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Topic: Crown glass process

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	Glass - Wikipedia, the free encyclopedia
		That the Phoenicians used glass as a glaze for pottery was known as early as 3000 BC.
		Drinking glasses, bowls, and bottles are often made of glass, as are light bulbs, mirrors, the picture tubes of computer monitors and televisions, and windows.
		Glass is generally treated as an amorphous solid rather than a liquid, though different views can be justified since characterizing glass as either 'solid' or 'liquid' is not an entirely straightforward matter [2].
	en.wikipedia.org /wiki/Glass (3925 words)

	Glass - Biocrawler (Site not responding. Last check: 2007-10-22)
		In the 1920s a new mold-etch process was invented, in which art was etched directly into the mold, so that each cast piece emerged from the mold with the image already on the surface of the glass.
		Glass is produced in standard metric sizes of 2, 3, 4, 5, 6, 8, 10, 12, 15, 19 and 22 mm.
		Building codes across the world restrict the use of annealed glass in areas where there is a high risk of breakage and injury, for example in bathrooms, in door panels, fire exits and at low heights in schools.
	www.biocrawler.com /encyclopedia/Glass (3953 words)

	!Glass \| Industrial glass\| Float glass\| glass making\| glass manufacturer\| colour glass\| uses of glass\| broken Glass\| ...
		As the glass flows down a long narrow tunnel, the temperature is gradually reduced until the sheet can be lifted from the tin onto rollers, where it is further cooled gradually so that it anneals without strain and doesn't crack from the change in temperature.
		Most glass for windows up to the early 19th century was made from rondels, while most window glass during the 19th century was made using the bottle method (these 'bottles' were 6 to 8 feet (2 to 2.5 m) long and 10 to 14 inches (250 to 350 mm) in diameter).
		Glass of lower quality, sheet glass, was made by drawing upwards from a pool of molten glass a thin sheet, held at the edges by rollers.
	www.floatglass.bz (3112 words)

	Talk:Glass - Wikipedia, the free encyclopedia
		Sometimes the term glass is used to emphasize that a system that has been kinetically trapped in a non-equilibrium state, but in other cases the term glassy response is used to describe any fast response of a viscous liquid at equilibrium.
		It is correct that in a phase diagram the boundary between the liquid phase and the glass phase is not a phase transition.
		The fact that glass "creeps" doesn't really belong in the room temperature flow argument, because (as a previous editor neglected to mention) creep is a response to high temperature as well as stress.
	en.wikipedia.org /wiki/Talk:Glass (6331 words)

	Wikinfo \| Glass
		Glass is a transparent, relatively strong, hard-wearing, essentially inert, and biologically inactive material which can be formed with very smooth and impervious surfaces.
		Pilkington's invention of the float-glass process, in which molten glass is poured onto molten lead as it solidifies, made it possible to produce large sheets of flat glass more cheaply and with better quality than the previous process in which the glass was passed through rollers.
		Glass articles intended to survive rough handling, or rapid temperature changes, are sometimes toughened by rapid and localised cooling of their surfaces during the manufacturing process (called "tempering").
	www.wikinfo.org /wiki.php?title=Glass (1422 words)

	The Pervasive Glass Flow Myth (Site not responding. Last check: 2007-10-22)
		This process involves a roughly nine pound chunk of glass blown into a crown shape which is then heated in a furnace and then spun.
		When the process is completed, the disk will be roughly five feet in diameter and be thinnest towards the outsides and thickest (and most deformed) in the center.
		The glass maker will then cut the disk into the rectangular shape of the windows with the end coming from the center being thicker than the end from the edge.
	www.georgiasouthern.edu /~jdegiro1/crown.html (228 words)

	Articles - Glass (Site not responding. Last check: 2007-10-22)
		Glasses used for making optical devices are commonly categorized using a six-digit glass code, or alternatively a letter-number code from the Schott Glass catalogue.
		Glass making instructions were first documented in Egypt around 1500 BC, when glass was used as a glaze for pottery and other items.
		Colored glass is often used, though sometimes the glass is painted; notable examples of painted glass include the work of contemporary artists Judith Schaechter and Walter Lieberman, and innumerable examples of stained glass, such as those by John La Farge in Boston´s Trinity Church.
	www.zdiamond.net /articles/Glass (2917 words)

	Collecting antique American clocks comes as a natural outgrowth of my interest in the nation
		Glass at this time was created by attaching a molten lump of glass to a blowpipe then blowing a bubble into the lump.
		By about 1825 the crown glass process was replaced by a technique in which the lump of molten glass was blown into a long cylinder.
		Because the glass cylinder from which the flat panes were eventually cut was blown and not pressed there were small variations in thickness from one area to the next.
	www.xrestore.com /pages/Glass.htm (1537 words)

