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