Necessity
Whether it is new stone or refurbished stone, with normal use and the passage of time, wear and tear will progressively worsen, leading to a gradual loss of luster.
Timeliness
Stone materials can only achieve their intended performance through timely maintenance; if the degree of gloss loss exceeds the material’s ability to recover through maintenance, restoration to the original level will be impossible.
The correct maintenance approach is to promptly apply appropriate restoration techniques before the decline in stone gloss exceeds the capacity of the maintenance measures to restore it. Once the restoration is complete, the gloss typically returns to nearly its original level, ensuring that the stone maintains a long-lasting, like-new appearance and remains in an optimal condition for use.
Due to its naturally occurring characteristics and the fact that it is often associated with various chemical compounds, stone is inherently prone to deterioration and weathering in its environment—this is an intrinsic factor. On the other hand, adverse environmental conditions such as acid rain, pollution, and high humidity also play a major role in triggering and accelerating a wide range of problems and pathological changes in stone. The consequences of these issues can be severe. From the natural weathering and degradation of ancient stone artifacts to the diverse forms of natural damage and deterioration observed in contemporary architectural stone, the resulting losses are substantial. Consequently, developing effective preventive measures to minimize and control such damage and deterioration has become increasingly important. Waxing was once widely used as a method for protecting stone, particularly on paved stone floors. However, its protective efficacy is limited: it offers poor weather resistance, inadequate stain resistance, and tends to attract dust. Moreover, recent research has shown that waxing can even be detrimental to stone, because it acts as an impermeable sealing coating that blocks the stone’s pores, preventing internal and backside moisture from escaping. Over time, this trapped moisture can lead to internal deterioration. Another commonly applied product is liquid wax for interior wall surfaces; although it forms a film-like protective layer, its main drawback is that it compromises the stone’s natural texture. The introduction of penetrating protective treatments represents a significant advance in the development and research of stone protection products; however, their adoption in China remains relatively recent. These products typically use solvents or water as carriers to deliver effective waterproofing agents deep into the stone matrix, creating a robust protective barrier that repels water and other liquid contaminants. In addition to preserving the stone’s natural appearance and maintaining its breathability, these penetrating treatments offer superior performance and are scientifically sound. Nevertheless, due to variations in formulation, their effectiveness in waterproofing, stain resistance, and oil repellency may differ; still, most products perform well.
When selecting and using stone protection products, in addition to understanding the product’s performance, the following points should also be taken into consideration:
(1) Compatibility. Select products that have no adverse effect on the color of the stone. For wet-setting applications, when treating the back surface of the stone, verify that the treatment will not compromise the bond strength between the stone and the cement.
(2) When wet-setting installation is employed, thorough treatment of the back and side surfaces of the stone is essential; therefore, priority should be given to selecting a waterproofing agent with excellent performance.
(3) When selecting a protective agent for floor stone, in addition to ensuring effective waterproofing on the back side, the front surface of the stone must also be appropriately protected based on the specific service environment. For certain specialized settings—such as hospitals—products with excellent stain-resistant properties should be chosen; for hotels, protective products that offer superior stain and oil resistance are recommended.
(4) Protective treatment of the back surface of unitized stone curtain wall panels is now of limited significance. As for the front surface, appropriate protective products can be selected and applied based on the service environment and the specific characteristics of the stone material.
(5) For stone materials that are highly susceptible to deterioration—such as certain grayish-white granites and marbles—which often develop rust stains or yellow efflorescence under humid conditions, it is crucial to implement thorough waterproofing measures and to select protective agents with outstanding water-repellent performance.
(6) When using granites and marbles with relatively loose textures and high water absorption in public environments, it is essential to select products that offer excellent waterproofing, stain resistance, and anti-fouling performance, so that any contamination can be easily cleaned.
Common Cleaning Agents
(1) Marble Cleaner
This is an acid-free, neutral stone cleaner that is ideally suited for removing dirt, wax residues, oil stains, adhesive marks, paint, and other construction-related contaminants from marble surfaces. It does not damage the marble’s surface or its natural luster, nor does it compromise the stone’s structural integrity.
(2) Granite Cleaning Agent
This cleaning agent effectively removes dirt, dust, construction residues, adhesive stains, oil marks, and discoloration from the surface of granite, as well as from its cracks and crevices, without damaging the stone’s surface or luster.
(3) Rust Removal from Granite
This rust remover effectively eliminates rust stains and discoloration on stone surfaces caused by both internal factors and external rust contamination. It reduces metal oxides back to their original metallic form and forms a protective barrier to prevent re-oxidation and the recurrence of rust.
