Feb
12

What Causes Kicks and Bad or Heavy Contacts in Snooker?

Snooker Ball Kicks and Bad Contacts - a Possible Solution

Problem:

I'm pretty sure snooker ball kicks and bad contacts have nothing to do with Saturn's rings, but it's a great photo :-)Anyone who has watched snooker or played snooker will be familiar with the problem of kicks and bad contacts which occur sometimes when one ball makes contact with another; cue to object.

Sometimes the object ball jumps into the air a few millimetres, sometimes the pace is taken out of the cue ball, and sometimes, the object ball goes off at an unintended angle. Also, I notice that my friends seem to get a lot of kicks just prior to missing easy shots ;-) This aspect of the phenomenon may also be worthy of further scientific investigation.

During friendly games or normal club matches, this occasional irritation is not really a problem. However, when kicks occur during professional matches and tournaments, it can have a significant effect on the players and possibly the outcome. This is when kicks and bad contacts can be costly and they become a more serious problem.

This problem has been around for a long time and there are a lot of theories as to the cause(s). Also, a number of experiments have already been carried out to try to get to the bottom of the issue. Suggested causes include static electricity, chalk dust and atmospheric conditions.

1) Chalk Dust. It is has often been suggested that kicks are produced by chalk dust particles sticking to the cue ball or object ball and preventing a clean contact between the two surfaces upon contact. This is definitely one possibility, but I have an alternative, though still related thought; I think the culprit may be chalk deposits on the table cloth, lying just in front of the cue or object ball, or lying along its trajectory.

There are several reasons why I think this may be a possibility.

  1. Every Time a cue tip is chalked and a ball is struck, a certain amount of chalk falls onto the table cloth.
  2. Sometimes chalk sticks to a ball initially, then is later deposited on the table cloth when it strikes another ball due to the impact.
  3. Players hands are often sweaty especially during high pressure matches or when there are studio lights involved; one of the reasons for constantly wiping cues and hands on dry cloths. Every time a player makes a bridge, some of that moisture is transferred to the table's cloth, which happily absorbs it.
  4. Sometimes the atmosphere in a snooker club, a match venue or even a tournament building is humid, which can add to the moisture already absorbed by the cloth.
  5. Wherever there is a higher concentration of moisture on the cloth, there is more likelihood of chalk dust sticking to it and accumulating. As snooker balls (which are fairly heavy objects) roll around the table during a match, they are constantly steamrollering and compacting this sticky chalk dust; making micro-grooves in it and forming micro-clumps.

I have a powerful, wide-field magnifying glass which I use for assembling extremely small surface mounted components on flexible pcbs. I took this to my local snooker club and after playing a few games with a friend of mine, I examined the table's cloth up close. I literally crawled about on the table.

At first glance the cloth looked a bit ropey but still ok and I couldn't really see any chalk clumps or massive amounts of powder (apart from the many skid marks caused by screw shots). However, when I looked more carefully and strained my eyes, I was amazed! The root or base of the cloth just above the slate (i.e. below the nap) looked like a lunar surface or a battlefield.

A cue ball or object ball parked behind a chalk clump, could be deflected as it initially rolls over itIn some places there were tiny piles of chalk dust around half a millimetre high. Now, a snooker ball travelling at speed would not be affected by these, but imagine if a ball was played very slowly to a middle pocket at an acute angle, or if the object ball was resting just in front of one of these little hills before it was struck.

The deposits of chalk (and other dubious looking debris including hairs, beer, crisps and unmentionables etc.), were not noticable to the naked eye as such, and you wouldn't think they were significant.... but under the magnifying glass it became aparent that if the nap was worn out, or extremely fine (as on a match table), this lunar surface could have a deflective impact on a hard, shiny, round snooker ball.

