Stone Sealers

 

Marble & Stone Sealers

Stone installations undergo problems such as picture framing, mineral stains (for example from soluble pyrite, iron sulphide), and water marking and even primary and some secondary efflorescence are well known. Although not all natural stones are prone to these issues there is still a significant number that are. Sealing of a stone has been advocated by some people in the industry as a fix-all for these problems. There have been numerous studies and products for sealing stones, but there is always a apprehension among professionals and customers about different types of Sealers available in the market. Broadly, Sealers can be divided among 3 different categories.

1. Topical Sealers
2. Penetrating Sealers
3. Impregnators

All the products across various categories have their own unique advantages and shortcomings. So, choosing the right kind of Sealer requires a great deal of understanding of the substrate as well as chemical composition of Sealers.

In this article, our emphasis is on imparting a basic understanding about Sealers.

Types of sealers

1.      Topical sealers

Topical Sealers are coatings designed to protect the surface of the stone against water, oil, and other contaminants. They are formulated from natural wax, acrylic, and other plastic compounds. They will significantly change the look and slip resistance of the surface, especially when it is wet.

Advantages

• Some topical sealers contain additives that produce non slip characteristics. This is great for natural stone flooring.
• They create a protective barrier between water and oil contaminants, foot traffic, and the stone.
• They protect the stone from surface scratching and etching caused by acidic materials such as orange juice and coke.
• For the shiny, glossy look, a topical natural stone sealer can produce a gloss that can be buffed. This allows for the maintenance of a high gloss surface.

     Disadvantages

• They alter the appearance of the stone by adding a gloss sheen and may also deepen the color of your stone. This is not so great for a honed natural stone surface.
• Moisture is trapped within the stone. The protective barrier doesn't allow the stone to breathe.
• As they create a film on the surface of the stone, it tends to show scuffs, marks, and paths in heavy traffic areas. But, these marks are removed during the reapplication process.
• These sealers are not breathable i.e. do not allow the escape of water vapors and other gases, and are not effective against salt attack, such as efflorescence and spalling.
• These sealers may be effective at stopping stains but, being exposed on the surface of the material, they tend to wear out relatively quickly, especially on high-traffic areas of flooring.

2.      Penetrating sealers

These sealers penetrate the surface of the stone enough to anchor the material to the surface. They are generally longer lasting than topical sealers and often do not substantially alter the look of the stone, but still can change the slip characteristics of the surface and do wear relatively quickly. Most of them use siliconates, fluoro-polymers and siloxanes, which repel liquids. They often require the use of special cleaners which both clean and top up the repellent ingredient left on the stone surface.

Advantages

• The sealer penetrates into the stone and attaches its protection to the stone walls within the pore structure. This allows the stone to breathe.
• It does not alter the color or sheen of the stone.
• It doesn't need to be reapplied after each cleaning.
• The sealer is not on the surface so the coating won't scratch or scuff.
• A penetrating sealer does not need to be reapplied as often as a topical sealer because there is no surface coating to wear off.

Disadvantages

• Penetrating sealers do not protect the surface of the stone from scratching or etching.
• They do not penetrate deeply enough (generally less than 1mm) to be effective against salt attack, such as efflorescence and spalling.

3.      Impregnating sealers

Impregnators are water-based or solvent-based solutions that penetrate below the surface and become repellents.

They keep contaminants out, but do not stop the interior moisture from escaping. They are considered “breathable,” i.e. they have vapor transmission.

Some modified silane sealers impregnate deeply enough to protect against salt attack, such as efflorescence,spalling, picture framing and freeze-thaw spalling. Some silane stone sealers based on nanotechnology claim to be resistant to UV light and higher pH levels found in new masonry and pointing.A good depth of penetration is also essential for protection from weathering and traffic.

Advantages

• Most impregnators will not change the appearance of the stone.
• Most impregnators do not require frequent applications. Since the impregnator is below the surface, it will generally last several years before reapplication is necessary.
• Most impregnators are not affected by UV light since they are below the surface where UV light cannot penetrate. For this reason they can be used outdoors.
• They are generally hydrophobic (water-repelling), but are also oleo phobic (oil-repelling).

Disadvantages

• Impregnators that are solvent-based produce noxious and flammable vapors during application.
• Solvent-based impregnators are harmful to the environment producing high VOCs (volatile organic compounds). Always check the Safety Data Sheet (MSDS/SDS).
• Impregnators require a semi-skilled person for application. Proper training is highly recommended.
• The initial cost of most impregnators is relatively high.
• Impregnators in general cannot be used below grade to resist hydrostatic pressure. Since the stone is still capable of breathing, water can be forced through the stone by pressure.When choosing the proper product for protection, the above guidelines should help. Always talk with the manufacture or distributer, and let them know where you plan to use their product. They can be very helpful if you tell them all the conditions that apply.

