Some notes on ball-spinning, from some posts by Steven M. Salberg, with help from Andrew Conway, Mark Olson, Andy Arhelger, and others.
The best spinning ball I have found is the Hedstrom Dura Glow 12 available in the US from Toys R US. It should be under inflated, so that your fingernail makes a small indentation when the ball rests on it.
I prefer vinyl balls, but some of the great ball spinners prefer rubber. Francis Brunn takes a large rubber Zoomer ball, sands it smooth, floats it in water then sands the heavy side until the ball is perfectly balanced. Rubber balls require frequent washing with a solvent such as acetone and/or an abrasive to prevent the grease from your skin making the rubber slick...
...I agree that the Hedstrom Dura Glow series is a very good ball. I use them for part of my spinning act. They come in many different sizes: I've used 9", 12" and 15". They have a very tacky surface and hold up very well to the digging from the fingernail and come in many bright colors. However, the best ball I've ever used is the new one from Dubé. They have everything I need in a spinning ball: Tacky, Heavy, Strong and easily in/deflated. I use the ones painted like a soccer ball.
I learned to make rubber balls [like mentioned above] from Lotte Brunn (Francis' sister) and was given one of hers as a present. These balls are good and heavy but suffer from a major drawback. If you spin on your nail-tip as opposed to your finger-tip skin, the ball gets holes dug into it. Lotte and some others say to plug the hole with rubber patches, but that's just too much trouble for me.
Mark Nizer uses volley balls and digs holes in his too. He solves the problem by adjusting the ball's center of gravity by taping coins onto it to move the point of spin away from the holes. After a while the ball gets to look like a mini asteroid with pock marks all over it.
Here's some basic stuff: I originally learned to spin balls by taking 2 or 3 beach balls (the kind found at every pool: multicolored panels with a poke-in nipple at the top (I won't say it). Cut the nipple off of 1 and stuff the other inside of it (or cut 2 and stuff 2 inside) so that the inner, or last one inside still has an inflation nipple. when you blow the inner one up, it will be heavy enough to catch without much bouncing off the finger (the biggest problem at first). Whichever balls you use (Heavy, soft, tacky playground balls, or beach balls) practice with it very under-inflated as it makes the catch much easier.
Find the heavy point of your ball: Put it in a bowl of water and mark the spot that ends up on the bottom with some sort of marking pen or paint about the size of a nickel (sorry UKers, don't know how big a shilling is :-) try about the width of your thumbnail).
To start: Before you can catch a spinning ball on your fingertip you must learn to spin the ball. It's not that easy. There are two spins: Inside (counterclockwise looking down from above) and Outside (or Reverse) (clockwise from above). There are plenty of arguments as to which is easier. You decide for yourself but don't ignore either one as they are both needed to do various tricks. Diaboloers know about precession and it comes into play in ball spinning... more in later postings.
To spin the ball in a flat plane (the ball should spin with it's equator parallel to the floor) you should hold the ball at eye level in front of the shoulder elbow out, palm up with the dot in your palm (as if you're carrying a tray) you should be looking at your thumb. Now spin the ball in the Inside direction (as if you are turning a screw into the ceiling). Spin the ball up into the air about 6-12 inches and just catch it again (don't try to catch it on your finger yet, I'm trying to teach you something). Did it spin flat? Did it spin fast? Did it hit the cat... probably.
If you marked the ball you will see the point of spin on the bottom of the ball (the south pole). That is where you are going to aim your finger. To make the spot spin at the very bottom, you'll have to learn where to position the dot in your palm when you learn how you spin the ball.
When you've got the ball spinning (1) flat, (2) moderately fast, (3) not flying up into the air 3 feet... you can try a catch.
When you spin the ball it flies up into the air some 6-12 inches. The ball peaks at a point where it is motionless for a split second (apogee?). That would be the PERFECT point to catch it. In actuality, we catch it on the way down, but well before it has any chance to speed up its descent. If you catch it too far below apogee, it will probably bounce. Also, wherever you catch it, you have to *give* with it. What I mean is you have to continue the motion of the ball falling to cushion the catch... when the ball lands on your fingertip - continue dropping your hand along the path the ball was taking (sort of like you were catching an egg.
