Lecture on Material

Rowden Fullen (2007)

• The cheating rubber
• Table tennis and other racket sports
• Principles of table tennis
• Diminishing ball speed
• Mechanics of flight, bats and rubbers
• Racket coverings, standards and sponges
• European women at world level
• Authorised racket coverings
• Rubbers – reverse to material
• Rubber categories

1. THE CHEATING RUBBER

Long pimples come in many variations and different friction levels. They are not always easy to play against but their use is quite legal. They have however always been controversial.

• Long pimples allow easy control of spinny balls – TRUE but is easy control better control? Playing a variety of strokes with long pimples against different spins is very difficult!
• These rubbers are difficult to play against if you don’t know the right tactics – TRUE but whose fault is this? You may as well make excuses that left-handers, pen-hold players and defenders are equally difficult.
• You have to think when playing against long pimples – TRUE but if you normally play without thinking then you are playing with one less weapon than your opponent!
• Top players never play with long pimples – UNTRUE some top players do and some world champions have!
• Long pimple rubbers allow you to do nothing and just wait for your opponent to make a mistake – if you wish to use the rubber in this way you can, but it’s not the most effective method and in any case winning by forcing the opponent to make errors is quite legal.
• Long pimples are more effective at lower levels – TRUE but this is still nothing to do with cheating.
• Returning the ball without taking any risks is easy with long pimples – UNTRUE it can be very hard to return a very difficult ball so that the good opponent is unable to attack. Also at top level the golden rule is ‘don’t let the opponent attack or at least don’t let them attack hard’.
• It’s easier to do more things and do them well with a normal reverse rubber – TRUE so this should make it more difficult to be successful with long pimples!
• Long pimple players have it easy and don’t need to work – UNTRUE good long pimple players have to work twice as hard to master both rubbers on both wings!
• Some pimple players use the rubber to cover a weakness – TRUE but some players use pots of glue, blast every 3rd ball and have little control over their reverse rubber. However this is then called good tactics or positive play, never cheating!
• There is considerable variation in how different long pimples play – TRUE but again it’s up to you to update your knowledge and your tactics instead of just whinging. There are far fewer legal and deceptive rubbers since the aspect ratio rule.

2. TABLE TENNIS AND OTHER RACKET SPORTS

No two players play the same — there is a product however for every variation of style and this makes the choice of the right combination just for you an extremely difficult decision. Of all racket sports table tennis is the one which has by far the biggest variety of racket coverings. This of course creates a bigger variety of playing styles and tactics, especially amongst the women, who in most cases lack the power of the men. In tennis for example one may have over-sized racket heads or higher and lower tension in the strings, but basically one racket does not vary radically from the next — the same applies to badminton and to squash.

However it is not only the racket which is very different in table tennis with its many permutations of spin, speed, control and effect, but also the ball which makes the game rather more difficult to master. This is because the ball is so light, takes much more spin than the balls used in other racket sports and slows so much more rapidly in the air. Not only must the developing player be aware of what his own weapon can do, but also of the characteristics of the opponent’s weapon and what his opponent is likely to be able to achieve with it. But equally, to be effective the player must be aware of what the ball will do after contact with the racket, both in the air and after the bounce. In other words to be proficient at our sport the player requires to be rather more aware of the mechanics and science of table tennis and especially as we have the least time of all ball sports to react, recover and play our next shot.

What we also have to bear in mind is that to reach full potential we have to select the weapon which most suits our style of play and which will enable us to develop in the right way. It would be of little use for a strong topspin player to use 1.0mm sponge as the ball would not be held long enough on the racket. But such a thickness might well benefit a defender who wishes to initiate heavy backspin. The beauty of table tennis is that you can tailor the equipment you use to be of maximum benefit in your long term development – the main stumbling block however is that there is such an immense number of sponges and rubbers on the market, that it can be difficult if not impossible to find the right combination to suit you. However if you are a player who is always looking to develop and to move on, then often such evolution will involve experimentation with differing materials. We must also bear in mind that there will be changes in players’ styles and tactics over the years which will require research into different playing surfaces.

Above all what we must be able to do before we select ‘the weapon’ is to analyse our own game in detail and decide just what characteristics the racket of our choice should possess and what we should be able to do with it. Do we need speed, spin, control, feeling or effect and in what quantities and combinations? If we ourselves are not capable of doing this then we will need to call in outside help in the form of trainers or coaches who know how we play and how we win points.

