---
title: Surface Tension, Surface Energy, and Wettability in Flexo Printing
description: To produce a successful print, the components of the flexographic inking system must have appropriate surface tensions and energies.
---

[Information About Flexographic Printing ](https://blog.luminite.com/blog)

# [Surface Tension, Surface Energy, and Wettability in Flexo Printing](https://blog.luminite.com/blog/flexo-surface-tension-surface-energy-and-wettability)

 Written by [Luminite](https://blog.luminite.com/blog/author/luminite) | Nov 15, 2021 2:47:00 PM

The first step in obtaining good adhesion and print quality is to assure that the ink wets out on the substrate fully and evenly.

## How Flexo Surface Tension and Surface Energy Affect Wettability 

The proper wetting of the substrate is largely governed by two factors:

1. Surface tension of the ink
2. Surface energy of the substrate

### What is Flexo Surface Tension?

**Surface tension** is the tendency of liquids in contact with air to act as if they are surrounded by an elastic membrane under tension.  This force is what causes droplets to form into a spherical shape, and also prevents small particles from sinking into liquids, such as water, even if they're heavy enough.  

Surface tension arises due to the tenancy for molecules of a [liquid to stick together more strongly](https://blog.luminite.com/blog/better-ink-bonding-surface-tension) than they stick to air.  

Surface tension is expressed in[** dynes/cm**](https://blog.luminite.com/blog/better-ink-bonding-surface-tension).

### What is Flexo Surface Energy?

**Surface energy** is a very similar concept that applies to solids and refers to the excess energy at the surface of a material compared to its bulk.

Surface energy is in **joules/sq. meter**.

### Effect on Wettability  

In flexo printing, surface tension and surface energy affect *wettability*.

If you have a liquid with *high* surface tension, it tends to **bead up** and not *wet* the surfaces it comes in contact with.

If you have a surface with *low* surface energy, it will have the same effect. This is not generally the ink substrate interaction that you want.

Experiencing a flexo defect that you can't pinpoint? Check out our free printing defects guide below to help identify your problem and get your print operations back in full swing: 

### Flexo Printing Surface Tension and Surface Energy

To produce a successful print, the components of the flexographic inking system must have appropriate surface tensions and energies.  More specifically the ink needs to have a* low enough* surface tension compared to the image carrier so it will adhere to it.  The substrate must then have a *higher* surface energy to fully pull the ink off the image carrier.

In general, as the ink moves through the inking system, the surface tension/energy of each successive component** must increase**.

### Measurement of  Flexo Surface Tension and Energy

There are a variety of ways [surface tension and energy can be measured ](https://blog.luminite.com/blog/surface-tension-test-ink)due to different test conditions and materials.  

In flexography typically measurement is done using a method called goniometry.  This entails measuring the contact angle formed between a surface, and a droplet of liquid placed on it.  Surface tension can then be calculated from this measurement.

***Editor's Note:** This blog post was originally published in April 2017 and was updated in November 2021 to reflect updated insight and resources.*

[View full post](https://blog.luminite.com/blog/flexo-surface-tension-surface-energy-and-wettability)

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