 Comparison Chart of Sealers :

Sealer Type	Use on	Primary Applications*	Type of finish	Performance
Penetrating Sealers	Exterior applications, and thick, smooth or polished stone types such as granite or marble	Exterior concrete surfaces subject to corrosion and freeze thaw damage. Where a natural, matte finish is desired	Provide invisible protection without changing the surface appearance or leaving a sheen	Provide excellent protection against outdoor exposure conditions. Most products are breathable, allowing moisture vapor to escape
Water based Impregnating Sealers	Best on stones with open pores,i.e. marble, limestone, slate, etc.	Indoor/outdoor use	Moderate to reasonable reflective values.	Easy to apply. Very absorbent due to nature of stone
Solvent based Impregnating Sealers	For stones with hard, highly polished, tight pores, i.e. granite, ceramic, porcelain, etc.	Recommended for outdoor use for its resistance to ultraviolet rays from sun. Used in interiors to repel organic and inorganic stains	High gloss, depth and enriched colour	Deep penetrating and long lasting. Initial solvent odor
Topical Sealers	Not for Exterior uses, forms layer so not suitable porous stones		Sheen is observed	Limited durability as they form film on the substrate

*Always check with the sealer manufacturer to verify the compatibility of its product with the decorative surface you plan to apply it to.

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Salt Problems in Egyptian & Turkish Marbles

INTRODUCTION TO EGYPTIAN & TURKISH MARBLES

Egyptian marbles are the oldest and the finest marble products in the world and are available in abundance while Turkey has many assorted types and large volumes of marble reserves due to its geographical position on the Alpine Belt. Both marble types are famous for high lustre and visual appeal in terms of quality, appearance, designs and patterns of numerous sizes and utility. The marble of superior grade do not need any chemical reinforcement like other marble products But, there are certain types of marbles which do have high salt content.

In India, there has been significant increase in the use of such marbles owing to different qualities and factors. But, we have explored some serious problems while installing these stones. 

MARBLE PROPERTIES

• These marble slabs have very low percent of iron content
• They have some disadvantages like the cracks, salt, efflorescence and dis-colouration & low polish durability in certain marble tiles but this can be avoided by using various chemical products

• The qualities and attributes of the various varieties of marble can be identified from the patterns and grains on them

• Densifiers (RachTR Stone Power), Penetrating Sealers (RachTR Top Seal & Back Seal) & Epoxy  Systems are main products to look for while consolidating and finishing the marble slab

EFFECT OF SALT ON MARBLE SURFACES  

The degradation of Egyptian, Turkish or other stones is due to several types of water-soluble salts of minerals such as iron, copper etc. Salt crystallization in porous materials constitutes one of the most frequent causes of decay, in a wide range of environments. These salts can be observed directly as efflorescence and appear and disappear periodically according to the presence or absence of moisture sources. 

Pressures created by crystallization of salt in pores weaken the substrate until its mechanical strength is diminished and damage occurs. Inhibiting or reducing the salt crystallization would therefore prevent or slow down the degradation. This problem represents aggressive deterioration forms that take place on all stone surfaces, mortars and renderings through salinity solutions that are transferred to the stone pores.

  

 

This may be understood from the salt concentration that can be attributed to repeated dissolution and crystallization. When water evaporates, the salt will deposit either on stone surfaces "efflorescence", beneath the surfaces "sub- efflorescence" or within the pore of the stone itself" crypto efflorescence", especially with repeated wetting and drying cycles which finally lead to stone deformation. 

The formation of salt crusts on calcareous stone is the most important chemical reaction involving salinity ground water to cause stone degradation. When these crusts are formed on a porous stone, it disintegrates to a powdered material, while limestone and marble develop thick crusts instead. Furthermore, they are formed when calcite in calcite-cemented sandstone, limestone and marble react with different oxides in the presence of moisture sources through several kinds of chemical reactions.  

