The liquid is corn syrup and food coloring so it moves slow. If you move the beaker side to side the goo arcs nicely. I had a bunch of hands helping with this one and after many tries it worked out nice. Just got lucky really but I'm real happy with it.
I love your photographs but I wish you experimented with background colors more. looking through your (huge huge huge) collection I noticed most of the color was up front in the props and it'd be interesting to see some background flavor.