Posts Tagged ‘temperature’
Video: They Sure Don’t Make Pyrex Like They Used To
A change to heat-resistant glass has had explosive effects
Ordinary glass shatters if it’s heated too quickly: Pour boiling water into a common flintglass tumbler, and it’s likely to fall apart seconds later. The glass on the inside expands when it gets hot, putting stress on the cold glass on the outside. When the stress gets too great, it cracks.
Pyrex, which originally was always borosilicate glass, solved this problem by adding boron to the silica (quartz), the main ingredient in all glass. Boron changes the atomic structure of glass so it stays roughly the same size regardless of its temperature. Little thermal expansion means little stress. Thus borosilicate glass withstands heat not because it’s stronger, but because it doesn’t need to be stronger.
When World Kitchen took over the Pyrex brand, it started making more products out of prestressed soda-lime glass instead of borosilicate. With pre-stressed, or tempered, glass, the surface is under compression from forces inside the glass. It is stronger than borosilicate glass, but when it’s heated, it still expands as much as ordinary glass does. It doesn’t shatter immediately, because the expansion first acts only to release some of the built-in stress. But only up to a point.
One unfortunate use of Pyrex is cooking crack cocaine, which involves a container of water undergoing a rapid temperature change when the drug is converted from powder form. That process creates more stress than soda-lime glass can withstand, so an entire underground industry was forced to switch from measuring cups purchased at Walmart to test tubes and beakers stolen from labs. Which just goes to show, if you think you know all the consequences of your decisions today, you’re probably wrong.
A Video Game Controller that Stimulates with Hot and Cold Sensations
An experimental new video game controller just revealed at this week’s SIGGRAPH conference includes a pair of thermoelectric panels on each side of a controller. Those surfaces heat or cool rapidly in reflection of what’s happening in the game, offering players a new sensory connection to what’s happening on the screen.
The controller temperature doesn’t swing wildly – less than 10 degrees in either direction in just five seconds – but apparently a small sensation is all that’s needed to add a rich layer of sensory experience to a virtual reality environment. No word on whether any major console makers are eyeballing such technology, but the idea is pretty cool. After all, remember how thrilling it was when our gaming peripherals started vibrating?
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