Over a period of time, some materials such as ink, paint, plastics, fabrics will fade and degrade when exposed to natural light. Why is this? On this occasion the source of the problem is Ultraviolet (UV) radiation emitted by the Sun situated 93 million miles away.

Physics and Chemistry

So, with the help of some basic physics, the Sun emits many different kinds of electromagnetic radiation. Ninety-nine percent of the light we receive from the Sun contains three types of energy:

  • Visible light, the portion of the electromagnetic spectrum that is visible to the human eye and allows us to see.
  • Infrared radiation – when exposed to infrared rays, the molecules of a substance vibrate back and forth, creating heat and warmth.
  • Ultraviolet radiation – the energy contained in ultraviolet rays is higher, so instead of just causing the molecules to shake, it actually can shake electrons away from atoms, or cause molecules to split. This results in a change in the chemical structure of the molecule.

Why does UV light cause colour to fade?

Colour fading is the result of a chemical process known as photodegradation produced by exposure to ultraviolet radiation. All colours and dyes contain light absorbing colour bodies known as chromophores.The colours that we see are based on the chemical bonds of chromophores and the amount of light that is absorbed in a particular wavelength. Exposure to ultraviolet rays will slowly break down the chemical bonds and result in the fading of colour in the inks/dyes/print on the surface of an object. In this instance colour fading is a bleaching effect. Some objects are more prone to fading, such as water colours and dyed textiles.

How can fading be prevented?

Outdoor environments will produce high levels of UV light/exposure. To ensure the longevity and durability of signage, labels and overlays used in outdoor environments, UV resistant inks can be applied. These inks are suitable for use on a variety of materials such as thin-film plastics, metals, and textiles and will aid long-lasting, vibrant colours. Reflective surface finishes and UV filters will also help to lessen the impact of ultraviolet exposure.

(Ultraviolet rays also weakens and makes plastic brittle. Many polymers are used in plastics, nylon and polystyrene, these polymers lose strength and are broken down when exposed to UV light).

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For advice or to find out more about UV resistant inks, call us on 01473 820060 or email sales@ching.co.uk