TS EN ISO 19403-1

TS EN ISO 19403-1 defines the core terminology and general principles used to describe wettability in paints and varnishes. Rather than prescribing a single test procedure, this part sets out the conceptual basis for the ISO 19403 series, where contact angle, surface energy and surface tension are the key quantities.

The technical framework behind wettability

Wettability is the tendency of a liquid to spread on, and interact with, a solid surface. In coating technology, that behaviour affects surface preparation, adhesion, film uniformity and the appearance of defects. In general technical terms, contact angle describes the geometric relationship between a liquid drop and the surface, while surface energy expresses how readily the solid surface interacts with a liquid. Polar and dispersive fractions are used to separate different physical contributions to that interaction.

What this part contributes to the series

• Brings together the terms and definitions used throughout the series.
• Frames the general principles behind wettability measurements.
• Provides a common technical language for comparison and communication.
• Supports the interpretation of the optical methods defined in later parts.

This first part of the series also sets the vocabulary used for characterising substrates, coatings and coating materials. It further includes the general principle of checking the measuring arrangement with reference materials. The note on non-Newtonian rheology indicates that applicability may be limited for certain liquids whose flow behaviour can make optical evaluation less straightforward.

In practice, TS EN ISO 19403-1 is most useful as a terminological and conceptual foundation for anyone who needs to interpret wettability data consistently, compare results across methods, or understand the relationships between the quantities used in the rest of the ISO 19403 series.