Balls
... physical characteristics of pool balls.
Balls... physical characteristics of pool balls.
Dr.
Dave's answers to frequently-asked questions (FAQs),
mostly from the BD
CCB and AZB
discussion forums
maintained for the book: The
Illustrated Principles of Pool and Billiards,
the DVD series: The Video Encyclopedia of Pool Shots (VEPS),
the DVD series: The Video Encyclopedia of Pool Practice (VEPP),
and the monthly Billiards
Digest "Illustrated Principles" instructional articles
Is there any rationale behind the choices for pool balls?
Every "solid" (balls 1-7) have a different color, and every "stripe" (balls 9-15) uses the same color as the corresponding "solid" (e.g., the 1-ball and 9-ball are both yellow).
If you arrange the balls in an 8-ball rack in a methodical way in color groupings, all sorts of numerical consistencies also arise.
from Patrick Johnson:
Three primary colors:
1 & 9 = Yellow (primary)
2 & 10 = Blue (primary)
3 & 11 = Red (primary)
Three secondary colors:
4 & 12 = Purple (blue+red)
5 & 13 = Orange (red+yellow)
6 & 14 = Green (yellow+blue)
One tertiary color:
7 & 15 = Maroon (purple+red)
Two all-or-nothing colors:
8 = Black
Cue = White
Does the size of the contact patch between the CB and OB vary with cut angle and speed, and does this affect how I should aim shots?
The CB and OB do compress a small amount during the extremely brief contact time, and this does create a "contact patch" that varies in shape and size with cut angle and speed, but the effect of this compression is very small. The compression does increase the cut angle slightly due to the contact patch compressing past the initial point of contact between the balls (when contact is first initiated), and this does tend to counteract the effect of cut-induced throw (CIT) a small amount, but the ball-compression effect is very small and can be neglected for all practical purposes.
How long are the CB and OB in contact during a collision?
Marlow did some experiments on this, and he reported numbers between 0.0001 and 0.0006 seconds. The balls don't stay in contact for very long.
What are pool balls made of?
Here are some good resources explaining the history and current state of pool ball materials:
Does Silicone spray help you get more draw and masse action on the CB?
Yes. In fact, some trick shot artists sometimes use Silicone spray to help them create some of the magical shots they can execute.
I describe and demonstrate the effects of Silicone spray in this video (starting at the 0:40 point):
NV B.40 - Masse-draw billiard (carom) trick shot from the movie "The Hustler"
Here's another (at the 0:35 point):
NV B.41 - Coriolis masse shot aiming method with a large-curve example
It works like a charm, but it does wear off over time as it wipes off onto the cloth. It also leaves slippery residue on your hands when you handle the CB.
Does the weight of the balls ever vary much, and does it have an effect?
The following video describes and demonstrates all effects related to using cue balls or object balls of different weights and sizes:
My February '02 and March '02 BD articles also cover ball-weight-difference effects in detail.
Generally, with older balls, the cue ball (CB) will be slightly smaller and lighter than the object balls (OBs) because it takes more abuse and wears faster as a result. However, if a new CB is used with an older set of OBs, the CB will be slightly heavier because only the OBs will have wear. On many coin-operated tables in bars (i.e., "bar boxes"), the CB is often heavier and/or larger than the other balls to help the ball-return mechanism distinguish the CB from the others.
When the CB is heavier, it is easier to follow and tougher to draw. With a cut shot, the CB will go forward of the tangent line; and with a stop shot, the CB will drift forward some. A heavier CB will also squirt slightly less.
When the CB is lighter, it is easier to draw the CB and tougher to follow. With a cut shot, the CB will pull back from the tangent line; also, with a stop shot, the CB will bounce back some. A lighter CB will also squirt slightly more.
When the CB is smaller or larger, the contact point on the OB will not be at the equator, the balls will also tend to hop a little, especially with faster speed. With cut shots, the cut angle will also be off slightly (as with jump shot over-cut), but this is an extremely small effect.
Worn OBs will also not rack as well as new high-quality balls. Slight mismatches in size and non-spherical shape (due to non-uniform wear) will result in less-tight racks and poor break action (bad spread, more clusters, fewer balls made).