A technical scrutiny of tiles
by Jagvir Goyal

Over the last two decades, provision of tiles on the walls and floors of buildings has seen a tremendous upswing. Bathrooms, kitchens, shelves, facades, garden fountains and home accessories find a greater use of tiles these days. However, the only factor that is examined while selecting tiles is their physical appearance. No attention is paid to the technical aspects of the tiles selected which if considered may lead to a better service by them and their negligible maintenance in future. Surface flatness, edge curvature, warpage, surface quality, water absorption, scratch hardness, abrasion resistance, thermal shock resistance, crazing resistance and resistance to action of chemicals are a few such properties which should be examined before selecting for use in residential, public or industrial buildings.

There were times when only 4 inch size white glazed tiles were used to clad the walls of bathrooms up to 7 feet level. Now the tiles have entered even the drawing rooms. Not only glazed but hand made tiles, hand painted tiles, border tiles and even glass embossed tiles in which the pattern that is embossed in tiles is of multi-coloured glass are being manufactured these days. The designs printed over the tiles are computerised and screen-printed. Not only this, one manufacturer has tried to vivify the grandeur of Indus Valley civilisation by producing tiles called Mohanjodaro collection, carrying various symbols discovered during archaeological excavations. Many manufacturers have collaborated with foreign countries to produce quality-tiles. Such a scenario having tough competition and high creativity demands a thorough study of these products before making the final selection.

Size and finish: Now there is a large variation in the size of tiles. Many sizes, varying from 4”x4” to 16”x16” are available. Though the most preferred shapes are rectangular and square, ‘hexagonal and octagonal shapes are also being produced. The finish may be glossy, semi-glossy, matt, luster and of many other types. Table 1 and Table 2 show various sizes and finishes of floor tiles and wall tiles being produced these days.

Colour: There is a revolution on the colour-front. Such a stunning variety of colours is available that it is difficult to count their number. For instance, one manufacturer is producing floor tiles having 99 colours and wall tiles in 282 colours. Not only this, the manufacturers are ready to produce tiles of the colour and shade as per individual’s choice. Even computerised designing as per individual choice is adopted.

Floor tile groups: Tiles used in floors are now categorised into four groups with respect to the service to be rendered and the intensity of traffic on them. These groups are Group-II, III IV and V. While Group-II tiles are for low and light traffic, Group-V tiles are for very heavy traffic. It is better to specify the group with respect to the intensity of the traffic while placing a demand for floor tiles as this will bring durability and economy. There is no fun in using Group-V tiles in an area where traffic is light. It will cause extra expenditure only. Similarly, use of Group-II tiles in areas of dense traffic such as cinema halls, commercial centres, railway stations etc will result in their wearing out soon.

Table 3 shows various groups of floor tiles, their suitability and their areas of application. Group-V tiles combine high hardness with complete acid and alkali resistance together with high abrasion resistance. Under the abrasion resistance test, a set load of Corborandum, water, water and steel balls is applied on the tile surface using a standard abrasion meter. No abrasion has to be visible after 12000 revolutions. Thereafter, the tile is subjected to Mark resistance test. If no mark is noted, Group-V standards are met with. Such tiles are highly suitable for industrial floorings also.

Tile properties: Different properties have been specified for tiles to be used in walls and floors. Bureau of Indian Standards has evolved IS codes — IS 13753 and IS 13755 for wall and floor tiles respectively. European Standard EN-87 enlists the technical features of wall and floor tiles under the Groups EN159Blll and EN159Blla, respectively. Table 4 shows some important properties of these tiles that should be checked before their purchase. While an organisation can get the tiles tested for these properties, an individual can ask the manufacturer or the supplier to show the test certificate for the batch to which the tiles under purchase belong. Tiles being ceramic products, a variation in their length and shade is likely to occur during the firing process. A buyer should therefore be careful towards these properties. Reputed manufacturers should themselves discard tiles having variation in length and shade beyond permissible limits as otherwise their reputation may be at stake. Presence of just a few such tiles may ruin the aesthetic effect of the tiled wall or floor.

