Probably the best article I've seen on "squirt", if you understand, or get by, the math is this one:
http://www.sfbilliards.com/shepard_squirt.pdf
Here are the answers he comes up with after all the math and experiments:
"Summary: With the detailed discussion given above for squirt, several of the questions posed in the beginning can be answered.
• How can squirt be minimized? By reducing the tip offset or by using a cue stick with a small endmass.
• Does shaft flexibility affect squirt? No, not directly. Shaft flexibility may affect the endmass and thereby affect squirt indirectly, but this is probably a relatively minor effect. This means that the player is able to choose a cue with a desired amount of shaft flexibility for other reasons, without having to compromise the squirt characteristics.
• Does tip curvature affect squirt? No, not according to the above analysis, except for the fact that the tip curvature affects the actual tip offset for a given shaft offset. However, there are data at the Predator web site that suggests that a rounder tip (i.e. a dime radius compared to the larger nickel radius) reduces squirt.
• Does squirt depend on shot speed? No, not directly. Shot speed might affect the endmass, but this is probably a relatively minor effect. The observation that different aiming is required for different shot speeds, particularly on longer shots, is probably due to cue ball swerve, not to squirt.
• Does squirt depend on the cue stick weight? Yes, but only when it affects the endmass. Weight added more than about 10″ away from the tip apparently has little effect. This means that the player is free to choose stick weight for other reasons without compromising squirt characteristics.
• Does squirt depend on the stick balance point? Yes, according to the rigid cone approximation, but only because it has a small effect on the endmass.
• Do ivory or brass ferrules have more squirt than synthetic materials? If so, it is primarily because of the density of the material and the resulting effect on the 18 endmass. It appears unlikely that the hardness or other physical characteristics affect directly the squirt. However, a thick brass ferrule will probably have more squirt than a thin brass ferrule. Also, some ferrules are attached to the shaft with a metal screw or stud; these cues probably have larger squirt than an otherwise equivalent cue with a standard wood tenon.
• Does the tip diameter affect squirt? Yes, because smaller tips will have smaller endmass, all other things being equal. This trend is predicted by the rigid cone model. However, there are other ways to reduce endmass than by using a small tip diameter, such as the approach used by the Predator design.
• Does tip hardness affect squirt? No, not according to the above analysis. This also suggests that the tip-ball contact time, which is related to tip hardness, does not directly affect squirt, but this has not been proven independently, and it is possible that contact time does play at least a minor role in determining the effective endmass through speed-of-sound mechanisms. To the extent that tip hardness is independent of squirt, this means that the player is free to choose tip hardness based on personal preference without compromising the squirt characteristics.
• Is squirt caused by the tip slipping on the ball? No, squirt occurs even when the tip does not slip. The tip does not slip on normal shots.
• Are there any stroke techniques that can be used to minimize squirt? No, not unless the technique somehow reduces the tip offset, in which case the same shot could have been achieved simply by stroking normally and using the smaller tip offset in the first place.
• Is it better to use an open bridge than a closed bridge? It is possible that a tight closed bridge might increase the effective endmass, and thereby increase squirt, but this is probably a very minor effect.
• For a given cue stick, will snooker balls squirt more than pool balls, and will carom balls squirt less? There are two separate effects, mass and ball diameter. Due to the ball/tip mass ratio, the lighter snooker balls will tend to squirt more than pool balls, and the heavier carom balls will tend to squirt less. Futhermore, the stick pivot point depends on the ball radius, so, for a given relative tip offset and ball/tip mass ratio, the larger balls will tend to have longer stick pivot points.
• If I use a low-squirt cue, must I suffer from excessive or sensitive sidespin? All other things being equal, high-squirt cues will appear to get slightly less spin (and speed) than a low-squirt cue for a given tip offset, but this is a very minor effect, smaller, for example, than the differences in tip curvature between two tips might affect the amount of sidespin.
• Does the amount of shaft bend, buckle, or vibration affect squirt? No, the shaft is set into motion as the tip strikes the ball, but the actual bending and/or buckling occurs after the short tip-ball contact time. If the ball has already separated from the tip before the bending occurs, then the bending and buckling can have no effect on the ball.
• Must I trust the advertising of the cue makers to tell me how much squirt a stick will have? No, the aim-and-pivot squirt test is a reliable way to determine squirt, it requires no special equipment, and with a little practice, it can be performed by anyone with a reasonably straight stroke.
• What is the optimal squirt characteristics for a break cue? The stick pivot point should be at the bridge length. For most players, this will be typically in the 14″ to 16″ range.
With these answers in mind, there are still many details that are not understood at present regarding squirt. A more detailed understanding of endmass appears to be the most important. How exactly does the mass distribution along the shaft contribute to the observed effective endmass? And even if a complete and correct understanding of endmass and squirt were known, there would be still the subjective challenge of choosing a cue stick with the optimal amount of squirt for each player.
Postscript: This document is a first step at collecting together information and ideas related to squirt, it is not the final answer to this interesting and practically important topic. This document will evolve in the future in order to report and describe new developments, new explanations, and new squirt data. Comments and corrections should be sent to the author at email://shepard@tcg.anl.gov."
