Limestone is a clastic sedimentary rock formed from fragments of other rocks, fossils and grains. The stone is predominantly composed of calcite and can be various colours including white, grey and pink. The appearance and workability of Limestone allows it to be used for diverse purposes, from decorative statues to exterior facades of buildings. These qualities are why limestone has been a popular choice of material for thousands of years.
Different colors and textures of limestone
Typical Uses of Limestone
Kitchen countertops: limestone countertops are used in kitchens for their diverse range of colours and aesthetic appeal. The stone is easily worked, so nearly any style of countertop design can be built.
Showers: a shower tiled in limestone can provide a luxurious and elegant feel to a bathroom. This does not compromise the usability of wet area as the texture of the stone is pleasant under foot.
Floors: Limestone flooring, especially in bathrooms is a popular choice for its visual appeal. Polished or honed finishes are usually applied to this surface.
- Polished: The surface has a mirror gloss with sharp reflections, a popular choice for kitchen countertops and floors. Fingerprints, dust marks and staining will be more visible on polished limestone.
- Honed: A smooth dull, non- reflective sheen is left on the surface. This finish can be an attractive feature for a limestone countertop, floor or shower tile.
Patios and other outdoor areas: Limestone is used outdoors for its aesthetic qualities and ability to be cut into various shapes and sizes. This affords great flexibility when designing or installing courtyards and patios.
- Bush-hammered: The surface has a coarse, textured finish created by hammering.The micro-fissures caused by bush hammering can leave limestone surfaces more vulnerable to staining, efflorescence and spalling. This finish can also reduce the strength and durability of limestone, lowering the effective thickness.
Common Problems of Limestone:
Limestone that is located outdoors can be susceptible to a condition known as efflorescence. It is caused by water moving through the substrate of a material collecting and carrying minerals and salts found in the mortar bed, grout, soil or the stone itself. When the impure water reaches the surface of a material and evaporates, the minerals and salts will be left behind. Through a reaction with carbon dioxide in the air, these form those white marks commonly seen on unprotected porous surfaces.
If detected early, efflorescence can be removed using a metal brush. Time is essential, the longer efflorescence is left to cure the more difficult it will be to remove. However, the best treatment for efflorescence is prevention. Dry-Treat’s STAIN-PROOF Original™ provides premium water and oil repellency. The sealer deeply penetrates into the pores of a material, permanently bonding through a chemical reaction. This creates a water-repelling barrier which stops water ingress. The pores of the material are not blocked so moisture trapped in the substrate can escape as vapour, preventing the salts and minerals reaching the surface.
Although different types of Limestone may range in porosity any stain left on the surface will eventually be absorbed into the material. The type of finish on a limestone surface can also impact on the level of staining. Bush-hammered limestone is more likely to be stained than other finishes. This is because in order to give the stone that rough look pieces of the surface are removed by hammering, allowing liquids an easier path into the limestone.
Dry-Treat™ has a number of products that can protect against staining and remove those difficult deep stains.
- STAIN-PROOF™ Original provides superior water and oil repellency, which will help prevent staining from food and liquid spills on all granite surfaces. The invisible, impregnating sealer permanently bonds to the pores of granite through a chemical reaction. This means a treated surface will not be affected by traffic, exposure to UV radiation or commercial cleaning processes.
- Oxy-Klenza™, part of Dry-Treat’s HANAFINN range is perfectly suited for removing stubborn stains. The powerful, oxygen based cleaner can be made into a closed poultice which can remove stains that have had time to sink into dense stones such as granite. Refer to our maintenance guide for how to apply a closed poultice to a stain.
Salt spalling on white limestone pool coping
Limestone, like all porous materials has millions of interconnected pores which absorb water and dissolved salts and minerals. However, because limestone is a very soft, porous stone it is more likely to incur spalling. When water evaporates it leaves salt crystals behind below the surface. When these crystals grow close enough to the surface they break off microscopic pieces of the material. This allows more water ingress which accelerates the spalling over time until the limestone is visibly damaged.
In cold climates, water that has been absorbed into the pores of limestone can freeze. Frozen water can expand by up to 9 per cent. When this happens close to the surface microscopic pieces of limestone can break off. As with salt spalling, over time this can cause visibly deep damage.
To protect against salt and freeze-thaw spalling DRY-TREAT 40SK can be used. The invisible, impregnating sealer is specially designed for soft, porous materials in freeze thaw climates and salt water environments. Limestone treated with DRY-TREAT 40SK will have permanent water repellence. The protective barrier will significantly reduce water ingress and subsequent freeze-thaw and salt spalling.
There are thousands of species of fungi that can be classified as mold. Molds are highly resilient organisms which can survive in almost any environment but damp or humid areas are where it thrives. This means that mold can be grow on your natural stone indoors and outdoors. The fungi can not only ruin a limestone surface but it also has health risks. The effects of exposure can range from mild eye and skin irritation to severe lung infections.
Although mold can live in a range of climates, it cannot survive without water. Applying an impregnating sealer like STAIN-PROOF Original™ to a limestone surface can significantly reduce the amount of water absorbed, inhibiting the growth of mold, moss, mildew and other biofilms.
Picture framing can occur when grouting a paver that has not been pre-sealed. The water inside grout contains cement and other minerals. When this water penetrates into the edge of the paver, the minerals set inside the limestone. This leaves a permanent stain, identified by the distinctive dark frame seen around the edge of a material.
