As we discussed with antispin rubbers, there are several factors involved in how a particular long pimpled rubber works. Each long-pimpled rubber uses these factors differently, which is why no two long-pimpled rubbers play exactly the same way. The factors involved are listed below. Please keep in mind that this is my theory about long pimples, so I'm not claiming to be the last word on the subject.
Please keep in mind that in the items discussed below, the amount of spin we are talking about is much less than for inverted rubbers, but it is still significant.
(1) Amount of Grip of the Top of the Pimples.
All long pimpled rubbers have much less grip than normal rubbers, but this does not mean that they all have no grip. There is actually quite a difference in grips between different long-pimpled rubbers. The more grip they have, the more the player will be able to change the spin that you have put on the ball. Some long pimples have smooth, almost glassy pimple tops that do not grip the ball at all, while others have rougher pimple tops that will grip more, and yet others have a smooth pimple top that grips.
(2) Amount of Grip of the Sides of the Pimples
The sides of the pimples can vary in the same way as the tops, with similar effects. Bear in mind that the sides do not have to be the same as the tops! The importance of this fact will be clearer after reading the next point below.
(3) Softness of the Pimples
The softer the pimples, the more they will tend to bend when the ball is hit, and the more the sides of the pimples will be able to touch and affect the ball. Stiff pimples will require more force before they bend, but once they do, they may bend quite a lot! A player using softer pimples will be able to produce more spin variation that a player using stiff pimples, provided that the sides of the pimples have some grip.
(4) Width, Density, and Shape of the Pimples
The wider the pimples, the less they will tend to bend, and thus the less the sides of the pimples will touch the ball. The more dense the pimples, the more contact can be made with the ball and the more the rubber will be able to affect the spin. The shape of the pimples is a bit more difficult to figure out. Most pimples are the same width at the bottom and the top, but not all. The pimples that I used to use were actually narrow at the bottom and wide at the top, like a funnel or ice cream cone. I believe that this tends to make the tops of the pimples get more contact with the ball while the sides of the pimples get less. Whether this is true, and whether it is even a significant difference is open to debate (I liked them though!). I assume the reverse would be true for a long pimpled rubber with a wide base and narrow top.
(5) Thickness and Hardness of the Sponge
The thicker and softer the sponge, the more the pimples will sink into the sponge when the ball is hit, and the more pimples will be able to touch the ball to generate spin. The sponge will also help catapult the ball back from the bat, adding some speed to the ball. Long pimpled rubbers without sponge will tend not to have this catapult effect, and will be slower than their sponge counterparts.
(6) Speed of the Rubber
The faster the overall rubber, the less time the ball will stay on the rubber and the less opportunity to spin the ball. I think that there have been studies done that indicate that the speed of the rubber does not affect the dwell time, but this is my gut feel about the effect of rubber speed.
(7) Speed Glue
Speed glue softens the sponge, allowing the pimples to sink into the sponge and allowing more pimples to touch the ball, as in (5) above. It also increases the catapult effect, increasing the speed of the return.
(8) The Type of Stroke Used
The type of stroke used is very important with long pimpled rubber, much more so than for anti-spin rubbers. I don't think I can do this factor justice in a short paragraph, so I'll deal with it later in the article on a page of its own
(9) Speed and Bounce of the Return
The effect of the long pimples on the spin of the ball is not the only problem that you will face. Compared to a stroke with an ordinary rubber, the amount of speed on the ball will be less with the same stroke made by an long pimpled rubber. A thicker, harder sponge will tend to return the ball faster, but it will still not be anywhere near as fast as a normal rubber. A speed-glued long pimpled rubber might just about get there, though. In addition, the bounce of the ball off the table will also be different, due to the difference in spin and speed applied by the long pimpled rubber.
All of these factors will affect the amount that your opponent can change your spin. Bear in mind that if you spin the ball and your opponent does not change your spin, the ball will keep spinning in the same way but it's overall motion will be in the other direction, so if you hit a topspin it will come back to you as backspin, and if you hit a backspin it will come back to you as topspin. This is true regardless of what rubber your opponent is using, it is just easier to do with long pimples. (Think of a chopper chopping a loop, for example. The spin on the ball is always in the same direction, but it is coming to the chopper as topspin, and to the looper as backspin.)
Next: How Do Long Pimples Work in Practice?