Glass. Raw Materials Soda-lime-silicate which is made from –silica (sand) –Soda –Lime.
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Transcript of Glass. Raw Materials Soda-lime-silicate which is made from –silica (sand) –Soda –Lime.
GlassGlass
Raw MaterialsRaw Materials• Soda-lime-silicate which is made
from– silica (sand)– Soda– Lime
Raw MaterialsRaw Materials• Soda and sand melt together produces
sodium silicate – water glass – soluble in water
• Lime is added making a durably glass which withstand elements and water
• Glass has no definite melting point– When heated it first softens so it can be bent– Further heating brings it to the point when it
becomes a thick syrup liquid – can be further worked
– Higher temps it becomes a thin water liquid
ManufacturingManufacturing• Did not begin until 1867 in U.S. –
plate glass• Until 1950’s glass was very
expensive– A large picture window indicated wealth
• 1950’s float glass was invented
Sheet GlassSheet Glass• Manufacturing
– Raw materials ground– Mix into proper
proportions– Mixture called a frit– Frit charged into a glass
furnace with broken glass
– During initial melting stage – chemical reaction occurs between the three ingredients – looks like sticky mass full of bubbles
Sheet GlassSheet Glass• Manufacturing
– Next heat is add so the bubbles move to the top surface
– Mixture is cooled to proper temp. to be drawn
– Mixture moves from furnace to drawing kiln
– Drawing process consist of using a bait – an iron roller – which is lower into the glass – glass sticks to it
– The bait is removed from the kiln carrying a continuous sheet of glass – it passes through a set of rollers to remove imperfections
– Sheets are then cooled in a annealing lehr
– Then trim and stored
Sheet GlassSheet Glass• Flat drawn sheets can
be drawn in thickness of 18, 24, 32 thick sheets oz/ft3– Single strength = 18– Double strength = 24
Sheet GlassSheet Glass• Quality
– AA – flat glass – superfine glass for silvering
– A – glazing quality glass – pictures framing
– B – general glazing
Glass PropertiesGlass Properties• Primary purpose – to allow natural light indoors• Strength Categories
– Annealed glass – cooled slowly to prevent stresses from building in the glass – max compression strength 2500 psi
– High strength glass – heat treated – 2500 psi to 10,000 psi
– Tempered glass – 10,000 psi +• Produce by cutting annealed glass – reheating to 1200
f – cooling the surface very rapidly with cool air while inner core cools slowly produces permanent compression on outside and tension on inner core.
• Optical Properties– Amount of light varies
• Thickness• Surface finish• Type of glass
– 1/8 clear glass 91 %– 1” – clear glass 78%
Specialty GlassSpecialty Glass• Heat strengthened glass
– Cheaper then tempered– Similar process but induced compression stresses is
about 1/3 of tempered• Laminated glass
– Sandwiching vinyl interlayer between sheets of glass bonding the three layers together under pressure and heat.
– Vinyl holds glass together when it breaks– Used in roofs, security purpose, skylights, reduces
risk to people– Better barrier of sound
Specialty GlassSpecialty Glass
• Wired glass– Rolled mesh is place into hot glass– Wire holds broken glass together
• Tinted glass– Adding small amounts of chemical elements to
the molten glass mixture to produce the desire hue
• Visible light transmitted 14 to 75%• Compared to 85% clear glass• Solar heat build up is more of a problem because
more heat is absorbed into building
• Reflective Coated Glass– To achieve low light and low heat intake– Durable films are applied to glass
Insulation of glassInsulation of glass• Glass has a low r – value• Ways to make glass more insulation
– Double pain– Triple pane– Argon gas– Low e coating