Part of our mission at The Corning Museum of Glass is to tell the world about glass. One of the ways we do this is outreach to specialized communities. At The Studio, we have many such programs: Road Scholars, Veterans Day Glassblowing, Beads of Courage, Expanding Horizons, art classes for Corning’s alternative high school, participation in a local Maker’s Faire, to name a few. Working with specialty groups is fulfilling for us as instructors because we can really tailor teachings around others’ needs.
The Rakow Research Library staff aims to create a comprehensive collection that tells the story of glass. As you might imagine, in building such an inclusive collection, we come across materials in all shapes, sizes, and conditions. Occasionally, some of these materials are in rough shape, but if they are unique or important to glass scholarship we will acquire and care for them knowing the value the item will have for researchers.
I recently encountered such an occasion when these catalogs were offered to the Library:
There’s no record of how it happened, but sometime in the past 132 years, this glass model of a sea star was broken and lost one of its arms. The model originally had five solid glass arms which were glued into corresponding openings in a hollow central body. Two double rows of tiny glass feelers are glued onto the sides of each arm. The colorless glass was expertly painted to accurately portray the creature. The model is broken in various places, three of the arms have become detached from the body and one of those is now lost.
We are making Cartesian divers at our Spring Break MakerSpace next week. Come join us and make your own!
What is a Cartesian diver?
A Cartesian diver is an object used to demonstrate the relationship between density and buoyancy. Density describes how much matter is in a certain volume. Imagine filling two measuring cups, one with vegetable oil and the other with water. Now imagine placing those cups on a kitchen scale. You would find that one cup of vegetable oil has a mass of 223 grams and one cup of water has a mass of 240 grams. Vegetable oil has less matter in one cup than water, so vegetable oil is less dense than water. Buoyancy is the ability of an object to float in water. If you poured the vegetable oil and water into the same container, the vegetable oil would be buoyant and float on the water. Cartesian divers are interesting because their density and buoyancy can be changed at will, which means they can float or sink (hence Cartesian “diver”).
Cartesian divers are thought to be named for Rene Descartes. They are known by many different names, including: Cartesian devils, water devils, water dancers, and bottle imps.
How does it work?
Before the demonstration begins, the Cartesian diver is floating in the sealed cylinder of water. The diver is less dense than the water. Then, pressure is applied to the vessel containing the Cartesian diver by pressing down on a flexible membrane at the top. As pressure increases, the gas within the Cartesian diver is compressed, and the diver’s density increases to the point that is no longer able to float in the water. Thus, the diver lives up to its name and sinks to the bottom. However, when the pressure is released, the gas expands to its original volume and the Cartesian diver becomes a Cartesian floater!