03.04.2025

Masterbatch Know-how: Weather- and Light Fastness

The intended use is important for the development of these masterbatches

If you have an application that needs to be suitable for outdoor use or needs to be protected from UV radiation, you need to consider what is known as weather and light fastness. Do you want to achieve a long service life and high quality for your products and colours? Then we should know that:

- Which product is to be manufactured?
- How much and how long will the product be exposed to the weather?
- Where will the product be distributed? (in humid or cool climates or in countries with special UV indices)

Our customer service requires this and other information for a laboratory order.

Important facts about light fastness

Lightfastness (or light resistance) describes the resistance of colours to prolonged exposure to light, especially sunlight with a high UV content. Chemical degradation (photooxidation) occurs: Cracking, deterioration of mechanical and physical properties as well as colour changes such as fading can be the result. There is no such thing as permanent lightfastness and the degradation process can never be stopped completely.

The higher the UV radiation, the higher the quality of the colourants

We use suitable colourants depending on the requirements: The greater the challenge, the higher the demands on the polymer and masterbatch. Our colourists know the suitability and properties of colourants inside out. Together with you, we also clarify whether filler or light stabiliser additives are relevant in a combination batch, which are also available without colour as pure additive batches (LIFOSTAB products).

Measurements with the blue wool scale

If a (new) raw material or a specific recipe is to be checked, the most common method is the wool scale, also known as the blue wool scale. This measurement is carried out manually and visually. The wool scale ranges from level 1 (=low light fastness) to level 8 (=high light fastness). The eight blue wool strips fade differently when exposed to light due to their colouring agents. The scale is placed on the sample to be tested, covering a part of the sample and the wool strips. After irradiation, the samples and the wool strip are compared: The difference found determines the lightfastness.

Don't know what light fastness your product needs? We can help you with questions and expertise to determine the right light fastness and develop the right masterbatch on this basis.

Important information on weather resistance:

Weather fastness is also of decisive importance for quality and durability. It describes the resistance of materials to external weather and environmental influences (such as temperature, UV radiation, moisture, air constituents) - in other words, it encompasses more factors than light fastness and UV radiation. Lifocolor has a weathering machine for measurements under laboratory conditions.

Weathering machine as a measuring device

The machine simulates all possible weather conditions such as heat, rain, frost, wind etc. for up to 3000 hours, customisable according to customer requirements. It complies with DIN EN ISO 4982-2, the international standard for quality testing.

A xenon arc lamp is used to measure the light resistance. In the weathering machine, moulded samples are clamped for different weathering times - if necessary with the enclosed wool scale. After weathering, the unweathered test specimens are visually compared with the weathered test specimens. The scale for assessing weather resistance generally ranges from 1 to 5 (5 = very high, 1 = very low).

Please contact us if you explicitly require a weathering test.

For further information, please contact or call our customer service on +49 9571 789-0.