Once we have our style analysis the first step is to research the blade. The choosing of a blade is a rather more personal matter than the rest of the equipment and it should feel right both in terms of speed and especially of weight. Blades usually vary from about 65 grams up to about 100 grams – very few players would want to use a blade heavier than this. Tests in a number of countries appear to indicate that there is an ideal racket weight for the player at differing stages in his or her development and variation by even a few grams can cause a drastic loss of form. We must also bear in mind that the thicker sponge and rubber sheets (2.2 and maximum) and particularly those with harder sponges can add considerably to the overall racket weight (Both Western and Chinese reverse can weigh around 40 – 45 grams, pimples out between 28 – 38 grams and long pimples without sponge as low as 14 – 20 grams). Handles are also important and players often have a preference for one shape or another. In the case of ‘twiddlers’ the type of handle and the width of the blade shoulder too may assume more importance.

The second stage is to decide on the sponge, both thickness and softness/hardness. Thicker sponges are more effective for topspin play and have better control and feeling for blocking. Medium sponges (1.7 – 2.1) are good for close-to-the-table play and drive/counter-hitting, while the thin sponges are best for defence, especially where heavy spin is needed. The softness of the sponge is of particular importance in the areas of control and effect – soft sponges are better for blocking, attacking from an early timing point and for achieving different effects when using pimples. Harder sponges give more speed and a faster and lower ball after the bounce when combined with topspin.

Finally we come to the selection of the rubber top sheet. Here we are concerned with softness, thickness and the ‘tackiness’, the friction of the rubber. Softness and thickness are important because these characteristics allow the full influence of the blade and the sponge to come into play. For example the combined thickness of ‘sandwich’ rubber (the rubber and sponge layers) must be legally no more than 4.0 millimetres and the rubber itself is not allowed to be more than 2.0mm. There is however no legal requirement as to the thickness of the sponge. What has happened over the last 5 – 8 years is that with modern manufacturing techniques, the rubber layer can be produced in much thinner sheets (as low as 1.1 – 1.2mm) and as a result sponge layers have been able to grow in thickness up to around 2.8mm. This obviously is very good for the loop players. ‘Tackiness’ is also important to many players, both in the service game and in the rallies. Many high friction rubbers have other qualities too, such as being able to slow the ball quite dramatically in short play.

3. PRINCIPLES OF TABLE TENNIS

1st Principle — ADAPTABILITY

The main problem in our sport is the instability of the environment. The player must be effective in a constantly evolving situation. High level players for example learn from mistakes immediately and do not repeat errors - they find effective solutions rapidly. As Waldner says in his book - ‘In order to win big titles, you must master play against all playing styles. Therefore, you must regularly practice and compete against players of different styles. The most important styles to embrace are loop players (maximum topspin), attackers (maximum speed) and choppers (maximum backspin). Another important aspect is play against left-handed players. I would like to remind you that both right- and left-handed players spend 85% of their playing time playing against right-handed players. To be successful against both right- and left-handed players requires well-developed technique and very good balance.’

Players can reach a high level (even playing for their country) and still have major limitations in their game if they ignore this advice. The lack of ADAPTABILITY or inability to play against a rubber or style is ONLY your fault (no-one else’s) and the problem is in your early training.

It is interesting to note that in some countries in Europe, France and Germany for example, there is strong evidence in players as young as 9 - 10 years of age of a highly developed adaptation capability and their coaches are to be commended. On the other hand in countries which one may consider to be highly progressive, such as UK or Sweden, the same capability is severely lacking even among players in their late teens or those at senior level.

Rubbers - To access the best rubber for your particular style of play is a monumental task. There are over 1000 differing rubbers and if you consider all the sponge thicknesses probably around 4000 or more variations. The most rapidly increasing sections are China reverse and long pimples. Chinese rubbers are popular because of the low cost, increasingly better quality, good choice and variation and the possibility of marrying together a variety of sponges and rubbers. Especially in the case of pimples and women’s play it is possible to experiment with differing effects by using differing sponges and differing hardnesses of sponge under the pimples. In the West our approach to rubber selection is usually rather amateurish.

