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An opacifier is a substance added to a material in order to make the ensuing system opaque. An example of a chemical opacifier is tin dioxide (SnO2), which is used to opacify ceramic glazes.[1]

Opacifiers must have a refractive index (RI) substantially different from the system. Conversely, clarity may be achieved in a system by choosing components with very similar refractive indices.[2]

Opacifiers must also form small particles in the system. Opacifiers are generally inert.

Sometimes opacifiers are added to medical implants to make them visible under X-ray imaging. This is especially true in the case of most polymers which are often unrecognizable in the body when viewed using X-rays.

In solid (composite) rocket motors, the primary method of heat transfer into the propellant grain from the combustion process is by radiation, and opacifiers such as "lamp black" may be added to the propellant mixture to ensure the heat does not penetrate far below the surface of the grain, which could cause detonation.


  1. Tin Oxide ( SnO2 ) Stannic Oxide – Properties and Applications, The A to Z of Materials.
  2. Raghavan, V. (2004). Materials Science and Engineering: A First Course. India: Prentice Hall. ISBN 8120324552.