Picture framing can also appear over time. Grout is extremely porous which means it will absorb more water than the limestone itself. This impure water will permeate around the edge of the paver numerous times. When the surface dries, the water evaporates leaving behind minerals which are permanently set inside the limestone, making it impossible to remove.
Once picture framing has occurred there is no way to remove it, so prevention is vital. Sealing your limestone surface and surrounding grout with a Dry-Treat impregnating such as STAIN-PROOF Original provides a deep, water-repelling barrier. This will significantly reduce water being absorbed into the grout and material, lowering the risk of picture framing.
Calcareous stones such as limestone are vulnerable to damage known as acid-etching. When anything acidic such as lemon, cola, coffee or wine comes into contact with an acid-sensitive material it will dissolve the calcium inside the stone. This results in a permanent, rough, physical mark. No impregnating sealer will prevent acid-etching. This is because they do not physically stop a substance from touching the surface.
For bathrooms tiled in limestone, soaps that contain citrus additives should be avoided as they are acidic and will damage the stone. Limestone that is used outdoors may also be subject to acid-etching. Rain and bird droppings can be acidic which will discolour and damage limestone surfaces.
Protecting your limestone surfaces
For protection against stains, efflorescence and the enhancement of limestone surfaces:
STAIN-PROOF™ Plus - 2 coats
To protect natural stone countertop we recommend using STAIN-PROOF PLUS™. The impregnating sealer is specially designed for dense stone countertops. The superior depth of penetration means your surface will have permanent water and oil repellence.
Note: Dry-Treat’s impregnating sealers will not prevent acid etching because they do not physically prevent an acidic substance from touching a surface. For protection against acids Dry-Treat’s Vitremela™, the thin, 100% acid-proof, heat and scratch resistant coating can be applied to limestone countertops.
For natural look:
STAIN-PROOF™ Original - 2 coats
For protection against water and oil-based stains and efflorescence we recommend using STAIN-PROOF™ Original. The sealer’s deep penetration into the pores of your material will provide superior water and oil repellency. This will stop food and liquid spills from causing permanent staining and significantly reduce the formation of efflorescence. STAIN-PROOF™ Original creates a chemical bond inside the pores, permanently becoming part of your material.
META-CRÈME™ - 1 coat
For indoor applications, we recommend using META CRÈME™ for protection against water and oil-based stains and efflorescence. The ultra-low VOC sealer chemically bonds to the lining of a material’s pore structure, providing permanent protection. META CRÈME™ deeply penetrates into the pores which creates an excellent water and oil repelling barrier. This sealer is easier to apply, requiring only 1 coat, and is suitable for smooth surfaces.
For enhanced look
INTENSIFIA™ - 2 coats
For superior color enhancement of a surface whilst providing protection against water and oil-based stains, we recommend using INTENSIFIA™.
For surfaces in saltwater environment:
DRY-TREAT 40SK™ - Dip Seal
We recommend using DRY-TREAT 40SK™ for softer more porous stones in freeze-thaw climates and salt-water environments such as swimming pools or near the coast. This type of material is more vulnerable to water and salt ingress. DRY-TREAT 40SK™ is a permanent water repellent and consolidator. The invisible, impregnating sealer provides superior water repellency whilst strengthening your stone.
Maintaining your limestone surfaces
For everyday and heavy-duty cleaning of your limestone surfaces:
Maintenance is an important part of owning a natural stone or other hard porous surface. Being diligent about the condition of your surface can minimize the need for regular, heavy-duty cleaning. There are a few simple actions that can be taken such as:
- Wiping up spills as soon as possible.
- Regularly washing down areas such as pool surrounds with fresh water after use.
- Frequently removing leaves, branches and other plant matter from patios. If left for long enough, some leaves will bleed tannins, staining the surface.
- Using walk on/walk off mats and vacuuming can reduce the amount of grit on a surface
- Avoid spilling acidic substances such as lemon, cola, tomato sauce, or even using cleaners that contain acid as it can leave a permanent etch on the limestone surface
For outdoor cleaning:
For regular outdoor cleaning of organic stains such as grease, motor oil, mold, plant and animal waste Oxy-Klenza™ can be used. Oxy-Klenza™ is a powerful triple action outdoor cleaner and stain remover for natural stone and other hard porous surfaces. The oxygen, alkaline and detergent based cleaner breaks down organic stains and soiling.
For indoor cleaning:
For regular indoor cleaning of organic stains such as oil, mold and food grime Rejuvenata ACTIVE™ can be used. The powerful active enzyme cleaner concentrate is specially designed for natural stone and other hard surfaces.
For countertop cleaning:
Rejuvenata™ for countertops
Countertops are a key feature of any kitchen. It can be a space for food preparation, dining and even acting as a second table. For this reason porous natural stone countertops usually need to be cleaned daily.
Rejuvenata™ spray for countertops is a pH neutral cleaner specially designed for natural stone countertops. The everyday cleaner is food safe and contains a tiny amount of invisible sealer to increase protection from staining. Rejuvenata™ spray’s mild, natural citrus scent provides a refreshing aroma.
For cleaning efflorescence, limescale, rust marks, and grout haze on acid sensitive surfaces
Note on not using acid
Eff-Erayza and other acid cleaners are not suitable for acid-sensitive surfaces such as limestone. If used on these materials the cleaner will leave a permanent etch mark on the surface.