The Harmful Effects of the Crystallization Process on Natural Stone

                                              The Harmful Effects of the Crystallization Process on Natural Stone

                                                                                               By: John Lanzafame

            Congratulations.  By deciding on the use of natural stone, marble, limestone, or granite, you have made a wise investment in your building or home.  Natural stone will enhance the beauty of your building or home and increase its market value.  Your investment maybe in the form of a new installation or the restoration of in-place stone or terrazzo.  Natural stone is a highly sustainable and extremely durable material that requires minimal maintenance.  However, stone, especially marble and limestone, tends to dull over time.  It will lose its luster, become scratched, chipped, or stained.  One of the many positive characteristics of natural stone is its ability to maintain its beauty through proper maintenance.  It is this characteristic that enables the building owner to maximize the return on investment over the long term.  The key is to select the correct maintenance process.

            There are two processes that can be used to maintain natural stone and terrazzo, a natural procedure that uses a series of diamond abrasives and a crystallization procedure also known as re-crystallization or vitrification, that uses chemicals.  To ensure the maximum return on your investment while enjoying ecological benefits as well, the natural polish procedure is superior to the chemical crystallization procedure.

            To fully understand the negatives of the chemical crystallization process and the harm it will cause to your stone, one must first examine the physical make-up of the stone.  There are two categories of natural decorative stone: calcite based stones (Marble, limestone, terrazzo which is 60% marble at its surface) and quartzite based stones (granite).  The process of chemical crystallization is promoted as an inexpensive means to maintain a lasting shine to calcite based stones.  What is not disclosed in this promotion is the harmful effect the chemicals will have on the stone.

            Chemical crystallization is the process of chemically transforming a thin layer of calcium carbonate (Calcite) at the stone’s surface into calcium fluoride.  A solution of fluorosilicate compounds and waxes are buffed into the stone so that the acid will breakdown the calcite.[1]  In very simple terms, a chemical reaction takes place, combining with the wax to produce a shine on the surface of the stone.  This chemical process alters the composition of the stone causing a physical degradation and yields a plastic “waxy” appearance.  Chemical crystallization can destroy your investment in several ways physically, aesthetically, and lead to increased maintenance and replacement costs over the long term.

            For natural stone to be classified as geological marble, it must contain at least 60% calcite.  The remaining 40% can be composed of other natural minerals.[2]  It is this variation in composition that imparts a variety in the appearance of the marble.  The variation in composition also produces different chemical reactions when subjected to the chemical crystallization process.  Applying the chemical crystallization process to white marbles runs the risk of causing discoloration such as a yellowing.[3]  The crystalization process may also cause stone to become brittle at the surface and crack under minimal pressure, i.e. a woman walking over the stone in high heals.  Over time, a chemically crystallized stone floor will assume a waxy plastic finish.[4]  With each additional chemical application, the objective of achieving the original luster becomes more and more difficult to achieve.  Quarterly maintenance schedules become monthly maintenance schedules, increasing the costs and expediting the physical deterioration of the stone.  Also, the chemical solutions used in the crystallization process are not universal.  Therefore, if one elects to crystallize their stone they are forever stuck with the process and the vendor who applies it, or they must go through a full restoration which includes grinding or costly replacement.

            The natural polishing process has advantages over the chemical crystallization process.  They include a greener, chemical free process which helps to increase the sustainability of your stone.  In many cases, a proper natural polish has a more enhanced aesthetic appeal than a factory finish.  The process is universal, and will become easier over time.

            In conclusion, the process of chemical crystallization also known as re-crystallization or vitrification, is promoted as an inexpensive method for maintaining natural stone and terrazzo.  However, over time, this process degrades the structure and appearance of the stone, leading to increased maintenance costs or even expensive replacement.  A natural polish procedure is a superior means of maintaining natural stone and terrazzo.  Over time, your investment in the stone is minimized, increasing the rate of return in your building.