Andy Arhelger offers more advice:
To learn this get a big rubber ball from Toys-R-Us. The bigger the better. Let most of the air out so the ball doesn't bounce and when you put it on your finger you make an indentation in the bottom that goes in an inch or more.
The spin: If you are right handed hold the ball in your right hand and spin counterclockwise (to the outside of your body). You will use your wrist for the spin but make sure your forearm is also part of the spin. You will tend to throw the ball out away from you when you spin it which you need to get under control. Also hold your palm flat with the fingers pointing back, like the waiters do when then carry trays. Don't let your hand get to far from your body when you spin. (Close in to your ear.)
Left handed spins follow the same rules except the go clockwise.
With practice you can keep the axis of the spin vertical. This is important for a good catch.
You need a faster spin for tricks and the catch is easier, but you will also tend to throw crooked if you try to put too much into the spin. Practice helps here.
The catch: Try to catch the ball on the axis. Drop your hand lightly as you catch to prevent any bounce. The ball should recenter itself with your finger as the new axis if you were not too far off. I catch the ball on my index finger with my finger tipped slightly so it lands on my nail rather than the skin. Lots of spinning on your finger tips can really make them sore. (Is that called ball burn, as opposed to rope burn)
Keeping it there: The ball will pretty much stay by itself once it lands correctly. If you then try to move the ball around you will need to compensate slightly by moving your finger under the ball. This also comes with practice.
More: Once you get good with the deflated ball (maybe a couple of days) you can add more air to the ball. If it gets to the point where it is bouncy then you really need to watch it during the catch so it doesn't bounce off your finger. Then try other balls. Bigger ones are easier. A soccer ball works pretty good but the seams may get in the way. My hand is not quite big enough to spin a basketball with one hand so I need to use both hands. Basketballs also are heavy and they can hurt your finger after a short time.
Many (if not most) full-time performers spin the ball on the skin of the fingertip with their nails trimmed back. They develop hard callouses and the ball seems to spin fine. I cannot afford to have callouses on my fingertips. A Chiropractor's fingers are his instruments (so why do I pass american clubs? Everybody has to have his priorities straight :-)).
I keep the fingernails of my index and middle fingers trimmed to a subtle rounded point (anything more exaggerated than "subtle" would most certainly cause some consternation in some patients' minds :-)). Another drawback of spinning on nails is if you break one (and that *does* happen). That is why I keep the middle fingernails in shape too (I've learned every trick on both the index *and* the middle fingers... just in case). When I am performing I get my spinning nails "linen wrapped" which makes them VERY strong...
...Greg Hosfeild (sp?) glues little plastic things to the back of his fingernails to spin with when he's in performance. I believe he uses a glue that can be dissolved with fingernail polish remover. He mostly spins frisbees, but I'm sure the idea would apply to balls. They are not noticeable from the audience...
...There was a program on TV, several months ago, that profiled frisbees and frisbee people. One of the frisbee passers would glue a fake fingernail to his index finger (using superglue!!!). He would catch the frisbee on this 'fingernail' and could maintain quite a spin. He would also coat the interior surface of the frisbee with PAM (a sort of spray on vegetable oil used primarily for cooking) to reduce the friction.
Occasionally, if there is a great deal of friction between my fingernail and the ball, I will wipe my fingernail on the area behind my earlobe, this provides just enough lubrication to reduce the friction between the fingernail and the ball...
Place the top ball on the north pole of the bottom ball, and give it a little spin as you put it on. As the top ball picks up spin from the bottom ball the balance changes from a gyroscope balance to something closer to a stick balance. You'll just have to practice this one.
A good way to finish is to throw both in the air, catch the top ball, let the bottom ball bounce once and catch it in a balance on top of the former top ball. (Balancing one large ball on another is easier than it looks.)