However we can’t just talk about rubbers - we must investigate sponges and what happens to the ball in the air. If we don’t understand how the ball behaves during its trajectory and after the bounce it’s hard to understand the advantages and disadvantages of differing materials. Without understanding what happens to the ball in the air and after the bounce and the 3 speeds - off the bat, through the air and after the bounce, one doesn’t see the whole picture and is not fully informed. Also much of this material unfortunately is just not available in the UK.

2nd Principle - TIME AND THE CONSEQUENCES.

In the case of the average person reflex speed is around 0.20 of a second; one or two rare individuals may be faster than this. A smash on the other hand takes 0.10 to cross the table from end line to end line.

As we can see from (J) there is a big difference looping close to the table and executing a similar stroke three metres back. If we feed in an initial speed of 15 m/second, ball (1) will reach the other end of the table in 0.2 of a second or slightly less and will then have a speed of 10 m/second - ball (2) on the other hand will take around 0.5 of a second and the speed will have dropped to 7.0 m/second. We must also bear in mind that even at relatively slow speeds, say an average of 40 kph, the ball will cover the length of the table in about 0.25 of a second which is just within the limit of human reaction time for the average player.

In our sport the importance of ‘reading the play’, of seeing what is happening as the opponent plays the ball (or in fact 5/6 centimetres before ball contact) is absolutely critical. We must use all possible cues (body and arm action etc) in order to give us every possible advantage.

It is also true to say that our sport is becoming faster and faster and as a result technique (and the economy and streamlining of all technical movements) becomes more and more important. Balance and ‘retained square-ness’ are especially vital. Because much of our technique has to be automated and because we play best when we react subconsciously, we have to make sure that the automated reflexes are absolutely flawless. With today’s time restrictions there is no room for manoeuvre.

Above all training must provide continuous and evolving possibilities for our athletes to apply a variety of techniques in a realistic and competitive environment. Coaches must ensure that players, as they progress through the learning process, are able to identify the most suitable technique and apply this in a variety of differing situations. In other words because we are facing a rapidly changing situation all the time we play, to cultivate adaptive intelligence is absolutely vital. This is the ability to evaluate a scenario in an instant, take in all the immediately available solutions and then take the best action. Often this is called reactive thinking - the ability to think clearly under pressure and use any available means to hand to resolve the problem.

4. DIMINISHING BALL SPEED

At what speed does gravity come into effect? With a speed of 8.5 m/second (30.6 k/hour, 19.125 mph.) the air resistance is about equally as strong as gravity. Below this speed the effects of gravity come into play very quickly. Air resistance however increases or decreases by the square of the speed. This means that a doubling of the speed to 17m/second signifies a fourfold increase in air resistance. Halving the speed to 4.25 m/second would bring about a reduction in air resistance to around one quarter of gravity. In the case of fast counter play a normal speed would be in the region of 13 — 15 m/second which means immediately that it’s always the air resistance which is the dominating factor in the early stages of the ball’s trajectory.

We must also bear in mind that even at relatively slow speeds, say an average of 40 kph, the ball will cover the length of the table in about 0.25 of a second which is just within the limit of human reaction time for the average player.

5. THE MECHANICS OF FLIGHT, BATS AND RUBBERS

Mechanics of flight

Once the ball has left the racket, the trajectory and direction is determined by the power and spin fed into the stroke. The trajectory itself is determined by gravity, the air resistance and the influence of the spin. A similar stroke will always produce a similar result in terms of spin, speed and direction.

However significant variations can and do occur. The major one is in air pressure and when we talk about height above sea level. At 1000 metres air pressure sinks by 12% and at 3000 metres by up to 30%! This has a major impact on both the air resistance and the effect of the spin on the ball in flight. A major championship event played for example in Mexico City will result in the ball ‘flying’ in an unusual manner and the players must be ready for this, as the trajectory of the ball will not conform to expected criteria.

Let us look however closely at the ball in the air and before the bounce. What we must first understand is that the ball surface is not smooth and contains pockets of air in the surface which react with the flow of air against the ball. We do know that in the case of the top part of a topspinning ball, this spins against the oncoming air while the bottom part is in the same direction. Therefore we have an area of high turbulence at the top and low turbulence at the bottom. However the air flow round a ball moving at high speed changes from turbulent to laminar as it slows down in the air and this is what causes the ball to dip. Just what do we mean by this?