I've noticed that one of the most common forms of kicks, is when the object ball jumps in the air slightly when hit by the cue ball. This could be caused by a minute clump of chalk dust resting just in front of the object ball, causing it to jump slightly when struck. Also, have you noticed sometimes, a ball played slowly over distance will wander off course? I don't mean because of the nap; it just changes course for no apparent reason - could the cause be a minute clump or wall/groove of chalk dust?

The amounts of dust I am talking about here are very small indeed and will be even less on a tournament table which is cleaned and ironed regularly. However, I still think a considerable amount of chalk dust and moisture can accumulate during several games on a table.

There is no doubt that chalk also sticks to cue balls and object balls during a match (see video - left), and players often have the referee clean balls before critical shots (this relates to the next section on static electricity). Even a few minute grains of chalk dust on a ball at the impact point, could create a noticable deflection.

Again, one possible contributory factor to this effect could be moisture in the air, or more specifically, minute grains and clumps of slightly damp chalk dust picked up from cloth or possibly the chalk on the cue tip is slightly damp too. Maybe players could keep their chalk in a small heated dish or tray to keep it extra dry during a match, instead of in their pockets, which may tend to be slightly more damp because of sweat and humidity).

2) Static Electricity is another common suggestion for the cause of snooker ball kicks and bad contacts. Personally I don't think snooker balls can accumulate enough static charge during normal play to cause a noticable physical deflection. Static electricity can create extremely powerful effects of course, but although static charges exist on and around a snooker table, I think the charges involved would struggle to create any noticable direct effects.

Static electricity is created when surfaces gain or lose electrons. A positive charge is accumulated when electrons are lost from a surface, and a negative charge is accumulated when electrons are gained by a surface. A given surface will have a capacity to hold a certain charge depending upon its surface area, humidity, material, smoothness and many other characteristics.

Snooker balls are made from resins and there are several types/brands. These materials have the potential to accumulate a static charge since they are insulators. In industrial applications measures are often taken to reduce a plastic's ability to hold a charge, or to help it dissipate charges more quickly (the addition of carbon fibre for example). I don't know whether similar measures are taken to improve the anti-static properties of phenolic resin snooker balls, but there are anti-static cleaning sprays available which provide temporary protection.

Given the nature of the materials used in a game of snooker; resin snooker balls, woolen cloth, slate beds, wooden table and cue, leather tips and so on, it's not surprising that static electricity is generated and often blamed for kicks and bad contacts.

Again, personally I think that static electricity may have a role to play in the problem but not directly. I think that static charges, as they accumulate and transfer from place to place (ball to ball for example) are actually attracting and repelling chalk dust particles and also moving them around from place to place.

Think about the way a CRT (glass) TV screen attracted dust particles to its surface, how often they needed to be cleaned. Depending on the polarity of the charge, it's possible that a snooker ball could attract chalk dust particles in the same way. Consider the following events.

  1. Snooker balls are almost always spinning when in motion, not just rolling... this creates sound, heat and vibration which causes friction. When dissimilar materials rub together in this way they can create static electricity (the triboelectric series).
  2. A resin snooker ball rubbing against woolen cloth is a little like a plastic comb pulled through someone's hair - I'm sure you've tried this as a child; comb + tissue paper ;-)
  3. Ironically, a player often asks the referee to clean the cue and object ball just before an important shot - so the referee picks up a resin sphere, rubs it vigorously with cotton gloves (whilst wearing plastic or leather soled shoes), then places it carefully on a woolen cloth above a nice piece of slate, fully charged. Surely the referee is acting as a micro Van de Graaff generator! :)
  4. If a snooker ball accumulates a charge which is opposite (to some degree) to that of the chalk dust on the table (or the cloth it sits on), then the dust will leap onto the ball as soon as the referee places it back onto the table. Likewise from a cue tip to a cue ball, from cue ball to object ball (if differently charged) and so on, all around the table, throughout the match.

Problem Summary:

Chalk dust, static electricity, humidity and temperature have all been blamed for bad contacts and kicks in snooker. My idea, my suggestion, is that they are all partly to blame for this phenomenom for the reasons I've explained above. Other small particles of general dust (dandruff for example) and debris may also be contributing to the effect.

