Sunday, February 10, 2008
Well, I had tea. There ya go.
But hey - I can make this relevant and interesting to any glass curious minds:
Ever wonder why Pyrex brand glass can hold boiling water and sit in a hot oven? Pyrex is one company (of many) that produce what is technically known as Borosilicate Glass, "boro" for short. Boro is especially stress resistant. Most importantly boro can take thermal shock without breaking - and this is what makes it so special.
Regular artistic glass (soda-lime, crystal, moretti Italian glass, etc...) all are very temperature sensitive. Thermal shock is more violent to glass than blunt trauma. Glass is hot and molten up over 2000degrees Fahrenheit - in that range between frozen glass at room temperature and hot molten glass there are a few key temperatures. There is a specific temp. that I call "the stress point" - this is when the glass is most likely to express shock (ie break). Think about a person, every person has a breaking point, a button so-to-speak. Glass is no different, each glass has a temperature that will manifest cracks where tension was held.
Boro has a stress point around 950degrees Fahrenheit. All other types of glass have a stress point around 150degrees Fahrenheit. This is why if you put a piece of art glass in the oven, you will probably break it. Pour boiling water into a glass vase and it will shatter, however a piece of boro (like the Pyrex tea cup in the pictures) can take all sorts of high temperatures. Nothing we do in the kitchen will get the glass up around 950degrees, so we can use the Pyrex glass to cook without worrying about cracks and breaking.