At the ‘static point’ which is the leading point of the ball at speed there will be an ‘eye’ like at the centre of a hurricane where there is an area of pressure. The flow of air around the ball however will in the initial stages of flight as the ball leaves the racket at speed, be chaotic or ‘turbulent’ in nature. By this we mean there is no smooth pattern of air molecules flowing around the surface of the moving ball.

It is only as the ball slows down that a pattern starts to emerge and the air flow around the ball forms a more ordered outline. We call this a ‘laminar’ effect. It is of course at this stage that the high and low pressure areas forming on different parts of the ball’s surface have a direct effect and as a result the ball is forced upwards or to dip sharply downwards on to the table.

After leaving the racket regardless of the spin, speed or direction, the ball is influenced simply by 3 factors - gravity, air resistance and spin (Magnus effect). In the case of topspin, gravity and the influence of the spin work together giving a more arced trajectory. With backspin gravity and the spin factors work against each other so that the ball will rise initially in a curve before dropping sharply when gravity predominates over the lessening spin. Gravity is always equally strong and always directed downwards. Air resistance is always against the direction of travel and its effect is strongly influenced by the speed of the ball.

But just at what speed does gravity come into effect? With a speed of 8.5 m/second (30.6 k/hour, 19.125 mph.) the air resistance is about equally as strong as gravity. Below this speed the effects of gravity come into play very quickly. Air resistance however increases or decreases by the square of the speed. This means that a doubling of the speed to 17m/second signifies a fourfold increase in air resistance. Halving the speed to 4.25 m/second would bring about a reduction in air resistance to around one quarter of gravity. In the case of fast counter play a normal speed would be in the region of 13 — 15 m/second which means immediately that it’s always the air resistance which is the dominating factor in the early stages of the ball’s trajectory.

Bats, rubbers and sponges

Questions relating to materials and the differing spins and effects can be rather more complicated as the manufacturing companies have not tried to create standardised tests to measure exactly what their products can do. Often experienced players or testers (or in some cases not so experienced) categorise rubbers in terms of spin, speed and control, but obviously these classifications are purely subjective. Different players will for example use rubbers in differing ways and one player will often be capable of getting far more out of a particular rubber than another player would. Such ‘subjective’ testing can give some useful information but helps little in giving any base for objective measurement when comparing products from different manufacturers. Also materials and indeed techniques and tactics are constantly in change - it is necessary that we always have an open mind and are ready to look at new ideas and ways of doing things.

Much of the advertising matter which is written in the various brochures on materials is of very little use to the ordinary player and often misleading. The hardness of the wood and the make-up of the ply, how it is bonded and whether you have carbon fibre or titanium mesh layers will all affect the speed and control. Generally one ply will be more rigid and the ball will kick off the blade quicker, multi-ply will be more flexible with more control and stability. The choosing of a blade is a rather more personal matter than the rest of the equipment and it should feel right to the player. Tests in one or two countries appear to indicate that there is an ideal racket weight for the player at differing stages in his or her development and variation by even a few grams can cause a drastic loss of form.

In the interests of weight reduction, the central core of many modern blades consists of a thick layer of balsa wood and the speed comes from the outer veneers of much harder woods often supported by carbon or glass fibre or titanium mesh layers (these supporting non-wood layers should not be thicker than 7.5% of the total blade thickness or 0.35mm whichever is the smaller). According to the rules at least 85% of the blade by thickness should consist of natural wood.

Most rubber manufacturers use speed, spin and control ratings which are at best misleading — many of the tests they use are very simplistic and bear little or no relationship to how a rubber is used in a match. Players also use the same rubber in different ways and with different feel. Let us examine the characteristics of the rubber as it is this which contacts the ball.

