Monthly Archives: September 2012
The shine is more evident in mirror polishing of marble, hence is worth the time and money it demands.
Just when we feel we know enough about a material, it is time to recheck – there could be aspects we took for granted and erred in its application. Many of us are so familiar with marble that the danger of some ignorance costing us dearly is always around! This awareness dawned even as I was writing on marble, for the more one wrote, the more the issues that still remain to be discussed.
Ask anyone about the most commonly known aspect of marble and the immediate answer could be about polishing. The bright appearance achieved by polish has been among the reasons for the popularity of marble. The simpler and cheaper method is wax polish, done with three rounds of polish with carborundum stone and finished with wax application.
The more common approach is called mirror polish, seven rounds of polish with carborundum and final tin oxide buffing on top. The wax reflects less light and wears fast, but the mirror polish shines better, hence the latter is worth the time and money it demands. While pre-polished marble slabs can be organised, for the best results, they need to be polished at site, during the construction.
The base layer for a marble floor should be a good mix of concrete, evened and levelled with 1:6 mortar on top around 1 inch thick. Cement slurry acts as the final base layer and the joints are better finished with matching pigmented material especially available for the purpose. In perfectly cut and laid marble, joints can be finished with minimal visibility. Epoxy joints reduce the possibility of white cement joints gathering dirt, but are slightly costlier. Due to its high surface density and particle characteristics, marble can be slippery after fine polish, especially in bathrooms, staircases and kitchens. It will be safe to avoid them in such areas, avoid tin oxide finish or ensure alternative anti-slippery finishes.
Grains and patterns
Matching the grains and patterns between adjoining slabs are a much talked about expectation in marble floor, which can be ensured by collecting all slabs from the same boulder and placing them carefully. White marble slabs can be laid over white cement slurry, to increase the sense of whiteness in the finished floor.
Marble is known to get stains, which can be partly or fully removed by applying wet marble powder or by polishing. No acids, chemical cleaning liquids, alkalis or detergents should be used.
The water in the base mortar gets partially absorbed by the marble, it being a porous material, reducing mortar strength. Immersing the slab in water for a few hours before laying helps reduce this absorption.
While marble is a natural material, hence eco-friendly, it is not among the low energy options. Considerable energy goes in the quarrying, sizing, cutting and transporting process.
There are also wastages at quarry sites. Once brought to site, it demands many rounds of polishing, further consuming energy accordingly. However, the saving grace lies in marble being a natural material that lasts long.
Among materials, marble seems to be still going strong despite the recent advances in ceramic and vitrified tiles and holds the top position in customer choice.
It is amazing to see how certain ideas and practices defeat the onslaught of modernity. They simply continue to rule the construction world unfazed, while many others phase out. Among materials, marble claims such a position, which despite recent advances in ceramic and vitrified tiles holds the top position in customer choices. Globalisation has added more values to this wonder material, with imported varieties also flooding the market.
The wide range of coloured marbles makes it an ideal choice for interiors, where colour matching is a major concern. The imported marble offers more choices in colour and pattern, but is much softer, hence has surface cracks.
While epoxy coating helps in concealing them, they have chemical-based finish, hence not very ideal. Though the surface of imported slabs takes excellent polish, the cracks become increasingly visible with wear-and-tear across the years. Generally with a much higher price tag, the imported marble could be considered if no other viable alternative in Indian marble is preferred.
Polymerised composite marble is a new trend during the recent years. Powdered marble is mixed with epoxy glue compound as needed to generate blemish-free, crack-free, ready-to-use marble slabs to perfect dimensions in never seen new patterns. Since we can create much richer appearance in these industrialised processes, they can be produced with high reflective surface, even pattern, seemingly invisible joints and luxurious looks. While they have the said advantage, besides saving time in laying, their embodied energy and costs are so high that the choice should be considered on a judicious ground. After all, they are artificial products.
The little drawbacks…
Generally marble is among the cool materials, with low heat absorption, making it a good choice in warmer regions. However, people who sense cold faster than others and are vulnerable to health issues, end up wearing up home slippers! Another contradiction in marble is the way it shines after polish and stains because of sparse use. Areas under less use like room corners appear much dull compared to the central areas where people routinely walk, indirectly polishing them and keeping them fresh and shining.
But despite such negative marks, marble continues to score high in construction industry.
Though not quarried at every place and demanding much energy in transportation, marble could still be considered as a material for sustainable architecture. It is naturally procured and minimally processed.
The construction field is very democratic — it can popularise an aristocrat material, making it an everyday ordinary choice. Luxury needs may become necessities and the exclusive may turn commonplace. Among the best examples to illustrate this phenomenon is marble as a flooring material.
Once hailed as part of royal mansions and great monuments, today this wonder material goes all over India, at a price many prospective building owners can afford. Though not quarried at every place, and demanding much energy in transportation, marble could still be considered as a material for sustainable architecture, being naturally procured and minimally processed. Rated among the construction materials with the longest life span, as could be proven by the many Greek and Roman monuments in marble surviving beyond 3,000 years, we have a green choice.
Rajasthan is the main source of marble in India, where large blocks are quarried, sliced into slabs and further cut into smaller tiles – each for its specific application. The blocks go for sculpting, slabs for floors and tiles for affordable construction and table tops. It is a common practice to lay the floor with slabs from the same block to get continuity of grains between slabs. The tiles are much cheaper, but the surface texture and grain may not match between adjoining tiles, creating a patchy appearance. The material is known for its longevity, though it develops subtle surface scratches, which luckily do not show up always. However, no heavy or sharp object should fall directly on marble slabs, for it is vulnerable to cracking.
