Materials made by cooling certain molten materials in such a manner that they do not crystallize but remain in an amorphous state, their viscosity increasing to such high values that, for all practical purposes, they are solid. Materials having this ability to cool without crystallizing are relatively rare, silica, SiO2, being the most common example. Although glasses can be made without silica, most commercially important glasses are based on it. The most important properties are viscosity; strength; index of refraction; dispersion; light transmission (both total and as a function of wavelength); corrosion resistance; and electrical properties.Chemically, most glasses are silicates. Silica by itself makes a good glass (fused silica), but its high melting point (1723°C or 3133°F) and its high viscosity in the liquid state make it difficult to melt and work. To lower the melting temperature of silica to a more convenient level, soda, Na2O, is added in the form of sodium carbonate or nitrate, for example. This has the desired effect, but unfortunately the resulting glass has no chemical durability and is soluble even in water (water glass). To overcome this problem, lime, CaO, is added to the glass to form the basic soda-lime-silica glass composition which is used for the bulk of common glass articles, such as bottles and sheet (window) glass. Although these are the main ingredients, commercial glass contains other oxides (aluminum and magnesium oxides) and ingredients to help in oxidizing, fining, or decolorizing the glass batch.---Sci-Tech Encyclopedia
Thirty-five years ago I had the daunting task helping my mother-in-law clean out her parent’s house. Amongst all the furnishings there were some favorite things I like. What are they? Items made of glass. I knew I couldn’t take it all to my house. And I had about two weeks to decide which items I wanted for myself and for our children. To learn more about the different types of glass sent me on an investigative search at our local library (the one in the theme two weeks ago). Searching through numerous books I learned there are cut, pressed, carnival, Tiffany and many more types of glass. Armed with the knowledge acquired I was able to make many good selections. I have been able to use the selected items during holidays and while entertaining.
I have chosen a mere four of my favorite pieces of glass selected to photograph for this week’s theme.