Teachers, do you struggle for words when it comes time to work on developing a student's spiccato? I know I do, but today I must have said it just right because in no time at all I had one of my 'peanuts' doing a beautiful slow spiccato. I start with a slow eighth-note spiccato, about 132 to the eighth note on the metronome. I explain that you can't "make" your bow bounce, instead you have to "let" it bounce. Your wrist has to be a little higher than your elbow. Your approach to the stroke is horizontal rather than vertical (so many think bouncing is an up and down thing rather than a side to side thing...). You gently drop the bow from slightly above the string. A down bow is a drop-pull and an up bow is a drop-push. This is usually where my explanation stops, and then we keep trying it. Modifications on my part follow, they keep trying, etc.
However, today I started talking about feeling the weight of the tip of the bow and it just did the trick. It makes me so happy when a concept is understood, and I think spiccato is one of the more difficult ones.