Method

Triggering, Timing, and Imaging Methods:  

Video clips of the splashes were obtained with both the side lighting and backlighting techniques. During trials involving side lighting, the camera was set with an f-stop of 2.5. However, backlighting was primarily used throughout the course of this experiment, and required an f-stop of 6.  After the first few trials, only backlighting was used as a light source.  This is because backlighting allows for more detail in ripples and offers more contrast between the liquids.

The high-speed motion picture camera was always at maximum zoom, and the distance it was placed from the graduated cylinder was used to vary the amount of the splash seen in the frame. The frames per second and the shutter speed were recorded on the video clip, and often varied. The recording rate we used was based on trial and error. Because the splashes were occurring at such high speeds, we wanted to use the fastest frame rate possible without loosing image quality. Many of our clips were made at 1000 frames per second because it offered both speed and resolution. 

During the experiment, one of us controlled the video camera, and the other controlled the burette. To take the high-speed video clips, recording was started slightly before the drop was released from the burette by pushing the “record” button on the camera controls. Timing of the initiation of the recording and the drop’s fall was coordinated by counting “1, 2, 3, ready, drop.” Recording was stopped after the drop splashed by pushing the “stop” button. After reviewing the video clip on the high-speed motion picture camera, the clip was played back at both 30 frames per second and 10 frames per second to a recording Sony DRV-900. Selected clips were compressed for online delivery. 

Overall Plan:
            The design of the experiment was based on three fluid concepts. The first was that milk and petroleum ether are not soluble in each other. This allowed for a splash to proceed without the chance that the two fluids would mix. The second concept was that milk was opaque, while petroleum ether was clear. The milk splashes would easily be seen on film because the petroleum ether would allow imaging of only the milk drop. The third concept was that milk is denser than petroleum ether, meaning that the drop of milk would sink after each splash, allowing for a clear petroleum ether layer for imaging. These three combined concepts created a unique design that led to this in depth study of dual liquid splashes via high speed video. 

           Another design characteristic of the experiment was the use of backlighting to create better videos, as the glare caused by the studio light was a nuisance. The use of a clear graduated cylinder rather than the standard lined cylinder offered a clear view of the splash. Food coloring was  used with water splashes to allow for the differentiation of water from the petroleum ether. These design features, along with the properties of the liquids, produced an interesting and successful experiment.