Floor technicians use crystallization—also known as vitrification or re-crystallization—to create a high-gloss finish on calcium-bearing stone like marble, limestone, and travertine. The industry introduced crystallization during the 1960s. However, specialists still debate its long-term impact on natural stone.
Some contractors report excellent results without surface defects. In contrast, other stone care professionals report immediate damage or progressive surface deterioration over time. In this article, we explain how crystallization works and compare it directly to oxalic acid polishing.
Understanding Marble and Calcium-Bearing Stone
To keep things clear, we use the term “marble” for all calcium-bearing stones and cementitious terrazzo floors. These natural materials consist primarily of calcium carbonate ($CaCO_3$). In fact, this identical chemical compound forms seashells, pearls, eggshells, and common household antacid tablets.
What is crystallization:
Crystallization is a process in which a steel wool pad is used in combination with a weighted floor machine and acid solution to bring a polish to stone floors. The most common ingredients of crystallization chemicals are acid, magnesium fluorosilicate, aluminum fluorosilicate, zinc fluorosilicate, and water. Some crystallization products may also contain waxes. The chemical reaction illustrated below shows the process taking place during crystallization. Note that magnesium fluorosilicate (MgSiF6) is used in this example but most chemistries will contain a mixture of fluorosilicates. The basic reaction principals are the same no matter which fluorosilicate chemistry is used.
MgSiF6 + 2HCl + CaCO3 →CaSiF6 + MgCl2 + CO2 + H2O
Or
3CaCO3 + MgSiF6 →MgSiCO3 + 3CaF2 + CO2 + H2O
In this reaction the magnesium salts are primarily left on the surface of the stone and removed during the next cleaning of the surface, and the calcium fluorosilicate (CaSiF6) is bonded to the underlying stone and is now the layer we walk on. The surface of the stone has now been chemically altered and there is no way to reverse the process. Note that this new surface of the stone is not a coating but is now part of the stone itself.
The only way to remove a crystallized layer is through mechanical action such as diamond honing. Chemical strippers commonly used to remove acrylics will not remove crystallization. The resulting layer of calcium fluorosilicate formed on the surface of the stone is harder, more glossy, and more stain resistant than the original stone surface. This is the principal behind crystallization.
How does crystallization differ from what is done in the factory or with a polishing compound containing oxalic acid:
Most marble has been polished in the factories using various grades of abrasives followed by a final step using an abrasive in combination with oxalic acid (H2C2O4). In an effort to replicate this factory finish most marble polishes contain an abrasive to remove
fine scratches and oxalic acid to replicate the factory process. Unlike crystallization, steel wool is not required when using an oxalic acid polish. Most often, polishes are used with a red or natural floor pad under a 175rpm floor machine. Floors with deeper scratches or other damage, typically must be diamond honed prior to using marble polishing products. During marble polishing, the reaction taking place is shown below.
H2C2O4 + 2CaCO3 →CaC2O4 + CO2 + H2O
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Again, the finished floor displays a much higher gloss than the original stone. Unlike crystallization, oxalic acid leaves the natural mineral structure intact. During the final rinse, water carries the temporary calcium oxalate ($CaC_2O_4$) byproduct away in the slurry. As a result, you gain a smooth, naturally reflective surface without any permanent chemical alterations.
However, remember that oxalic acid still etches calcium-based stone if you leave it unattended. Any acidic liquid will burn marble surfaces within seconds. Therefore, restoration professionals and factory technicians always manage contact time and dilution rates strictly.
How does this difference impact the application of Scotchgard™ Stone Floor Protector?
Because crystallization permanently changes the surface, technicians must grind away the crystallized shell before sealing. Specifically, technicians use Trizact™ Diamond HX Discs to strip this layer and prepare the stone.
In contrast, oxalic acid leaves the natural pores open, so you do not need to strip any chemical layers first. Nevertheless, technicians still run Trizact™ Diamond HX Discs over the floor to erase fine scratches, level high spots, and clear surface blemishes before applying the protector.
Notice to Reader
Our team bases these technical recommendations on practical testing and hands-on field experience. However, we cannot guarantee identical outcomes for every project.
Many distinct variables influence how these chemicals perform on your floor. For instance, stone porosity, prior sealers, and room temperature all affect your final finish. Therefore, you must test every chemical product in an inconspicuous spot before completing full application.
Product Application
Every natural stone surface demands specific care. Consequently, you must evaluate the floor condition yourself to select the correct treatment method. Always follow safe handling protocols when applying any stone restoration product.
Warranty and Liability
Authorized distributors guarantee these products against manufacturing defects for 90 days from purchase. The manufacturer provides no other express or implied warranties.
If a product proves defective, the supplier will replace the item or refund your purchase price. Furthermore, applicable UK law limits liability for any consequential property loss or project damage.
Source: https://multimedia.3m.com/