In addition to the properties given in Table 4, the resistance of the tile surface to staining by household chemicals and swimming pool salts should be checked as per procedure laid in European Standard EN122. The manufacturer is bound to mention the abrasion resistance class of the tiles on the box containing them. If in doubt, this test can be got carried as per method of testing in EN154.

Thickness, weight and lot: The thickness of floor tiles varies from 7 to 10 mm. Floor tiles are contained in boxes and number 10 to 50 depending upon the size of the tiles. A box having 25 tiles of size 200x200 mm will weigh around 16 kg while another having only 10 tiles of size 400x400 mm will weight 32 kg. Wall tiles have a thickness of 6 to 8 mm. A box containing 25 tiles of size 200x300 mm will weigh 19 kg and one having 40 tiles of size 200x150 mm will weigh 14.5 kg only. The weight of ceramic tiles for a thickness of 6 mm may be taken as 16 kg/m2. Tiles, these days, are pre-polished, repair free and ready to use. This aspect should also be examined while selecting the tiles.

Manufacturing process: The process of manufacturing of tiles has undergone a significant change during the last few years. Earlier, the tiles used to be subjected to multi-firings. First, these were baked at very high temperatures. Thereafter, glazing which consisted of a mixture of Glass and Zirconium or such elements used to be applied on the tiles. Then the tiles were rebaked. The tiles produced these days are single fired i.e. the manufacturing designing and glazing are done in one process thereby producing more durable and maintenance-free tiles. These single-firing manufacturing processes have been brought by the manufacturers to India from the pioneer countries in tiles such as Spain and Italy. Italy still reigns as the king of tiles. In fact the word “tile” itself has been derived from Italian word “Teluga” which means a covering.

Today, as many as 21 reputed companies are producing tiles in India. Table 5 shows their makes and areas of specialisations in alphabetical order. The competition is fierce. The result is that some of the manufacturers are declaring their product as “exclusive” and not decreasing the costs while other are fighting for survival by keeping very little margins. During the last few years, the prices have come down well. Though hand made and hand painted tiles have uneven edges, odd sizes and very bright colours yet are very costly because these involve carving, are not produced on mass scale and considered to be an exclusive and class item.

Terrazzo tiles: Till early nineties, terrazzo tiles remained under most use Composed of marble chips mixed with coloured or white cement, mechanically ground, hydraulically pressed and then finished, cured and polished, these tiles act as somewhat structurally strong members of the building. Terrazzo tiles, however, need to be polished at regular intervals, the weight is heavy and there is always a tendency of their becoming slippery. These days terrazzo tiles have given way to ceramic tiles. A 6 mm thick ceramic tile serves the purpose at a place where a 25 mm thick terrazzo tile has to be used. There is no comparison of the finish as the ceramic tiles provide a highly attractive surface while the terrazzo tiles begin to look ugly after a year or so. There may be a lot of breakage during the transportation and handling of terrazzo tiles. This factor is also taken care of by ceramic tiles.

Laying of tiles: The walls and floors will come alive only if laying of tiles has been done in a proper manner. How-so-ever beautiful or costly the tiles may be, they will lose all the elegance and aesthetic effects if the tile-joints are thick and uneven; cut-pieces are not used at right places and symmetry is not maintained. Cut-tile-pieces should be used only at the ends (never in the middle) of the walls, on window sills and door jambs. Grouting of joints should be done with a water-proof epoxy grout. No excess grout should be left over the tile surface and should be wiped off at the earliest. The base should be checked to be rough before fixing tiles on it. A guide-rod should always be prepared by the mason before start of work. This guide-rod should carry the markings of tile-size and gaps for grouting among them.

