Common Problems of Limestone:

Efflorescence

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. STAIN-PROOF^® Premium Impregnating Sealer, formerly known as 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.  

Stains

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.   

STAIN-PROOF has a number of products that can protect against staining and remove those difficult deep stains. 

• Premium Impregnating Sealer 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.   
• STAIN-PROOF Alkaline Cleaner, formerly known as OXY-KLENSA™, 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 

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.   

Freeze-thaw Spalling

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 STAIN-PROOF 40SK Consolidator & Water Repellent, formerly known as 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 40SK Consolidator & Water Repellent will have permanent water repellence. The protective barrier will significantly reduce water ingress and subsequent freeze-thaw and salt spalling.  

Picture Framing

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 Premium Impregnating Sealer provides a deep, water-repelling barrier. This will significantly reduce water being absorbed into the grout and material, lowering the risk of picture framing.   

Acid-Etching

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:

For countertops:

Dense Stone Impregnating Sealer - 2 coats

To protect natural stone countertop we recommend using STAIN-PROOF Dense Stone Impregnating Sealer, formerly known as 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: STAIN-PROOF’s impregnating sealers will not prevent acid etching because they do not physically prevent an acidic substance from touching a surface. 

For natural look:

Premium Impregnating Sealer - 2 coats

For protection against water and oil-based stains and efflorescence we recommend using STAIN-PROOF Premium Impregnating Sealer, formerly known as 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. Premium Impregnating Sealer creates a chemical bond inside the pores, permanently becoming part of your material. 

Waterborne Dense Stone Sealer - 1 coat

For indoor applications, we recommend using STAIN-PROOF Waterborne Dense Stone Sealer, formerly known as META CREME™, 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. Waterborne Dense Stone Sealer 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:

Paver Enhancing Sealer - 1 or 2 coats

For color enhancement of man-made surfaces, we recommend Paver Enhancing Sealer.Paver Enhancing Sealer offers both rich color enhancement and water and liquid protection through a patented combination of silicone technology.

For surfaces in saltwater environment:

40SK Consolidator & Water Repellent - Dip Seal

We recommend using STAIN-PROOF 40SK Consolidator & Water Repellent, formerly known as 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. 40SK Consolidator & Water Repellent 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:

Alkaline Cleaner

For regular outdoor cleaning of organic stains such as grease, motor oil, mold stains, plant stains and stains from animal waste STAIN-PROOF Alkaline Cleaner, formerly known as OXY-KLENSA™ can be used. Alkaline Cleaner 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:

Daily Floor Cleaner

For regular indoor cleaning of organic stains such as oil, mold stains and food grime STAIN-PROOF Daily Floor Cleaner can be used. The powerful active enzyme cleaner concentrate is specially designed for natural stone and other hard surfaces.

For countertop cleaning:

Daily Countertop Cleaner

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.

STAIN-PROOF Daily Countertop Cleaner 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. Daily Countertop Cleaner 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

STAIN-PROOF Acidic Cleaner, formerly known as 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.