What Does Hiding Power (HP) Mean?
Hiding power is the ability to hide the surface of an object. When applied too thin, a coating lacks sufficient hiding power. The hiding power of paint measures its ability to obscure a background of contrasting color.
Hiding power is also known as opacity and contrast ratio.
Opacity is a film property, whereas hiding power is a property of the whole paint. Hiding is a more general term used frequently to refer to either opacity or hiding power.
Corrosionpedia Explains Hiding Power (HP)
Hiding power is the property of a coating which enables it to hide the surface over which it is applied. The hiding power is directly linked to the film application method and the film thickness.
Because white pigments scatter incident visible light at all wavelengths while colored pigments absorb incident visible light at characteristic wavelengths, a good dispersion of pigments in the binder media strongly influences the hiding power of a coating.
In a coating with strong hiding power, the pigment particles scatter the light so strongly that it hardly reaches the substrate. If residual light is reflected from the substrate, it is so strongly scattered that it does not reach the eye. For a coating to scatter the light optimally, an even, fine distribution of the pigment stabilized by dispersing additives is essential.
Low hiding power in a coating can be caused by:
- Inefficient deagglomeration
- Pigment flocculation
The main characteristics that influence hiding power are:
- High refractive index
- Optimized particle size
There are a number of test methods available, but the most familiar is the use of hiding power charts to measure hiding power of paints. These are colored cards to which paint is applied and an assessment is made of the extent to which the color pattern is obliterated.