Marble can be used in all areas of a building except the kitchen and bath floor. Acids and alkaline materials tend to get absorbed, leaving behind stains and pitting. When exposed to the sun and rain, marble performs well initially, but over the years does not appear very fresh, hence shading the external marble floors is desirable. Even in indoor usage, areas where we regularly walk upon appear better than corners and less used spaces, which appear dull over time. Theoretically, it is possible to re-polish marble, if we can take the trouble of getting it all done in a lived-in building!
The white marble, especially Makrana, coming from a place of same name, rules the marble world. There is a wide variety both in colours and composition in Rajasthan marble, but unfortunately not well known to outsiders. Many of these lesser known marble are equally good for specific purposes.
The Centre for Development of Stone, Jaipur, has been intensely involved in promoting this range and make them available to people across India. It is a fact that even the greatest of ideas would not have been known if not for some patronage. No wonder, if we think marble, we think Taj Mahal. But equally well, if we think marble, we can also think building naturally.
Generally available in grey shades, it lasts long without surface blemishes and is easy to maintain.
The idea of ‘local’ is important in ecological architecture; hence any attempt to promote an outstation material can raise eyebrows. However, certain attitudes like aesthetics, aspiration or cost reduction can justify outstation materials, if done judiciously. This argument can support the idea of getting marbles from Rajasthan or equally good stones from Andhra Pradesh.
What do we get to see if we walk into an old restaurant? Possibly, a chess board pattern of grey and black tiles on the floor, while the restaurant kitchen could be finished with only the grey stone.
Many public buildings built in the near past also exhibit this floor pattern. They are made of Shahabad stone, grey in colour and Cuddapah stone, black in colour.
Shahabad town in Gulbarga district is a centre for Shahabad stone activities. Shahabad is a variety of limestone from this part of Karnataka bordering Andhra Pradesh. Easy to work with and economical, traditionally it has been popular in public buildings. Being fairly hard, it lasts long without surface blemishes. Generally available in grey shades, the neutral colour helps in masking dust and easy maintenance.
We also get Shahabad in chocolate colour, which appears very rich. Both the variations can be used with full polish to get a fine look or less polish for a rustic appearance. Stones are cut into tiles 1 ft. x 1 ft. to lay in single or mixed patterns. A longer length, needed for staircases, can also be procured.
In total colour contrast to the above are Cuddapah stones, again from Andhra Pradesh, with the place name extended to the material. With its near-black colour, Cuddapah offers a great contrast at an affordable price. Comparatively softer, it is safe to use it in conjunction with Shahabad or in areas of lesser wear and tear.
Cuddapah tiles tend to look good after mirror polishing, but appear slightly dull after years of usage. With its tendency of surface layering and pitting, it may not be ideal in all contexts, but goes well with rustic needs and other uses like storage shelves or counter tops. Flooring finished with unpolished Cuddapah side on top creates a textured look, to contract with the possibly smooth looks elsewhere.
Eco-friendly architecture is more theme-specific than material-specific. After all, materials are among the visible components of sustainable architecture, but they come at the end of a decision chain. The idea could be, to begin with, to build natural, hence need natural floor. Coupled with desires like durability, stone may get shortlisted.
Local or outstation stone becomes the next debate, which leads to the specific type of stone. In a way, the starting point is not stone, but being natural.
This note becomes important here, following the possible feeling that Green Sense is promoting materials for eco-build. It of course does so, aiming at sensitive end products, but starting from a deep concern for the sensitive ecological process.
Many Andhra stones cost much less compared to marble and granite, yet provide durable floor finish.
Popularity as a phenomenon is important not only in films or politics, but even in building materials. Shops promote what sells more, and what sells more dominates the market. Markets tend to keep greater stock of such popular items and manage to sell cheap because of sale volumes. An alternative material, possibly equally good, would find it difficult to break into this circle, with lesser demand or low sale volumes; hence higher price or supply problems. Flooring has been a witness to such trends of domination, where a small number of options bag a large number of projects.
Andhra Pradesh is home to varieties of construction stones, including Tandoor, Bethamcherla, Shahbad, Cudappah and such others, which make excellent floors. Most of them derive their name from the place of origin, and today are transported across South India as orders come in. In principle, these Andhra stones cost much less compared to marble and granite, yet provide strong and durable floor finish. All of them come in small sizes, take good polish, have narrow joints, stay fresh even in shelf life and provide varied colour options.
Tandoor is among the more commonly used stones, with a grey or greenish colour. It commonly comes in 2 ft. x 2 ft. size, and slight size variations are possible. The slabs are laid on the sub-floor made of mortar and semi-dry mix of cement and sand, to a perfect level, followed by machine polishing. They never appear overshining, hence maintain a natural feel even after polishing, going well with buildings built with natural materials.
Tandoor is a hard material, hence popularly used in public buildings and houses alike. It is prone for scratch marks by sharp objects, but can be used in all conditions including kitchens and outdoors. Being impervious, if the outdoor floor gathers water, the only way to clean would be with dry mopping. So, better ensure good rain protection.
Bethamcherla is a marble look-alike stone slab, hence popularly nicknamed as Bethamcherla marble. The material comes mainly in golden brown and buff grey colours, though a few colour variations are also available. Being more of tiles, popularly in 10”x10” size, there would be many joint lines visible. The stone tends to be thicker even as floor slab, up to 2 inch thick, where prior floor level calculations become important. Because of the thickness, the edges need to be cut at an angle, to achieve a narrow joint. No two adjacent stones will look exactly alike, unlike marble; hence the floor gets a beautiful pattern. Especially the slabs with golden shade appear every rich when laid across a large area. Recently, special machine-cut thinner floor slabs have also been available. If it is beneficial, the owners can call one agency for both supply and laying, reducing inter-agency problems.
It is amazing to see the range of stones within stones – at least to have a studied choice.