When implementing various projects, parameters such as colour or gloss are very often defined. They do not affect the durability of the coating but have a visual effect on the target customer and allow the product to be properly adapted to his taste and requirements. In addition, industrial companies producing products, structures have many branches or use the services of sub-suppliers, which significantly hinders the production of two copies of the same, uniform colour. Measurements of visual parameters are also conducted after exposure of the samples to aggressive conditions causing degradation of the coating and causing visual changes on the surfaces of the products, i.e., discoloration, fading, yellowing, loss of gloss. Measurements of the change in colour and gloss will allow the estimation and direction of changes in the appearance of the coating during accelerated aging exposure. Thanks to this, it is possible to verify durability and resistance to various conditions (moisture condensation, exposure to an aggressive environment or exposure to light). This will allow you to estimate the resistance of the products to a change in colour and gloss after a certain period of use.
The reception and perception of colour, in addition to environmental conditions, are significantly influenced by surface preparation as well as gloss. In order to standardize the definition of the colour, systems are used that allow it to be specified numerically. The CIE Lab system is the leading one. The colour is defined by 3 coordinates: L * – brightness and a * and b * defining its key. In order to produce a series of identical products, it is necessary to define a pattern to which the colour will be compared. On this basis, its difference ΔE * is calculated. The assessment can also be based on additional customer-defined criteria. The measurement performed with 45/0 geometry reflects the sensation of colour reading by human eyesight. The device uses circular illumination at an angle of 45 °, and the intensity of the reflected light is assessed over the test sample.
In our laboratory, we conduct tests with a comparative colorimeter – in accordance with PN-ISO 7724-3. The measurement is determined in the CIE lab, XYZ colour spaces, measurement geometry 45 ° / 0 or 0/45 ° or in the SCE diagram.
In addition to colour control, we also conduct gloss measurements. This parameter also significantly influences the colour perception of the observer.
The gloss test is conducted with a triangular glossmeter compliant with the PN-EN ISO 2813 standard, at an angle of 20 ° / 60 ° / 85 °. The radiation intensity of the reflected specular light directed at the test surface at an appropriate angle is measured. On the basis of the obtained results, the compliance of the gloss with the ΔG standard is assessed. An important aspect is to determine whether the tested values are within the assumed tolerance limits.