In my local club and other amateur clubs that I've played in, the snooker tables tend to have fairly robust cloths (I think so that they last longer and stand up to a bit of stick - no pun intended) which are fairly thick. I think with these kinds of 'slow' cloths the effects of chalk dust etc., are reduced since the balls tend to ride higher on the cloth/nap, above the various dusts and other debris which settles well below the nap. This may be one reason why kicks are more common during professional matches on 'fast' tables where the cloth/nap is thinner.

Testing for the Causes of Kicks in Snooker and Some Potential Solutions

In order to get to the bottom of this phenomenom I would like to suggest a couple of experiments which may help to prove or disprove some of the potential causes of kicks and bad contacts. One experiment to try to show whether chalk dust alone is the main cause, and a further experiment which will help to eliminate the influence of static electricity.

I don't personally have the time or resources to carry out these experiments or test the potential solutions, but it would be possible for a body like the World Snooker Association or the BBC (the cost would probably be a few thousand pounds). It could also be made into a small project which could be televised during a tournament as an aside, perhaps in collaboration with a few science students form The University of Sheffield :-)

Chalk as the Cause of Kicks - Experiment 1:

To discover whether snooker ball kicks are caused by chalk dust either on the balls or on the table surface, the following experiment could be conducted.

  1. The experiment would be carried out in a thoroughly cleaned room, without carpets, curtains, furniture (apart from metal or wooden chairs and table).
  2. A brand new match quality snooker table would be assembled in the room and set up ready for play. It would be important that no snooker would be played on the table at this stage and no chalk would be allowed into the room. Testing and set up would have to carried out with digital levels etc.
  3. The room would be thoroughly cleaned and vacuumed one more time.
  4. Two new and completely unused (untested and not contaminated with chalk) cues would be placed in the room along with a new set of balls, again completely untouched.
  5. Anti-static film sheets would be placed over the table and the cues and balls.
  6. Two professional players would be invited to take part in the experiment, and a date would be set. On the day of the experiment, these players would wear newly purchased clothes or suites to ensure that there would be no chalk remnants from previous games. Ideally, they would wear single piece lab or clean room coats, but this may too extreme :-)
  7. The experiment would consist of a set number of frames played without the use of chalk. I would think around ten to twenty frames would be enough to show some usable results. If there are no kicks or bad contacts (or almost none apart the odd jump caused by striking down on the ball etc.) during this initial experiment, then the indication would be that chalk dust is the main cause of the problem. Further, more comprehensive experiments could then be carried out to provide final proof.

The idea of this experiment is simple; if there are no kicks when chalk is eliminated from the game environment, then chalk must be the primary cause. Also, this would be an entertaining experiment since playing frames without chalk would produce some interesting shots! :-) It is perfectly possible to play without chalk, so the experiment is viable albeit probably lacking a little in side and screw shots.

Static Electricity as the Cause of Kicks - Experiment 2:

To discover whether snooker ball kicks are caused by static electricity either on the balls or on the table surface, the following experiment could be conducted.

  1. The experiment would be carried out in a thoroughly cleaned room, without carpets, curtains, furniture (apart from metal or wooden chairs and table).
  2. A brand new match quality snooker table would be partly assembled in the room. Before fitting the cloth, a highly conductive sheet would be placed over the slates. This conductive sheet could be a thin steel sheet (possibly stainless), a copper sheet, aluminium foil (industrial) or perhaps a metal or carbon fibre mesh.
  3. Several high quality cables would be attached to the conductive sheet and run out from the table to a central connection point.
  4. The snooker cloth would then be fitted over this conductive sheet. It would not need to be a full professional fitting, as long as it covered the playing surface and was securely attached at each side.
  5. The cables would then be attached in the first instance to a secure, high quality ground/earth connection (a mains water pipe or electrical junction box earth). Then later, in part two of the experiment, the cables would be attached to a charge generator which would apply a negative charge to the conductive sheet.
  6. As in the chalk experiment, ten to twenty frames of snooker would then be played (with chalk) by two professional players and the results observed. Again, if there were no kicks during the experiment, then it could be assumed that static electricity does indeed play a major role in the cause of this phenomemon. Once again, further more comprehensive experiments would be needed to obtsain final proof.