Salts manifest themselves in different ways depending on the type of marble used. The problem is not confined to Egyptian marble only. The manifestation of the problem depends on the type of marble used. For example, if the marble has veins, the veins open up when attacked by minerals. On the other hand, if the marble does not have veins, sometimes a layer of white powder can be formed on the surface. Luckily, the powder can be easily wiped off, but could reform again every now and then. Salt forms are aggressive deterioration problems, which occur on all stone surfaces, mortars and renderings through saline solutions transferred to the stone pores. Deterioration of Egyptian & Turkish stones is primarily due to water-soluble salts. The formation of these salts on calcareous stone is the most important chemical reaction involving saline water to cause stone degradation. The studies show that there are aggressive forms of salt affecting the weathered samples; especially those subjected to Na₂SO₄ followed by samples exposed to 1:1 NaCl and Na₂SO₄. The high level of Cl and SO₄, concentrations found on the decayed stone surfaces give an accurate evidence of salt migration. The degradation phenomena resulted from salty decay actions occurs directly through complex mechanisms depending on certain specific factors such as mineralogical composition of stones, stone reactivity and adsorption of some salty ions as Cl-and SO₄.

SOLUTIONS FOR SALT PROBLEMS

Before Tiling

• Marbles being natural products variations in color and veining must be expected

• Prior to laying any tiles inspect the tiles for any defects, correct quantity, color, shape and size

• Experienced tillers /stonemasons are strongly recommended to avoid damage to the material

During Tiling

• All natural stone must be sealed with impregnator such as RachTR Back Seal & laid using specialized stone/marble adhesives. Always clean any adhesive, grout and wax from the surface area of stone

• Adhesives/sand or cement with salt content will re-act with some natural stone and should not be used for stone applications

• Natural Stone should not be cleaned with acid or acid based industrial cleaners

• During the laying process, adhesives and grout must be cleaned off the stone immediately 

Polishing Procedure for Turkish & Egyptian Stones

• Grind the marble using Grit no’s 60 or 100 in Diamond Polish or Grit No. 1 in Granite Polish(Diamond and Granite Polish are two prevalent polishing methods)

• Apply RachTR Back Seal (http://rachtr.com/images/pdf/protection/rachtr-back-seal.pdf) to the substrate so as to harden the surface, enhance the adhesion between stone constituents & make the surface water repellent

• Apply RachTR Epoxy 201L ( http://rachtr.com/images/pdf/epoxy-systems/rachtr-201-l.pdf), on the substrate to fill microscopic minor pinholes, cracks and fissures

• Apply Grit no. 200 (Diamond Polish) or no. 2 (Granite Polish)

• Apply second coat of RachTR Back Seal

• Apply Grit No. 400 (Diamond Polish) or 3 (Granite Polish)

• Apply RachTR Stone Power to further strengthen the stone (http://rachtr.com/images/pdf/polish-systems/rachtr-stone-power.pdf).

• Use next grit, i.e. Grit no. 800 (Diamond Polish) or no. 4 (Granite Polish)

• Apply second coat of RachTR Stone Power

• Use further Grits (no. 1200,1500, 2000, 3000, 5000, 8000 & 12000 in Diamond Polish) & Grit No. 5 & 6 (Granite Polish)

• Apply RachTR Top Seal (http://rachtr.com/images/pdf/protection/rachtr-top-seal.pdf) to prevent absorption of oil, water and other stain causing things

• Apply RachTR Pro-Shine+ (http://rachtr.com/images/pdf/polish-systems/rachtr-pro-shine+.pdf), to further enhance gloss and surface finish

 

STONE MAINTENANCE 

Proper care and maintenance ensures beautiful appearance of natural stone

Cleaning

Only use a mild cleanser such as RachTR XC 1 as harsh chemical cleansers 

can eventually breakdown the sealer.

Acids

Products such as fruit and fruit juice, milk (lactic acid), coffee, tea,household

cleaners contain either natural acids or harsh chemicals that eat away natural

stone and the sealers that are used to protect them. Whenever spills occur wipe

them up. Always use coasters under glasses to prevent unseen spills from

remaining on the stone.

Protection from Heat

Never place a hot dish directly from an oven onto the natural stone - always use

protective mats or trivets. This also protects the stone from chipping that could

occur. 

Stain Removal

• Wipe up spill immediately

• Try to identify what caused the stain

• Use a mild detergent or soap first to try and remove the stain

• No usage of vinegar, lemon juice or other acid based cleaners on natural stone.

• Be aware of “Natural” and “Organic” products – always read the labels.

• Avoid cleaners that contain acid. Read product labels carefully of any bathroom  or grout cleaners.

• Don’t use abrasive cleaners or scourer pads or household grade steel.

• Don’t mix chemicals together. Some combinations could create a toxic gas