Now that you have learned what opacity & hiding power are, let us walk through the test methods used to determine the opacity of paints and coatings. Hiding power is also known as opacity and contrast ratio. Opacity is a film property while hiding power is a property of the whole coating. On the other hand, hiding power is the ability to hide the surface of an object. It quantifies how effectively paint covers the surface. Opacity is one of the crucial characteristics while determining the quality of paint. Typical binders have a refractive index of 1.49. It is the most widely used white pigment to impart opacity and whiteness to paints and coatings. For example, titanium dioxide has a very high refractive index of 2.7 (Rutile) and 2.55 (Anatase). The pigment diffuses/reflects light before it can reach the underlying substrate making the coating film appear opaque and vibrant. The higher the refractive index of the pigment, the higher opacity it delivers to a coating. When a coating is opaque the pigment particles present in a coating scatter and/or absorb light sufficiently to prevent it from reaching the substrate. The refractive index is a measure of the ability of the material to refract or bend light as it passes through the material. Opacity is a material’s optical property related to the refractive index (n). Key Optical Properties – Opacity, Hiding Power and Refractive Index Let us first begin by understanding opacity in general. We will discuss how these factors determine the opacity of coatings and how to obtain the desired opacity in your formulation. and parameters, such as pigment dispersion, film thickness, etc. Opacity is a simple phenomenon that results from the complex interplay of various components pigments, extenders, dispersants, mineral fillers, etc. Given the same thickness of applied coating film, not all coatings have the same opacity. This ability of a coating film to completely mask the underlying substrate is determined by the opacity of the coating. black, that completely hide most substrates in a single coat, while yellows or reds may take multiple coats to get full coverage. When a paint or coating is applied onto the substrate, the first and foremost requirement is “ how effectively a coating hides the substrate?”. Masking the Substrate to Determine Opacity What are the Factors That Influence the Opacity of Coatings?.Ingredients & Opacifiers – Get the Right Opacity in Your Coating Formulations.Popular Methods to Measure the Opacity and Hiding Power.Key Optical Properties – Opacity, Hiding Power and Refractive Index.Masking the Substrate to Determine Opacity.
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