• Dwell time — This is how long the ball stays on the racket during the contact phase of a stroke, (bear in mind this is a mere fraction of a second, if you have ever chalked a ball and thrown it to a player who slow loops and tries to maintain a long contact you find that the mark on the ball is never more than one centimetre). Rubbers have different dwell times for different strokes. The ball will be held longer for a slow loop as opposed to a kill. Some players also ‘carry the ball’ longer than others even for the same stroke. A long dwell time will often benefit spinners and blockers while a short dwell time will suit defenders and hitters. The dwell time is also affected by the blade you use and how the ball comes off the racket depends much on the rubber and sponge and how quickly it penetrates through these to reach the wood layer underneath.
• Resilience — The energy stored in the rubber during the contact phase of the stroke. Some rubber and sponge combinations are much more elastic than others and will hold the ball longer on the surface even at a closed racket angle. This stored energy is converted to produce spin. While elasticity levels will certainly increase we must bear in mind that the sponge cannot create energy, but can only minimize energy losses. Compared to a hard bat a ‘sponge’ bat can be swung in a much flatter plane so giving the ball more forward speed with spin. The sponge in fact helps to lift the ball over the net.
• Impact behaviour — A rubber and sponge can have differing performances at different impact speeds. At a slow speed there may be very little elasticity but you may get very good spin and speed when the ball comes into the racket with more pace. When you achieve maximum impact speed you can swing the racket harder but you will get little or no more effect. Some rubbers are said to have good gearing for spin and speed, which means they produce and maintain good effect over a wide range of impact speeds.
• Throw-angle — The angle of the flight of the ball as it comes off the racket surface in the direction the bat is travelling. Differing blades and rubbers affect the throw-angle considerably as will different strokes (the angles would be very different if you were looping for example with very tacky rubber or with anti-loop). The throw-angle will also vary depending on whether the contact is on the outside of the racket or in the middle, or whether low, in the middle or high on the ball (or whether the racket is more closed or open). High throw-angle rubber generally has a higher ratio of spin than speed, compared to low throw-angle rubber. (Flexible, slower blades typically increase the angle).
• Stall-angle — The contact angle at which the speed/spin of a rubber is dramatically reduced — at certain angles all rubbers will stall and not grab the ball (the ball will just drop off the racket, as it sometimes does when it contacts the outside edge). The stall-angle can be used effectively for dummy loops or short serves. A rubber with a wide range of stall-angles (or used with a badly matching blade) will have little or no control. A stall can also occur when the racket contact speed is too fast at a particular contact angle.
• Friction — The grip of the rubber. Under certain conditions and with certain techniques some super high friction rubbers can give less spin/speed than ones with much lower friction characteristics. Sometimes super-grippy rubbers have less spin at high speed — there is a critical level above which little or nothing is gained. Some very tacky rubbers have the characteristic of slowing the ball dramatically at low impact speeds, a function which is very useful in certain strokes. A low friction rubber has difficulty generating speed at closed racket angles. Remember always the friction of many rubbers is impact dependent, they are more effective when the ball is coming at speed.
• Sponge — Sponge can vary from soft to hard and from about 0.4 mm to 2.8 mm and the density of the sponge contributes to the weight of the racket. The amount of spin generated by a rubber is closely related to the elasticity of the sponge (irrespective of the top sheet of rubber), below a certain critical level for a given sponge, the spin of the rubber will be considerably reduced. This can be improved through the correct use of speed glues which will increase the resilience by up to 30%. Players who glue usually prefer soft or medium sponges.Sponges are manufactured in different thicknesses, from around 0.4 up to about 2.8 mm. According to the rules the pimple layer of a sandwich rubber should not be more than 2.0 mm but modern manufacturing techniques have reduced the rubber layer to a little over 1.0 mm, allowing the sponge thickness to be increased accordingly. Sponges are also made generally in 5 differing hardnesses, 23 - 28 (the softest), 30 - 35, 38 - 43, 40 - 45 and 45 - 50. In very general terms most sponges used by European players are in the 30 - 35 range while Asian players use 40 - 45. Many top players especially in the women’s game (and players using material), experiment with differing sponges until they find the most effective hardness for their particular style and/or a hardness which produces maximum effect when combined with the ‘material’ top sheet.
• Glue — Adhesives and glue sheets are used to put the rubbers on the blade. Speed-glues are used to increase the performance of the rubber in respect of spin, speed, control, throw and stall-angles. It is always recommended that you allow each coat of glue to thoroughly dry before applying the next coat — otherwise you can get a ‘mushy’ effect which seriously affects performance when the glue is a little wet. Properly applied speed-glue can increase the spin and speed capabilities of the rubber by up to 30% (remember however that some glues do not work well with certain sponges, especially most hard and more dense sponges). Also the glue must be regularly ‘removed’ from the rubber sheet and the build-up must not be allowed to become too thick. All rubbers (where speed-glue is used) should be taken off the blade as soon as possible after play so that the tension is released. One interesting characteristic of speed-glued rubber is that it has a very predictable effect over a wide range of strokes. Its ability to store energy is nearly constant over a large range of impact speeds, (in normal rubber the storage of energy bottoms out at higher speeds).

