Paints are known for their optical characteristics, which include opacity, glossness, and Color. Opacity, in particular, is closely linked to a paint's ability to cover or hide what's beneath it.

Hiding power depends on two key factors: 1. Light scattering and 2. Absorption of light.

When it comes to white paint, its hiding power is primarily a result of strong light scattering. On the other hand, black paint's hiding power is achieved by effectively absorbing light.

In this discussion, we'll focus on white paint since it's a fundamental component of most paint colors. The variation in the refractive indices of pigments, extenders/fillers, and binders leads to the scattering of light.

You can find answers to various questions related to hiding power:

1. What is Hiding Power in Paint?

Hiding power refers to a paint's ability to cover a surface effectively, concealing what's underneath.

2. How Does Hiding Power Work?

Hiding power operates through a combination of light scattering and light absorption, depending on the color of the paint.

What is Hiding Power in Paint?

The hiding power of paint refers to its ability to cover and conceal various substrates, whether they are black, white, or already painted. It's essentially an optical property of the paint that determines how well it can hide what's underneath.

How does the rheology influence the hiding powder in paint?

The rheology of paint, or how it flows and behaves, also plays a role in hiding power. Even if two paints have the same opacity, their hiding power may differ due to their rheological characteristics. In simple terms, paints with different rheology can show varying hiding power because they behave differently when applied, affecting the thickness of the paint film. Paints with higher shear viscosity, which is a measure of how thick the paint is, may exhibit better hiding power because they create a thicker coating.

How does the Opacity influence the hiding powder in paint?

Opacity, which is a crucial factor in hiding power, is the measure of how well a paint can block light. It's defined as the ratio of light reflectance over a dark surface to light reflectance over a white surface. In other words, it indicates how effectively the paint can obscure what's beneath it. This ratio, known as the contrast ratio, is often determined using a light spectrophotometer.

Opacity = Rb/Rw x 100 (where Rb/Rw is the Contrast Ratio)

To evaluate hiding power accurately, you need to compare the paint's opacity with that of a standard or benchmark paint, assuming they are applied at the same rate. This step is vital in understanding how well a paint film or coating can hide underlying surfaces.

How Does Hiding Power Work?

Light scattering occurs at the following interfaces:

1. the pigment particles and resin

2. the pigment particles and air

The more the difference in refractive index for materials at above interfaces, the more the light bounces around.

For example, air has a refractive index number(its number is 1.0), most resins bounces more (around 1.5-1.6), and fillers bounce a lot (about 1.55-1.65).

The index of refraction of Different Pigments

When air and fillers have a big gap in the index of refraction, it will generates enough light scattering to cause hiding power.

Hiding Power of Different Pigments

Resins and extenders are in the same indices of refraction. So the extender is transparent in resins. Resin and TiO2 have a big difference in indices of refraction, which brings excellent hiding power. That's why people like using TiO2 as a kind of white hiding pigment.