1. Lustre

Lustre is a characteristic of the surface of a material and is second only to colour in the assessment of decorative materials. When light is directed at an object, part of the light is reflected. Reflected light can be scattered in all aspects of the formation of diffuse reflection, if it is concentrated to form a parallel reflection of light is specular reflection, specular reflection is the main factor in the production of lustre. So the lustre is a directional reflection of light, it is formed on the surface of the object image of the clear degree, that is, the strength of the reflected light, plays a decisive role.

2、Transparency

The transparency of the material is also a property related to light. Objects that can transmit light and see through are called transparent; objects that can only transmit light and cannot see through are translucent; objects that cannot transmit light and cannot see through are opaque.

3. Colour

The colour of a material is determined by three factors: the spectral reflection of the material, the spectral composition of the material when viewed and the spectral sensitivity of the viewer's eye. So colour is not inherent to the material itself, it involves physics, physiology and psychology.

(i) For physics: colour is light energy.

(ii) For psychology: colour is perception.

(iii) For physiology: colour is sensed by the nerves of the eye and the cells of the brain*.

A person's psychological state reflects his or her perception of colour, and generally people react strongly to incongruous colour combinations. Colour is therefore extremely important for decorative materials. People cannot distinguish the same colour exactly, so a spectrophotometer should be used to objectively and scientifically determine the colour.