6. RACKET COVERINGS, STANDARDS AND SPONGES

Questions relating to materials and the differing spins and effects can be rather complicated as the manufacturing companies have not tried to create standardised tests to measure exactly what their products can do. To assess spin, speed and control some companies utilise a scale of 1 - 10, others from 1 - 12 and still others measure up to 100%.

Often experienced players or testers (or in some cases not so experienced) categorise rubbers in terms of spin, speed and control, but obviously these classifications are purely subjective. Many of the tests used are very simplistic and bear little or no relation as to how a rubber is used in a match. Different players will also use rubbers in differing ways and one player will often be capable of getting far more out of a particular rubber than another player would. Such ‘subjective’ testing can give some useful information but helps little in giving any base for objective measurement when comparing products from different manufacturers. Also materials and indeed techniques and tactics are constantly in change - it is necessary that we always have an open mind and are ready to look at new ideas and ways of doing things.

Sponge can vary from soft to hard and from about 0.4 mm to 2.8 mm and the density of the sponge contributes to the weight of the racket. The amount of spin generated by a rubber is closely related to the elasticity of the sponge (irrespective of the top sheet of rubber), below a certain critical level for a given sponge, the spin of the rubber will be considerably reduced. This can be improved through the correct use of speed glues which will increase the resilience by up to 30%. Players who glue prefer soft or medium sponges as these usually produce most effect.

Sponges are manufactured in different thicknesses, from around 0.4 up to about 2.8 mm. According to the rules the pimple layer of a sandwich rubber should not be more than 2.0 mm but modern precise manufacturing techniques over the last 5 years have reduced the rubber layer to a little over 1.0 mm, allowing the sponge thickness to be increased accordingly (up to a combined maximum of 4.0 mm). Sponges are also made generally in 5 differing hardnesses, 23 - 28 (the softest), 30 - 35, 38 - 43, 40 - 45 and 45 - 50. In very general terms most sponges used by European players are in the 30 - 35 range while Asian players use 40 - 45. Many top players especially in the women’s game (and players using material), experiment with differing sponges until they find the most effective hardness for their particular style.

The softness of the sponge is particularly important when playing with pimpled rubber and this is something the Asian players especially the women have known for many years. Rubbers and sponges are manufactured and sold separately in Asia and it’s easy to combine suitable sponges and rubber sheets. Only recently has this facility been available in Europe. It’s also interesting to note that rubber manufacturers have had considerable dialogue with the top men in Europe to help develop suitable weaponry to win at world level. There has been little or no discussion with the top women in the world who are primarily from the Asian/Oriental block and the production of pimpled rubbers in the West has more often than not been sub-standard.

7. EUROPEAN WOMEN AT WORLD LEVEL

8. AUTHORISED RACKET COVERINGS

http://www.ittf.com(equipment/, Racket Coverings)

Dark sponge, (black, blue, brown, green, purple, red,) should not be used under translucent red coverings. This is liable to make the rubber illegal (Law 2.4.3. governs the use of sponge).

Many racket coverings contain additional text on the rubber surface and all text appearing in the authorised list must be there (eg. ‘D13 S’). The ITTF stamp must of course also be plainly visible.

Altogether there are around 850/1000 rubbers on the authorised list from around 75/86 companies. These are split approximately as follows -

The major companies are as follows -

Rubbers are divided into the following categories on the authorised list –

NB. In the case of all pimple rubbers there must be no less than 10 pimples to a square centimetre and no more than 30 to a square centimetre. In the case of all long pimple rubbers the aspect ratio (ie. The pimple length divided by the pimple diameter) must be larger than 0.9mm but under no circumstances larger than 1.1mm ie. For pimples with a length of 1.8 the largest permissible diameter would be 2.0 mm).

The 850 or 1000 rubbers on the authorised list are divided percentage-wise approximately as follows –

Probably the most significant increase is in the number of long pimple rubbers on the market, up from 66 to 96, an increase of 45%!