Whenever a laid tile gets broken, it should be removed in a very patient manner by using a chisel and hammer and without affecting the adjacent tiles. Breaking should always be started at the centre of the tile and not from edges. After the removal of tile, the base mortar should also be chipped off. Grouting of the joints should be done when the fixed tile has sufficiently dried up.

Conclusion: The future belongs to tiles. Less involvement of labour, easy maintenance, abrasion resistance, a short time required for laying, wide variety and colours, cost competitiveness, pre-polishing and readiness for use are a few such factors which make tiles a highly attractive item for use. While the present cost of about Rs 20 per sq. ft. for plain tiles and Rs 30 per sq. ft. for special coloured or printed tiles is lesser than what it was years earlier, the prevailing competition among tile-manufacturers promises still lower rates in future.

Matter and antimatter
by Nataraja Sarma

Solving equations which now included the effects of Einstein’s theory of relativity, in 1928 Paul Dirac at Cambridge University in England was able to prove that every particle must have an antiparticle with exactly opposite charge and spin.

Following this argument, according to Dirac, whenever energy is converted into matter according to the famous Einstein formula, E-mc2 an equal amount of antimatter, with exactly opposite properties, must be created at the same time.

Four years later, when looking at the tracks made by cosmic rays in a cloud chamber Anderson and his colleagues at the California Institute of Technology found such an antiparticle. It was as light as the negatively charged electron but its track curved in the opposite direction in a magnetic field. They had discovered an electron but with a positive charge, a positron as it now called.

The positron and an electron get annihilated when they meet and, as a result, two gamma rays emerge in opposite directions, each of 0.5 MeV energy. This, interestingly enough, has medical applications.

A chemical containing a minute concentration of a radioactive element that emits positrons is injected. The scanner looks for these two gamma rays and pinpoints where the chemical is concentrated. This is positron emission tomolgraphy (PET) scanning.

The positively charged proton, which is about 1800 times heavier than the electron has a negatively charged antiparticle, the antiproton.

So, an antiproton and a proton are made from about 1.8 giga electron volts (GeV) of energy. When the antiparticle annihilates a particle of the same kind, this energy is recovered. Collisions of high energy cosmic rays and gamma rays produce particle-antiparticle pairs. Within 20 years of Anderson’s discovery, a number of particles and their antiparticles had been discovered and their properties were measured by looking at cosmic rays and at the big accelerators. Technology for handling elementary particles advanced so fast that beams of antiparticles were produced and made to collide head-on with beams of particles.

Antiatoms such as an antihydrogen atom which is a positron circling an antiproton have been crafted.

In September, 1995, Walter Oelert and an international team from Zulich IKP-KFA, Erlangen, Nuermberg University, GSI Darmstadt and Genoa University synthesised nine atoms of antimatter from their constituent antiparticles for the first time.

Each antiatom remained in existence for about forty billionths of a second. It travelled at nearly the speed of light over a path of 10 metres and then perished by interacting with ordinary matter.

Antiparticles lead to varied and interesting technological innovations. Everyone agrees that in the future, when all fossil resources are exhausted, we must turn to thermonuclear power.

To generate thermonuclear power, one must heat a fuel mixture of deuterium and tritium to extremely high temperatures before ignition takes place. Scientists are trying to accomplish this.

The Shiva project is one concept where powerful lasers are aimed at the fuel to heat it to thermonuclear ignition temperature.

Another proposal is to shoot fast heavy atoms of around one GeV into the fuel and let their kinetic energies heat up the fuel. Antiprotons of one GeV energy would not only transfer kinetic energy but their annihilation would provide an equal amount of energy.

A simple calculation indicates that a milliampere of one GeV antiprotons fired into the fuel deposits about three megawatts at a distance of 10 cm!

From a profoundly philosophical point of view, the fundamental particle-antiparticle symmetry as derived by Dirac raises serious questions.

