Team Members: Katie Gresh and David Leng
3rd Team Assignment: Stackable Bubbles
Flow visualization give insight to how flow phenomena operates in our surroundings. For this assignment, teams were tasked with photographing these phenomena. Team 2 consists of Sierra Castillo, David Leng, and Katie Gresh. The original plan for this assignment was to photograph fabrics flowing in the wind produced by a small fan. This apparatus was not working well for us, so we decided to experiment with some stackable bubbles provided by Katie Gresh. For my image, Christmas lights and fabrics were arranged at the bottom of our setup. We blew many bubbles and I waited until they had settled on these lights/fabrics. The imaged I captured is of one of these bubbles sticking to a bulb of the Christmas lights.
Our setup was very simple. A black poster board was used as a backdrop. On a lab desk, 2 strings of Christmas lights were arranged with Christmas colored fabrics. The photos were taken in the Integrated Teaching and Technology Lab (ITLL) at the University of Colorado Boulder. This lab has large windows which provided a lot of natural light, as well as soft overhead lighting. Figure 1 shows a schematic of the setup.
Figure 1: schematic of apparatus
The bubbles used for this experiment were not normal bubbles. They were Mr. Bubble’s Stackable Bubbles. If timed properly, one can actually catch these bubbles and they will not pop. Due to this, it is possible to stack the bubbles on top of each other, as seen in Figure 2 .
Figure 2: example of “stackable bubbles”
The team had some trouble determining the contents of the bubbles, as the packages are not labelled with ingredients. However, there are several do-it-yourself recipes to create a similar effect. One method involves mixing cornstarch with water and dish soap. Another method mixes glue and liquid starch. It is likely that the mixture in Mr. Bubble’s stackable bubbles is closer to the second method, as the solution smelled like glue during the cleanup process. The glue increases the surface tension of the bubble, which allows them to be touched without popping.
Another interesting aspect of these bubbles is the reflections and refractions of the light through them. Some of the reflections that you would expect to see on the left side of the image are actually seen on the right. The bubble appears to give a fish eye view of the lab. This is likely due to the bubble mimicking a translucent convex mirror . The light paths follow similar lines as those shown in Figure 3. This would explain why the reflections appear to be flipped.
Figure 3: path lines of light through a bubble
The lab had ample lighting at the time, both natural from the large windows and from the soft overhead lighting. The Christmas lights used also provided lighting for the camera.
|Field of View||~3”|
|Distance: Obj to Lens||~6”|
|Focal Length||52 mm|
|Exposure Time||1/200 sec|
The original and edited photographs are seen in Figure 3 and Figure 4 respectively.
Figure 4: original, unedited image
Figure 5: final, edited image
Overall, I am happy with the outcome of the team’s experiment. The bubbles were very fun to play with. If I had to change something about the image I would reduce the reflections of the lab on the bubble. Additionally, I would add more of the Christmas colors in the frame. More control of the lighting would help to control the reflections on the bubble. Also the image was a little dark and that would help with that. I like the soft lighting and the off black back ground. It gives the image a warm feeling of winter. I wish that I knew what the bubbles were made of to explore the physics further.