	Glass: Liquid or Solid -- Science vs. an Urban Legend
		(Thus, by definition, all glasses are amorphous, but not all amorphous solids are necessarily glassy.) The glass transition is marked (as a function of temperature) either by a change in slope of extensive thermodynamic quantities (e.g., volume or entropy) or, equivalently, as a discontinuity in derivative quantities (e.g., specific heat or thermal expansivity).
		To emphasize this a professor would state "Glass is a liquid which has lost the ability to flow", and some undergraduate, with his mind more on the Friday night date than on the physics of glass, would remember only "glass is a liquid"...
		It is possible that the "glass is a liquid" urban legend originated with a misreading of a German treatise on glass thermodynamics.
	dwb.unl.edu /Teacher/NSF/C01/C01Links/www.ualberta.ca/~bderksen/florin.html (2007 words)

	Is glass liquid or solid?
		The notion that glass flows over time is just the mistaken thinking of someone who was unaware that medieval glass blowers had not developed a way of making very flat glass of even thickness.
		Glass are counted as solid material when we are looking at its structure and behaviour because most of inorganic materials which we are encounter in our daily lives are crystalline, the notable exception being glass which is super cooled liquid.
		Yes, it is right as you mention glass flow, and different type of glasses have their own time limit, but the point is are we taking into the consideration if really glass is solid or not.
	www.physicsforums.com /showthread.php?t=106653 (2070 words)

	Antique Window Glass - Supercooled (Site not responding. Last check: 2007-10-22)
		Stories are told of glasses flowing under their own weight: of ancient windowpanes that are thicker at the bottom; of glass that has sagged in storage.
		In the "zero-creep" phenomenon the thermometer bulbs are heated above the glass transition temperature and the lattice slowly adjusts to the equilibrium (supercooled) liquid structure stable at that elevated temperature.
		The glass was amazingly flat and uniform in thickness for a hand-fabricated disk 5 ft in diameter, but not in comparison to sheet glass drawing processes of recent years and float glass processes widely used now.
	www.glasslinks.com /newsinfo/supercooled.htm (2011 words)

	Glass - Questionz.net , answers to all your questions (Site not responding. Last check: 2007-10-22)
		Common glass is mostly amorphous silicon dioxide (SiO2), which is the same chemical compound as quartz, or in its polycrystalline form, sand.
		Laminated glass Large sheets of glass can cause a serious hazard when broken, as they tend to form shards with very sharp edges.
		* if glass flows at a rate that allows changes to be seen with the naked eye after centuries, then changes in optical telescope mirrors should be observable (by interferometry) in a matter of days - but this also not observed.
	www.questionz.net /List_of_phobias/Glass.html (1446 words)

	Subject: Glass Flow [Was Re: OBJECTIONS to afu faq (v.2.50 1/194) ] Date: 30 Jan 1994 04:1
		Paul provided the abstract of that paper, which read: In an attempt to dispel the notion that colonial window panes are thicker at the bottom than at the top because the glass is a supercooled liq.
		For window glass, Tg > (measured) is 550 degrees C. For the limiting case of infinite time > the thermodynamically calculated ideal glass transition state Tg(0) > for window glass is 270 degrees C. For Pyrex the values are 550 and > 350 deg., respectively.
		According > to R. Lemker (Operations Manager, Fallbrook Plant, Corning Glass, > Corning, NY) the instructions are to avoid damage to the ends of the > tubing, not to keep it from sagging.
	www.skepticfiles.org /urban/glasswin.htm (744 words)

	Science/Glass Flow/glass flow the thread
		Glass does not so much flow as gradually bend under the influence of gravity, being, as it is, an amorphous solid.
		Glass viscosity is around 10^13 poise, which amounts to forces several orders of magnitude greater than what is needed to break glass, should it flow perceptibly at room temperature -- even over several centuries.
		Glass would have to be subjected to stresses IN EXCESS of that amount, in a sustained fashion for this to begin to occur.
	tafkac.org /science/glass.flow/glass_flow_the_thread.html (5347 words)

	♧ Glass Guide (Site not responding. Last check: 2007-10-22)
		You can get a special pair of safety glasses that have polycarbonate lenses and frames or lycarbonate shield from an eye doctor.
		If you require this type of eyewear inform your employer they should provide you with all the necessities to keep you safe at the job.
		There are two types of safety glasses your employer may have to provide depending on your job, basic or high impact.
	www.glass-guide.us /crown-imperial.html (89 words)

	Science/glass flow
		Subject: Glass Flow [Was Re: OBJECTIONS to afu faq (v.2.50 1/194) ]
		[...] >By the same token, this does not mean that >we can observe the flow of glass by simple >empirical methods such as looking at the >thickness of window panes.
		In an attempt to dispel the notion that colonial window panes are thicker at the bottom than at the top because the glass is a supercooled liq.
	tafkac.org /science/glass_flow.html (823 words)

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