Why is there only matter and not antimatter in the world? Since the universe we observe is made only of matter, where has all the antimatter gone? Perhaps somewhere out there in the universe, there must be an antiworld made up of antiparticles.

Answers to the above questions are contained in what scientists call CP-invariance.

When the universe was born, there should have been symmetry between matter and antimatter, but it seems that there has been a breakdown of this symmetry, a CP-violation. There is some initial evidence that CP-violation has been seen in the laboratory when the decay of K-mesons were studied and scientists hope that particles which contain bottom quarks will also show CP-violation.

Hydrogen constitutes about 75 per cent of our universe and its properties have been investigated intensively over the last 100 years.

However, it is not yet clear if anti-hydrogen behaves exactly the same way. If it did, then Dirac’s theory must be abandoned or modified. So far antiparticles seem to have the same mass as particles. The meson K and its antiparticle K-bar are of equal mass to an accuracy of one in 1019 while the difference between the B-meson and its antiparticle is one in 1016.

A final word of warning to intending space travellers — if your captain locates a space ship or planet made of antimatter, keep well away from it or else you will be annihilated in a flash of gamma rays and other particles. (PTI)

Cybersurfing with Amar Chandel
Never at a loss for words

The English language has millions of words and their number is constantly growing. Even the largest dictionaries cannot boast of containing all the words. And keeping several of those tomes at your home or office will not only be prohibitively expensive but also cumbersome.

As usual, help is available on the Net, at www.onelook.com. The search engine combines 560 dictionaries that are claimed to have as many as 2840801 words. And chances are that you will find whatever word you are looking for in some of them.

One difficulty is that at times it refers you to several dictionaries and you have to pick and choose. But one or two minutes spent in the search are well worth the effort.

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Similar is the reach of www.theultimates.com when you have to find a particular person or a business organisation or plan a trip. It again makes use of several search engines to zero in on a particular person or place.

The trip planner is oriented more towards the USA. Give your starting point and the destination and you are given the exact map and sundry other details in a jiffy. The maps are detailed and easy to read.

There is also a vast e-mail directory. Small wonder that the site has been assessed more than 22,25,165 times since February 1, 1997.

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Cinema sites are a dime a dozen but www.hindimovie.com is slightly different. It gives you detailed information not only about Hindi films and songs, as the title clearly indicates, but also fills you in about actors, actresses and even temples (of course you know why). The photographs are remarkably good.

There is theatre information also but this is not about the cinema halls in India but about those in the USA and some other countries. The site tells you which film is running in which theatre.

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If you are the kind of person who forgets whom to write and whom to wish, it will be advisable to make full use of reminder services available free of cost on the Net. They dutifully send you an e-mail on the particular day requesting you to do the needful. The Yahoo service is among the most popular. Another one worth a try is www.rememberto.com. It takes in your particulars in precise details and sends good-looking reminder cards.

What if you forget to switch on your computer on that particular day or do not get the Internet connection? Well, those are the kind of difficulties about which no machine can do anything.

Science Quiz
by J. P. Garg

1. While this scientist was working on the passage of electricity through some gas, his wife entered the laboratory and per chance placed her hand over an unexposed photographic plate. Thus a photograph of the bones of anybody’s hand was recorded for the first time. What type of photograph was it? Who was the scientist?

2. The Chandra observatory, named after the late India-born astrophysicist Subramanyam Chandershekhar, was launched recently from the American space shuttle Columbia. What kind of objects does this observatory aim to detect and by which source?

3. With which natural phenomenon are the terms “Baily’s beads” and “Diamond ring” associated?

4. Suggest alternative names for alpha particle, beta particle and gamma ray.

5. Name the compound generally used as a sweetening agent by diabetic patients, whose dilute solution is sweet but concentrated solution is bitter in taste.

6. Which general term is used for plant species that have male and female flowers on separate plants?

7. Nautical mile is a unit used to measure distances at sea and for flying. What is one international nautical mile equal to in metres? What is a speed of one nautical mile per hour called?

