Making the Dry Ice on a Hoop Video
Here are some images from the recording session for the Dry ice sliding on a circular hoop video.
The hoop was formed by clamping a 6" wide strip of sheet metal to the rim of the bike wheel. This smooth, wide surface reduced friction and ensured that the puck did not fall off the edge of the hoop as it slid.
The bike wheel was clamped on a lab table. The black background was ideal for increasing contrast to make it clearly visible when the puck leaves the surface.
The silver aluminum reflector aimed at the top of the hoop warmed the surface of the hoop to increase the rate of sublimation, hopefully reducing sliding friction.
Two halogen spots illuminate the puck, while the softbox lights the wheel. The camera was aimed parallel to the hoop surface at the height where the puck lost contact with the hoop. This makes it easier to see when the puck loses contact with the surface.
The dry ice pucks were cut out of a slab of dry ice. A copper hoop was heated with a plumbing torch, then used to cut/melt through the dry ice slab.
The cylinder was split into two smaller disks, which slide smoothly along the hoop.