posted on March 2, 2006 07:21:16 PM new
I have a china cabinet that supposedly belonged to my great granmother. That would have put it at approx 150 years old I think. It is very daintly made of mahogany and glass. The glass has a slight tint to it. Can you tell me why? Just curious. It reminds me of those old glass bottles I used to see all the time with that tint of pink or blue. This one is a slight blue color
posted on March 2, 2006 11:29:40 PM new
Paloma: We've had lots of experience with old bottles turning purple, at all stages of that color change, and I think you might see a little blue in some of them at first; pink is more common when they first begin to turn color.
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posted on March 3, 2006 12:10:04 AM new
paloma91 - Find out more about glass here http://en.wikipedia.org/wiki/Glass . I own a piece of property I inherited from my father when he passed away years ago. The house is about 200 years old and slowly sinking into the ground and is known locally as a haunted house (yes it's one of those eye sores that's sinking and breaking in half but it's a home for the local racoons and snakes). Most all of the panes of glass in the windows of the house are the original vintage glass. Very wavy and all show a rainbow or color change when you look through them. In the old day's they used many different additives to get the best glass proporties that could be made with the technology they had. Today's high tech glass production has eliminated most of the bad quality's that were found in old glass like the color tint's.
Glass ingredients
Pure silica (SiO2) has a melting point of about 2000 °C (3600 °F), and while it can be made into glass for special applications (see fused quartz), two other substances are always added to common glass to simplify processing. One is soda (sodium carbonate Na2CO3), or potash, the equivalent potassium compound, which lowers the melting point to about 1000 °C (1800 °F). However, the soda makes the glass water-soluble, which is obviously undesirable, so lime (calcium oxide, CaO) is the third component, added to restore insolubility. The resulting glass contains about 70% silica and is called a soda-lime glass. Soda-lime glasses account for about 90% of manufactured glass.
As well as soda and lime, most common glass has other ingredients added to change its properties. Lead glass, such as lead crystal or flint glass, is more 'brilliant' because the increased refractive index causes noticeably more "sparkles", while boron may be added to change the thermal and electrical properties, as in Pyrex. Adding barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion, and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern glasses. Large amounts of iron are used in glass that absorbs infrared energy, such as heat absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs UV wavelengths (biologically damaging ionizing radiation).
Glass as a polymer
An innovative way for making glass involves preparation by polymerization. Putting in additives that modify the properties of glass is problematic, because the high temperature of preparation destroys most of them. By polymerizing glass it is possible to embed active molecules, such as enzymes, to add a new level of functionality to the glass vessels. Sol gel is a good example of glass prepared in this way.
Colours
Metallic additives in the glass mix can produce a variety of colours. Here cobalt has been added to produce a bluish coloured decorative glass.
Metals and metal oxides are added to glass during its manufacture to change its colour. Manganese can be added in small amounts to remove the green tint lent by iron, or in higher concentrations to give glass an amethyst colour. Like manganese, selenium can be used in small concentrations to decolorize glass, or in higher concentrations to impart a reddish colour. Small concentrations of cobalt (0.025 to 0.1%) yield blue glass. Tin oxide with antimony and arsenic oxides produce an opaque white glass, first used in Venice to produce an imitation porcelain. 2 to 3% of copper oxide produces a turquoise colour. Pure metallic copper produces a very dark red, opaque glass, which is sometimes used as a substitute for gold in the production of ruby-coloured glass. Nickel, depending on the concentration, produces blue, or violet, or even black glass. Adding titanium produces yellowish-brown glass. Metallic gold, in very small concentrations (around 0.001%), produces a rich ruby-coloured glass, while lower concentrations produces a less intense red, often marketed as "cranberry". Uranium (0.1 to 2%) can be added to give glass a fluorescent yellow or green colour. Uranium glass is typically not radioactive enough to be dangerous, but if ground into a powder, such as by polishing with sandpaper, and inhaled, it can be carcinogenic. Silver compounds (notably silver nitrate) can produce a range of colors from orange-red to yellow. The way the glass is heated and cooled can significantly affect the colors produced by these compounds. The chemistry involved is complex and not well understood. New coloured glasses are frequently discovered.
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. - Albert Einstein
[ edited by mikes4x4andtruckrepair on Mar 3, 2006 12:13 AM ]
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. - Albert Einstein
[ edited by mikes4x4andtruckrepair on Mar 3, 2006 12:13 AM ]