When the power of reverse-swing was finally understood by the international cricket community - it happened in the summer of 1992 when Wasim Akram and Waqar Younis made the ball talk all over England - it was immediately labeled an unorthodox skill. Other bowlers couldn't do it, and the batsmen couldn't play it. The technique acquired a sinister and improper air.
On closer attention, you realise that 'reverse-swing' is actually quite a presumptuous label. Who decided which kind of swing is reverse and which is regular? It's a significant question, because being the reverse of something can carry the added burden of impropriety. Why should the way it swings in the subcontinent carry that burden, and why should the way it swings in England be considered the prescribed way?
English fans may not have seen it before, but reverse-swing had been around in the Test arena for a long time. In 1979, Sarfraz Nawaz used it to take seven wickets for a solitary run in a match-winning spellat Melbourne. At Karachi on Christmas Day, 1982, Imran Khan bowled a famous spell of reverse-swing against India during which he was, for all purposes, unplayable. Sarfraz and Imran had demonstrated for anyone caring to notice that reverse-swing enabled unprecedented control and movement. It allowed the ball to turn corners, and get into spaces that didn't even exist, such as the junction between Sunil Gavasker's bat and pad.
Ian Chappell, cricket's foremost logician, has frequently argued that qualifying swing bowling with appellations like 'reverse' or 'regular' is pointless because, basically, it is all just swing - lateral movement of the ball while in flight. The argument is sound, but the term 'reverse' remains entrenched.
As a physical phenomenon, reverse swing does have a distinct technical basis from the early swing that typically occurs under English or similar conditions. Air passing over a cricket ball creates turbulence, and the theory is that the two kinds of swing result from the ball responding to surface turbulence in opposite ways. In conventional swing, the ball is believed to move towards the side of greater turbulence, while in 'reverse' swing it goes the other way, away from the turbulence, and hence the term. Differential turbulence between the ball's two halves can be created either by angling the seam (as in new-ball or conventional swing), or by allowing one half to scuff up through wear and tear while the other half is kept obsessively polished and smooth.
Perhaps a more appropriate name for reverse-swing would be super swing, because reverse-swing has super proportions. The ball moves a greater distance, and with more accuracy, than a ball swung by angling the seam. In any case, to a batsman who has just missed the line, the physics of the movement is irrelevant. What really matters is whether the ball moved, and how much. In terms of the contest between bat and ball, the key variable that distinguishes the two types of swing bowling, therefore, is not qualitative but quantitative.
It is often said that reverse (super) swing is poorly understood, but in fact it is a simple and straightforward technique that you can try in your own backyard. All you need is a tennis ball, a roll of electrical insulation tape, and a set of stumps to aim at. Cover one half of the ball with strips of tape and hold it down the center, with the taped side entirely to one side. For a toe-bruising yorker, keep the taped side towards leg and deliver the ball aiming for second slip. About two-thirds of the way the ball will curve like a banana and crash into the base of middle and leg. The faster you are the better, but you don't have to be very quick to create the effect. To bowl a menacing outswinger, keep the taped side facing off and aim for fine leg. The physics is elementary. The smooth, taped side creates less turbulence than the uncovered, rough side of the tennis ball. Less turbulence means lesser resistance, and the ball moves in that direction.
If there is any kind of swing bowling that is shrouded in mystery it is, in fact, the conventional variety. It is more of a natural gift over which the bowler exercises uncertain control. As Bob Massie's famous example shows, you can sometimes go an entire career without being able to reproduce it.
They say in traditional swing the ball deviates away from the shiny side. Since a new ball, with equal shine on both sides, can swing just as much, this can only be half-correct, if at all. Another confusion is that the direction of the seam, supposedly the basis of the movement, turns out not to be crucial. The most important variable in traditional swing is probably the angle - the mechanics and trajectory - of delivery.
Who would know more about English swing bowling than Ian Botham? In Ian Botham on Cricket he writes that the direction of swing is determined by the dynamics of the bowling action. "I honestly think that if your action was very sideways-on it would still be possible to bowl an out-swinger with the ball held the other way," he observes. Imran experienced something similar in England; in his autobiography, he records that it didn't matter how he held the ball, his natural action made every delivery come into the right-hander. In his crisp memoir, Strike Bowler, Craig McDermott alludes to the same thing. "The key to swing is the way you cock your wrist before delivering the ball," he writes. "By varying the angle of the wrist, you change the direction of swing."
The most perplexing thing about traditional swing is the discrepancy between bowling experience and scientific analysis. In 1983, a group of physicists from London's Imperial College led by Dr. Rabi Mehta conducted a painstaking study of factors affecting cricket ball swing, publishing their results in the respected scientific journal Nature (Volume 303, pages 787-788). Using angled-seam balls propelled into a wind tunnel, they found that the best swing took place at speeds of around 70 mph (112 kph). They also found no correlation between swing and air dampness or humidity. Any swing imparted by the mechanics of the bowler's arm and wrist may not have been fully modeled in the experiments. It is a reflection of the complexity of swing bowling that despite rigorous scientific scrutiny, questions remain unanswered.
Super swing is simpler to understand, easier to learn, more accurate, and perfectly reproducible. Delivered at speeds over 90 mph, it can be a lethal weapon, some would even say a weapon of mass destruction. It doesn't matter what your action is or how you cock your wrist. All that matters is which way the smoother surface is facing. Provided there is enough difference between the rough and shiny sides, the ball will always move towards the smoother surface. It isn't the 'reverse' of anything. That's just the way it is.