Marbles (not opaque)
bowl of ice water
Place the marbles in a dry frying pan (no oil!) and cook on high for 15-20 minutes, keeping the marbles rolling constantly. Although you may be skittish like me and have that nagging vision of them exploding into evil, molten glass shrapnel- don't fear, the glass is pretty stable at high temps.
Once they've been heated for about 15 minutes, carefully spoon one marble out of the frying pan and drop it into to bowl of ice water. The second it hits the cold water the inside of the marble should crackle, while the outside should remain smooth and round. If the first marble only has a crack or two in it, continue cooking the remaining marbles for another 5-10 minutes and try again.
After they've been allowed to cool for a minute or so, removed the marbles and place them on a towel to dry. Don't be surprised if they are foggy for a few full minutes no matter how much you wipe them.
We used clear marbles, but by using different colors and/or swirls you'll get different effects. The only thing that won't work is opaque marbles, as the crackle won't show through. They are somewhat fragile after this process and may break if dropped onto a hard surface, so please don't allow children (human or fur-children) to have access to them. They make a great accent to a clear flower vase, a gazing ball in a terrarium, and can be used for jewelry.
Spread the wires so that they are evenly covering the front of what will be the bead cage. All of the ends should be headed in the exact opposite direction, e.g. the front middle should end up in the back middle position, the front left should end up in the back right position... etc.