The idea behind this experiment is also simple but the method is a little more difficult to set up. If static electricity is to blame (or largely to blame) for kicks and bad contacts then eliminating it should cure the problem. However, eliminating static or minimizing its effect is a little more difficult than eliminating chalk.

My first idea is simply to ground or earth the table surface. This should equalise any charges on its surface (balls, hands, cues etc.), thus preventing any significant opposing charge build up which might cause kicks. The success of this idea depends on the thickness of the table cloth and its insulating properties; it may prove to be too much of barrier between the balls for example, and the conductive sheet.

My second idea is to charge the conductive sheet so that it attracts chalk dust particles and surface charges towards itself and away from the balls etc. This should provide a clean and uniformly charged playing surface. Of course, there's no way to know in advance what types of charges are building up on the balls and so on, so some measurements need to taken and some tests need to be carried out, prior to setting the experiment up.

Solution:

Depending on the results of the experiments above, a solution for preventing kicks could be devised as follows. If chalk is the main culprit, then measures could be taken to prevent its build up on balls and cloths etc. If static electricity is the main cause then again, measures could be taken to reduce its effects.

The following suggestions either individually or in combination would go some way towards providing a solution, assuming positive results were obtained from the experiments above.

  1. Players should try to keep their chalk dry during matches, keeping it out of their pockets if possible. Perhaps a thin silica gel pouch could be designed to line a player's waistcoat pocket for example, which would absorb moisture during a match. A small battery operated, heated tray could be designed to keep chalk warm and could be placed on the table during a match, and used when the other player is at the table.
  2. Anti-static cleaning spray could be used to wipe the balls in between frames. This would help to reduce the likelehood of static build-up. This along with anti-static cloths could also be used by players when wiping their hands and cues.
  3. Referees could be issued with anti-static gloves for wiping balls and could also wear anti-static shoes with conductive soles. All readily available. I don't know if these are already being used during professional matches.
  4. Snooker tables could be designed or retro-fitted with a number of anti-static features for example; a metal rod core drilled and run through each table leg and attached to a metal plate or foot at the floor end and interconnected around the table using various industry standard conductive meshes and other materials. This would help to 'suck' the static electricity away from the table to ground.
  5. A permanent conductive sheet or mesh could be designed into the table surface to allow for grounding or uniform charging. For example, the slate surface could be coated (chemically or by spraying etc.) with a conductive layer, or perhaps the table cloth could have a thin carbon fibre mesh woven into its base layer. If a uniform static (negative or positive) charge is required, it could be provided by a battery operted module attached to the underside of the table.
  6. A specially designed, lightweight vacuum cleaner could be designed for use during professional matches. A vacuum head equal to the width of the table's playing surface. It could be run along the table, with the nap, just once, in between each frame prior to repositioning the balls, in order to remove all the previous chalk dust from the table.
  7. I suspect that snooker chalk could be impregnated with a small precentage of anti-static material during manufacture to help prevent it from sticking to charged balls. This is a common process in the manufacture of packaging. This would also allow the manufacturers to charge a premium for this version of their product.

Uses / Applications:

Professional snooker matches, particularly if playing for significant prize money, or ranking points. Televised matches and tournaments, especially where high profile sponsorship is involved.

There may be one or two general products that could be developed to provide club level or even professional solutions to this problem, such as anti-static chalk or the chalk heater I mentioned above.

Resources:

Creative Commons Attribution 2.0Snooker-Saturn photo by kind courtesy of monkeywing

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