8. The plastic used to make bags is usually mixed with a chemical called DEHP to make it flexible. The molecules of DEHP, which are not bound chemically to the plastic, leak and get mixed with the material carried in the bag. What is the full name of DEHP, which is known to cause cancer?

9. What is the technique called that is generally used to determine the location of an object by means of sound waves reflected by the object? Which small animals are known to be able to “see” at night using this technique?

10. What is a self-propelled, underwater missile fitted in submarines, surface warships and aircraft to destroy enemy vessels called?

Answers

1. X-ray photography; German physicist Wilhelm Conrad Roentgen. 2. Quasars, exploded stars, colliding galaxies, black holes etc; by means of cosmic X-rays emitted by these objects. 3. Solar eclipse. 4. Helium nucleus, electron and electromagnetic radiation. 5. Saccharin (ortho-sulphobenzoic imide). 6. Dioecious. 7. I,852 m; KNOT. 8. Diethylhexyl phthalate. 9. Sound navigation and ranging (SONAR), also called echolocation; Bats. 10. Torpedo (The Pakistani aircraft Atlantique shot down by India recently carried torpedoes).

Parachute plane
The Cirrus design SR20 recently became the first plane with its own parachute to be approved by the FAA. During an emergency, the pilot can pull a handle to release the chute. The 55-foot-diametre apparatus will lower the plane to the ground, improving the odds of surviving for the pilot and up to three passengers. Price: $ 169,000. (Popular Science)

Breakthrough in electron microscopy
Researchers at Lawrence Berkeley National Laboratory in USA have reportedly achieved a major breakthrough in electron microscopy as they have made images of columns of carbon atoms in a diamond lattice, only 0.89 angstrom apart — less than one ten-billionth of a metre.

This exceeds the resolution of 1.6 angstroms achieved by Atomic Resolution Microscope (ARM).

Many of the most promising solids, including superhard materials and high-temperature superconductors, incorporate light elements in crystal lattices at short interatomic distances.

The one-angstrom microscope (OAM), developed by Berkeley’s material science division can make images of light elements such as carbon, nitrogen and oxygen in solids at atomic resolution.

The technology will be of help to the industry too as superhard materials and high-temperature superconductors with large band gap energies, incorporate light elements in crystal lattices at short interatomic distances.

Device to design gadgets
A new device to manufacture three-dimensional injection-moulded substrates which can help design smaller & lighter components in electronic gadgets has been developed by German researchers.

The mould electronic device (MID), developed by Fraunhofer Institute for Laser Technology in Aachen, integrates mechanical and electrical functions using a photochemical process to develop the injection-moulded parts, reports Fraunhofer Gesellschaft Research News.

The electronic circuits in cars and portable phones are composed of complex interconnecting elements and are difficult to assemble.

Smallest brewery
British scientists claim to have developed the world’s first personal mini brewery for producing beer at home.

The system, developed by researchers at Miracle Beer Company Ltd in Suffolk, produces premium bitter-type beer and eliminates traditional problems associated with home-brew kits like transferring, temperature maintenance and sterilising, reports British Commercial News.

Called BrewZer, the spherical unit produces ten pints of beer containing 4.5 per cent alcohol by simply mixing a natural powder of malt, hops and yeast with water and leaving it for 14 days to ferment. No chemical additive is needed.

The entire process for brewing takes less than ten minutes.

Identify a person in a crowd
A surveillance computer system that can identify a wanted criminal or a missing child from thousands of faces in a crowd captured on security cameras has been developed by British researchers.

Based on “artificial intelligence”, the system uses closed-circuit television (CCTV) cameras, which is increasingly being used to fight crime, and to spot missing persons quickly and effectively.

CCTV systems have reduced street crime in British cities by up to 50 per cent, but until now they have required security personnel to monitor television screens for hours. It has been almost impossible to pick out an individual from the thousands who pass the cameras.