Agglomerate marbles are made of a combination of marble chips and a polyester resin. Polyester resins are very sensitive to ultraviolet light(UV) and therefore should not be used outdoors. To answer your question, yes, the marble will fade in a very short time. An application of a UV resistance coating will prolong the fading but will eventually fade again. Agglomerate marbles should never be used on exteriors.
TIP Agglomerate marbles will typically have an uneven shine across its surface. The polyester matrix will fade first turning a milky color.
Article ID: 487
Created: January 20, 2022
Last Updated: January 20, 2022
Author: Pam Freitag
Online URL: https://sr-manual.com/kb/article/i-have-to-restore-an-outdoor-sign-that-is-made-of-a-black-agglomerate-marble-the-sign-is-faded-and-is-very-gray-i-performed-a-small-test-patch-and-i-was-successful-at-restoring-the-sign-the-question-i-have-is-what-caused-the-agglomerate-to-fade-a-487.html