Color change
Stone discoloration primarily affects stone varieties with poor chemical stability. This discussion focuses on indoor applications where the stone is not exposed to ultraviolet radiation; in particular, with dry-hanging installation systems, light-colored stones tend to darken over time. A typical case is off-white travertine, where the stone cladding gradually turns yellow from top to bottom during installation and, as time passes, the entire wall surface becomes uniformly yellow. Travertine inherently has poor chemical stability: carbon dioxide, sulfur dioxide, and nitrogen oxides in the ambient air can react with the calcium oxide contained in the stone, and the resulting sulfide compounds—being white in color—inevitably cause the stone to yellow. In addition, during construction, both coatings and adhesives contain substantial volatile components, which can also react with the stone and further exacerbate the effects on stones with poor chemical stability.
Organic pollution
When stone materials are contaminated by organic substances, the affected areas darken in color and the discoloration persists over the long term, while also attracting and trapping dust. Such organic contaminants primarily originate from oil stains and contact with animals; areas that are frequently touched by human hands are especially prone to this type of pollution. In fact, the most conspicuous and intricately finished decorative stone surfaces are often those that experience the closest human contact—for example, stair handrails, which are typically adorned with custom-shaped, high-grade marble. Even less suitable is the use of Hanyang white marble sculptures as decorative elements in public spaces; the extent of contamination this material would endure in such environments is readily apparent.
Low-quality organic sealant can also cause contamination in curtain wall systems with mechanically anchored stone panels: on the one hand, it can stain the edges of the stone slabs; on the other hand, it can attract and adhere airborne dust.
Rust stains
The causes of rust stains are generally classified into two types:
The first type of rust stain originates from the iron content inherent in the stone itself. In general, all types of stone contain some degree of iron; when rainwater comes into contact with this iron, rust stains gradually form. Such stains are relatively difficult to remove and require a longer treatment period. A highly effective solution is to use KELIN KL608 Heavy-Duty Rust Remover, which boasts exceptional penetration power, allowing it to deeply infiltrate the surface pores of the stone and ensure thorough cleaning. This product can effectively eliminate rust stains without damaging the stone. It is crucial to avoid using industrial-grade hydrogen peroxide or other highly corrosive strong acids, as these can backfire and exacerbate the problem. Most importantly, to prevent the recurrence of rust stains, the most effective approach is to apply a protective treatment immediately after rust removal, thereby blocking further moisture penetration into the stone and eliminating the risk of reformation.
The second type of rust stain is external in origin, such as residual steel grit from machining or ferrous tools used during construction, as well as metal decorative elements. This kind of rust stain is relatively easy to remove and can be treated with KeLin KL308 Rust Remover. In general, once rust stains have formed on stone, completely removing them is quite difficult. Therefore, applying a protective treatment before stone installation is preferable to doing so after completion, because finished exterior walls are often at considerable heights, making on-site application challenging; moreover, during the installation process, the stone may come into contact with acid rain. Hence, pre-installation protection is the best approach, as it provides both rust and stain resistance. The phenomenon of rust stains on stone is illustrated in Figure 1.
Seepage
Due to the building’s central location, pollution levels are particularly high. Stone materials naturally possess capillary pores and are highly absorbent; over time, air pollution, dust, atmospheric acids, and exhaust emissions from motor vehicles accumulate on the stone surface. When it rains, acid rain accelerates the corrosive effects of these pollutants, which also penetrate deep into the stone’s capillaries, resulting in stubborn stains that are difficult to remove. This is especially true for flamed-finish stone, where such contamination develops more rapidly and is even harder to clean—commercial cleaning agents are simply ineffective at eliminating these deposits. Moreover, on polished stone surfaces, the original luster is quickly degraded.
Therefore, to remove such stains, a stone-specific cleaning agent can be used. These specialized cleaners are capable of completely eliminating contaminants that have penetrated the stone’s capillary pores without causing any damage to the material. To prevent future staining, once the stone has been thoroughly cleaned and its surface is completely dry, a protective treatment should be applied. This penetrating sealer penetrates deep into the stone to form an impermeable barrier that provides resistance against water, dirt, efflorescence, rust stains, oil-based stains, weathering, aging, and acidic or alkaline substances—such as tea, cola, and soy sauce—while effectively controlling the formation of white efflorescence. Importantly, this treatment does not impair the stone’s natural breathability. For routine maintenance, simply wiping the surface with water is sufficient; no additional cleaning agents are required.