9. RUBBERS – FROM REVERSE TO MATERIAL

There are basically seven differing types of rubber surfaces on the market –

• Reverse (normal rubbers Butterfly, Donic, Stiga, Yasaka, etc.) usually with soft rubber sheets and softish sponge around 35 – 40. Used by top men and women in Europe and by the top men in China on the BH side. Very good for looping and the best control for blocking.
• Tacky reverse (Chinese rubbers DHS, Double Fish, Friendship, Globe, etc.) with sticky rubber sheets and usually a harder sponge (around 39 – 45) than that used by top European players. Mostly used in Asia as a FH rubber for the top men and women. Very few players in Europe use this type of surface, except former Asian players. (Used successfully by Drinkall and Knight in the European Youths).
• Anti-spin (Made mostly in Europe, Butterfly, Donic, Stiga, T.Hold, Yasaka but the odd Chinese specimen such as RITC 804). Anti can come in two types, almost no spin or with a little friction. Usually the rubbers are very slow with good control and the ball is slow off the racket.
• Short pimples are between 0.6 – 1.0 in length (rubber sheet only) and made by both European and Chinese companies, Butterfly, Donic, Friendship, Globe, Neubauer, Stiga, TSP, Yasaka, etc. Short pimples vary very much nowadays and some sheets are capable of creating a great deal of spin while others have much less friction. Generally shorter, broader, grippy pimples will create more spin. For maximum effect very soft sponge is a must (30 – 35 but no harder) and top women normally use a thickness of 1.6 –1.8mm sponge while the men tend to go a little thicker, between 2.0 and 2.3 mm. Men of course hit the ball much harder.
• Medium or half-long pimples vary between 1.1 – 1.4 mm. and are made by both Chinese and European companies, Butterfly, RITC, TSP etc. These pimples too vary in grip (some have a more anti-spin surface). The characteristic of half-long pimples is the ease with which players can open against backspin and yet still play a good counter-hitting game with effect. Usually players use these rubbers for attacking and with thicker sponges, 1.5 – 2.0.
• Long Pimples (with friction) are between 1.5 – 1.8 mm. and are made by both Chinese and European companies, Butterfly, DHS, Donic, Prasidha, RITC, TSP, Yasaka, etc. There is an element of friction with these pimples and they are used by many defensive players the world over usually with a thin sponge varying between 0.6 – 1.2. Occasionally attacking players use long pimples with a thicker sponge, Carl Prean, Gary Tendler, Ni Xialan, Deng Yaping.
• Long pimples with an anti-loop effect (between 1.5 – 1.8 mm. too) are made primarily by two companies, Neubauer and Hallmark. These pimples are hard and feel more like plastic than rubber. They have absolutely no friction and all the opponent’s spin is returned.

Maximum spin reversal is achieved by using the rubber sheets without sponge and in the red colour. Spin reversal with a thin sponge (0.4 – 0.6) will be a little less effective for blockers but the thin sponge will give better control with this type of game. Bear in mind that once the player is competent with the long pimples the Ox version will give lower and shorter balls and will add another dimension to the blocking game. In Neubauer’s opinion his Super Block Ox is the rubber which gives maximum spin reversal.

NB. In the case of all pimple rubbers there must be no less than 10 pimples to a square centimetre and no more than 30 to a square centimetre. In the case of all long pimple rubbers the aspect ratio (ie. The pimple length divided by the pimple diameter) must be larger than 0.9mm but under no circumstances larger than 1.1mm). A pimple length of 1.8mm and width of 2.0mm would give a figure of 0.9 – the same length with a width of 1.8 would give a figure of 1.0 – one can therefore say that the purpose of the regulation is to keep long pimples within certain limits and especially not to permit the manufacture of very thin pimples.

If we look at these seven categories in the light of their ability to affect or change the spin on the incoming ball we get results somewhat as follows –

10 RUBBER CATEGORIES

• WESTERN REVERSE
• CHINESE REVERSE
• ANTI-LOOP
• SHORT PIMPLES (0.6 — 1.0mm)
• HALF-LONG PIMPLES (1.1 — 1.4mm)
• LONG PIMPLES WITH FRICTION (1.5– 1.8mm)
• FRICTIONLESS LONG PIMPLES (1.5 — 1.8mm)