Natural stones have been a cornerstone of both ancient and modern architecture, celebrated for their durability, aesthetic appeal, and historical significance. From magnificent temples to modern luxury homes, stones like granite, marble, sandstone, and limestone have left their mark on human civilization. However, preserving natural stones is crucial to maintain their beauty and strength, as exposure to environmental and human factors can lead to their deterioration.
In this blog, we’ll explore effective methods to protect natural stones and prevent damage, ensuring they remain timeless for generations to come.
Importance of Preserving Natural Stones
The preservation of stones goes beyond aesthetics. It safeguards structural integrity, reduces maintenance costs, and prevents costly replacements. Although preservatives can only slow down the natural decay process and cannot entirely prevent it, they play a significant role in extending the life and appearance of stones.
Preservation is essential for:
- Protecting Historical and Cultural Monuments: Ancient structures like forts and temples rely on preservation to endure environmental challenges.
- Enhancing Durability: Preserving stones protects them from freeze-thaw damage, salt crystallization, and chemical attacks.
- Maintaining Architectural Beauty: Proper treatment prevents discoloration, spalling, and biological growth, keeping the stone’s natural appeal intact.
Methods to Protect Natural Stones
1. Temporary Protection Techniques
For short-term protection, simple methods like coating the stone with paraffin, boiled linseed oil, or light paint can prevent damage. However, these methods are not permanent and require frequent reapplication.
Before applying linseed oil, it should be boiled and applied in three coats. A subsequent layer of diluted ammonia in warm water can further enhance protection.
2. Szerelmy’s Liquid Treatment
This method involves washing the stones with a thin solution of silicate of soda or potash, followed by an application of calcium chloride (CaCl₂). Together, these solutions form silicate of lime, which seals the pores of the stone and creates a protective insoluble film. This process not only strengthens the stone but also safeguards it from environmental damage.
3. Water-Repellent Treatments for Freeze-Thaw Damage
Freeze-thaw cycles can severely damage porous stones. Water entering the pores expands when frozen, causing the stone to crack and spall.
To counter this, stones can be treated with water repellents like ProSoCo H40 and H100, which deposit silica into the pores and increase the stone’s strength. It is important to avoid using low-porosity stones in freeze-prone areas, as they are less resistant to such damage.
4. Cleaning Natural Stones
Post-installation cleaning is vital for preserving the appearance and health of stones. While muriatic acid diluted with water is commonly used, it is unsuitable for stones like limestone and marble, as acid can discolor them. Instead, use safer alternatives like ProSoCo’s Safety Klean for such delicate stones.
5. Chemical Surface Treatments
While chemicals like lead paint and coal tar were traditionally used as stone preservatives, they are now considered outdated due to their adverse effects on the stone’s natural appearance.
Modern alternatives include color enhancers, which deepen the stone’s natural color and provide water and stain repellency. These enhancers maintain the architectural value while protecting the surface.
6. Preservation with Baryta in Industrial Areas
In industrial towns, stones often face sulphate attacks due to sulfur dioxide in the air. This reacts with calcium in the stones, forming calcium sulfate, which eventually flakes off and exposes fresh stone surfaces to further attack.
Baryta (Ba(OH)₂) is used to counter this damage. It reacts with calcium sulfate to form insoluble barium sulfate and calcium hydroxide. The calcium hydroxide then absorbs carbon dioxide from the air, forming a protective layer of calcium carbonate.
This chemical reaction effectively protects industrial buildings and monuments from sulphate damage.
7. Protecting Against Salt Damage
Salt damage is common in porous stones exposed to salty water. When salt crystallizes within the stone’s pores, it causes discoloration, spalling, and surface damage.
To prevent this, apply ProSoCo Salt Guard, a water-repellent solution that protects stones from salt penetration. Additionally, ensure proper drainage and soil moisture control to minimize salt damage.
Best Practices for Stone Preservation
- Use Mild Cleaners: Avoid harsh chemicals that can corrode or discolor the stone.
- Seal Regularly: Apply appropriate sealants and reapply them periodically to maintain protection.
- Inspect Frequently: Regularly check for signs of cracks, discoloration, or spalling and address issues promptly.
- Avoid Acidic Substances: Keep vinegar, lemon, and other acidic cleaners away from stone surfaces.
- Minimize Environmental Exposure: Use shade, awnings, or protective coatings to shield stones from extreme weather conditions.
IS codes Considerations for Stones
In India, the Bureau of Indian Standards (BIS) provides guidelines and specifications for natural stones, covering various aspects like testing, usage, preservation, and durability. Below are the relevant IS codes for natural stones:
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General Specifications and Classification
- IS 112:1974 – Methods of Identification of Natural Building Stones
- Covers guidelines for identifying different types of natural stones.
- IS 3622:1977 – Specifications for Sandstone
- Provides specifications for the physical and chemical properties of sandstone.
- IS 3316:1974 – Specifications for Granite
- Covers physical and chemical requirements for granite used in construction.
- IS 1124:1974 – Method of Determination of Water Absorption
- Describes testing methods to measure water absorption in natural stones.
- IS 1125:1974 – Method of Determination of Specific Gravity
- Specifies how to calculate the specific gravity of natural building stones.
- IS 1130:1969 – Marble (Blocks, Slabs, and Tiles)
- Provides specifications for marble used in building works.
Testing and Durability
- IS 1121 (Part 1-4):1974 – Methods of Test for Determination of Strength Properties of Natural Building Stones
- Part 1: Compressive Strength
- Part 2: Transverse Strength
- Part 3: Tensile Strength
- Part 4: Shear Strength
- IS 1217:1977 – Specifications for Quartzite
- Provides requirements for quartzite as a building material.
- IS 1805:1973 – Glossary of Terms Relating to Stones
- Defines key terms and nomenclature for the stone industry.
Stone Preservation and Maintenance
- IS 7779 (Part 1-2):1979 – Schedule for Properties and Availability of Stones for Construction Purposes
- Part 1: General Stones
- Part 2: Stones for Flooring
- IS 1122:1974 – Method of Test for Determination of True Specific Gravity of Natural Building Stones
- Focuses on identifying density and quality parameters of stones.
Paving and Finishing Stones
- IS 1237:2012 – Cement Concrete Flooring Tiles
- Though focused on tiles, it has provisions for stone tiles in flooring.
- IS 14223 (Part 1 & 2):1995 – Polished Building Stones
- Provides specifications for polished granite slabs and tiles.
Salt Attack and Weathering
- IS 2106:1980 – Methods for Determination of Weathering of Stones
- Specifies techniques to measure weathering effects on natural stones.
- IS 2386 (Part 1-8):1963 – Methods of Test for Aggregates for Concrete
- Though primarily for aggregates, it includes tests relevant to stone durability.
These codes ensure the proper selection, testing, and preservation of natural stones for various construction purposes in India. For detailed standards, you can refer to the Bureau of Indian Standards (BIS). Let me know if you’d like to dive deeper into any specific code!
Conclusion🎯
Natural stones are a timeless investment, cherished for their elegance and durability. Whether part of ancient heritage monuments or modern architectural marvels, these stones require thoughtful preservation to withstand environmental challenges.From simple temporary measures to advanced treatments like Szerelmy’s liquid and baryta, various methods can be used to protect and prolong the life of stones.