Pre-emptive Protective Treatment for Exterior Wall Contamination: In general, stone cladding on exterior walls is installed at considerable heights, making post-contamination cleaning and remediation extremely inconvenient. By applying a thorough protective treatment in advance, contamination can be effectively prevented once the project is completed, allowing routine maintenance to be carried out simply by rinsing with clean water. Moreover, pre-construction protective treatments are relatively low-cost and easy to apply. The use of stone protection agents has fundamentally addressed the time-consuming and labor-intensive challenges associated with traditional protective methods, and this approach is already widely adopted in stone projects overseas.
Water stain
After stone finishes are completed, they often remain damp for a long time, with persistent wet marks on the surface—this is commonly known as water staining. The causes of water staining are complex. Some scholars attribute it to the high water absorption of the stone, inadequate stone protection, and the infiltration of atmospheric precipitation or building seepage into the stone’s interior, leading to water saturation and the subsequent formation of water stains. However, each case must be evaluated individually. For instance, in areas of buildings that are subject to prolonged water exposure—such as restrooms or utility rooms—water staining is consistent with this explanation when it results from pipe leaks or rainwater drainage systems. That said, when water staining occurs widely on wall surfaces in non-water-rich environments or on the floors of high-rise buildings, the conventional explanation falls short. In such cases, more sophisticated analytical methods are required: the composition of the water stains must be examined, their sources identified, and the root cause of their formation determined, so that targeted remediation measures can be implemented. In essence, water staining is the most common problem encountered in the stone application and maintenance industry; it is also the most complex in terms of causation, the most challenging to address, and a critical issue that will demand substantial effort to resolve in the future.
Removing water stains is notoriously difficult, as their formation is highly complex. Factors such as cement residues, acid rain, efflorescence, poor-quality aggregates, and contamination absorbed by the stone from underground all contribute to the deterioration of the stone itself. Once the stone has deteriorated, it becomes exceedingly challenging to clean thoroughly. Therefore, the only effective approach to dealing with water stains is prevention. To prevent their formation, apply a stone protective treatment before construction. By treating the stone prior to installation, you can effectively inhibit the development of water stains while also achieving excellent stain-resistant performance.
Bai Hua
Efflorescence refers to the appearance of white powder or streaking on stone surfaces or in grout joints, and it commonly occurs in outdoor settings or areas with abundant water sources, such as flower beds, outdoor steps, and exterior wall grouting.
When stone is installed using wet-setting methods, alkaline substances such as calcium hydroxide in the backfill cement-sand mortar are dissolved by large amounts of water and leached to the stone surface or into poorly filled joints. Subsequently, calcium hydroxide reacts with carbon dioxide in the air or with sulfur dioxide and other sulfate compounds in acid rain, forming calcium carbonate or calcium sulfate. As the moisture evaporates, these salts crystallize and precipitate, resulting in efflorescence.
The factors that cause efflorescence in stone are similar to those that cause water stains: abundant moisture and alkaline metal ions are both contributors to efflorescence. Moisture acts as the primary carrier, dissolving the alkaline metal ions and then driving them to the stone surface or into poorly sealed joints via capillary action, where they subsequently precipitate as efflorescence. Therefore, preventing the penetration of moisture and alkaline metal ions into the stone surface or inadequately sealed joints is the key to averting efflorescence.
The following measures can prevent efflorescence:
Prior to installation, stone materials shall be treated with a protective coating—applied to the face, five sides, or all six sides, as required by the project—to prevent excessive water absorption. This treatment also serves to inhibit water penetration through the stone’s face and to prevent groundwater from infiltrating the cement mortar beneath the stone, thereby preventing the leaching of alkaline metal ions from the mortar into the stone and the resulting efflorescence.
Select grouting materials that are suitable for stone and apply them using the correct installation procedures. High-quality grouting materials combined with proper application techniques can effectively prevent efflorescence at the grouted joints.
When preparing cement mortar, use a low water-to-cement ratio or add a water-reducing admixture. Reducing excess water can prevent the occurrence of efflorescence.
Adding a waterproofing agent to cement mortar can prevent metal ions from being leached out in large quantities by water, thereby inhibiting efflorescence on the stone surface.
Select non-polluting aggregates; for example, avoid using sea sand with high concentrations of calcium, magnesium, and sodium ions, and refrain from using groundwater rich in minerals as mixing water, thereby reducing the sources of metal ions and lowering the likelihood of efflorescence.
Measures that have already resulted in white bloom:
A specialized stone cleaning agent can be selected; KL710 descaling agent is specifically formulated to address the various whitening phenomena on tile and stone surfaces, effectively removing both natural efflorescence and calcium carbonate deposits (whitish stains) caused by improper cleaning from tiles, glazed bricks, terracotta products, natural stone, and concrete products.
Applying a stone protective treatment after cleaning can prevent the recurrence of efflorescence on stone surfaces.