accuracy, we strongly recommend to recap the bottles and pens rapidly upon performing the tests. Furthermore, please be reminded that maximal shelf life of test inks does not exceed 3 months for SmartDrop-E and 6 months for SmartDrop-F after openning the bootle or the pen.

Making contact between an ink test and a polluted surface may result in a variation of the ink’s values, due to the surface pollution dissolving and thus contaminating the ink. This may happen when using an ink pen or the brush (on the bottle cap). The safest way to avoid ink contamination is to use ink from a bottle, and apply ink drops onto a disposable cotton bud before testing the surface.

Well, we made sure that SmartDrop-F inks can cover the widest possible spectrum of materials.

On the other hand, SmartDrop-E inks are recommended on the following materials: PTFE, EPDM, PET, PVC, but cannot and shall not be used on PP, PE, silicon, glass, aluminium, PC, PS or PMMA.

It is recommended to use different test ink types with increasing surface tensions (24 to 72mN/m). Then apply some drops onto the surface using a brush, a cotton bud or the ink pen. If the ink “wets” the surface for at least 2 seconds (i.e. ink spreads over the material surface), the material surface energy is higher than the ink surface tension. In case the ink “unwets” (the drop shrinks within 2 seconds upon application), the material surface energy is lower than the ink surface tension. The material surface energy matches the lowest ink value that can wet the material surface.

SmartDrop-E inks are manufactured in compliance with ASTM D2578-09 and SmartDrop-F inks are manufactured respecting the ISO 8296 : 2003 applicable standard.

SmartDrop-E inks are made using water, ethanol and colouring compounds - they are not toxic. However, ethanol is a flammable compound and the ink container will be labelled accordingly.

SmartDrop-F inks contain water, 2-ethoxyethanol, formamide and colouring compounds. Those ingredients are classified as toxic.

Therefore it is highly recommended to read and follow the use instructions for a hazard free experience.

SmartDrop test inks are manufactured in France by AcXys Technologies. We are a renowned expert in plasma surface treatment.

AcXys Technologies devoted time and resources to the development of SmartDrop test inks and teamed up with a lab in the Grenoble area to successfully achieve this project. It included a comprehensive systematic study that guarantees the inks stability and enables us to accurately replicate their manufacturing, risk free. We strongly commit in our products high and reliable quality, from manufacturing to packaging.

When purchasing your test inks from this website, you entrust your tests and measurements to specialists: we guarantee SmartDrop will provide trustworthy test results, without a blink.

The first question is about the material you are performing tests on. The basic data about your raw material surface energy can be easily found on the Internet. This data will guide you to pick a couple of inks with values approaching your material value. For example, if you are working on PP material, the basic energy is approx. 30 to 32mN/m. You may choose inks with values of 30, 32 and 34mN/m.
The second question is to know the values you wish to attain. This information should be mentioned in your client’s technical specifications, or can be found from your paint or adhesive supplier.

Our best option, in case you have no idea of the input and output values is to purchase a kit of 7 test inks with a large panel of values.

Ink typeSmartDrop-ESmartDrop-F
Applicable standard ASTM D2578-09 ISO 8296 : 2003
Contains Water, ethanol, colouring Water, 2-ethoxyethanol, formamide, colouring
Toxicity Non toxic Toxic
Applicable to PTFE, EPDM, PET and PVC All materials
Colours Yellow Blue
Values 22 to 72 mN/m 28 to 72 mN/m

Physics and common use provide guidelines: millinewton per meter (mN/m) measure wettability tension whereas surface energy is measured with millijoules per square meter (mJ/m²). Physically speaking, those measures are equivalent, this is why both can be found. You may also come across measures in dyn/cm²: they are another equivalent, although they differ from the SI base unit.

The pen tip for test ink pens is 5mm large.

We will place your ink pen in a zipped plastic bag, then slip it into a padded bubble envelope before mailing it to you. If you ordered a bottle, we will place it into an individual cardboard box, then slip it into a padded bubble envelope, ensuring a safe journey to you – et voilà.

Make sure you promptly recap the pens and bottles after performing your test to minimize liquids evaporations. Store your test ink in a dry, temperate room, away from sunlight. Should you not need to use your products right after receiving them, place them into a sealed plastic bag and store them in a cool place (a fridge).

At first, it is important to distinguish between the precision of the measure made with the inks – and the values of the inks. Measuring with inks allows a degree of precision of 2 to 4 mN/m. Therefore, it is commonly admitted that the measuring scales graduate 2 by 2. However, at AcXys Technologies, our degree of precision when manufacturing test inks reaches ± 1 mN/m, making it impossible that two test inks with different values obtain the same measuring result.

The applicable ISO 8296 : 2003 standard defines mixtures and compounds for the following values : 64, 65, 67 and 70 m N/m. All these values are even except for 67 mN/m, the perfect equidistance between our two extreme even values of 64 and 70 mN/m.

The actual water surface tension, when reaching 20°C, is 72.8 mN/m. However, it is customary to consider that water wettability is 72 mN/m. This is the value we retained for our inks as they contain 100% pure water.