Jets at Home
You can recreate the granular jet in your kitchen using common household items. All you need is a cup, a small ball, such as a marble or even a BB and a dry, fine grained powder. Be careful selecting your powder, since many powders (like flour or powdered sugar) clump together due to humidity in the air. We found that a freshly opened package of baking soda worked very well. (I doubt the brand matters that much).
The trick to getting a jet is to start with a very loosely packed bed of grains. In our experiments we obtained this loose packing by bubbling air through the bottom of the bed then turning the air off before the drop. You can get this loose packing yourself by quickly pouring the powder into your cup.
You only have to release the ball from one or two feet above the surface to get a nice jet. The jet is suppressed if the ball hits too close to the walls of the container, so aim for the center and let it go.
The jet is small and quick, but if you look carefully (don't blink) you will see a nice little granular jet.
Have fun experimenting with other powders and projectiles and let us know what works out. Feel free to email us with questions or comments at