Glass

Raw Materials Soda-lime-silicate which is made from –silica (sand) –Soda –Lime

Raw 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

Manufacturing 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 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 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 Glass Flat drawn sheets can be drawn in thickness of 18, 24, 32 thick sheets oz/ft3 –Single strength = 18 –Double strength = 24

Sheet Glass Quality –AA – flat glass – superfine glass for silvering –A – glazing quality glass – pictures framing –B – general glazing

Glass 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 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 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 glass Glass has a low r – value Ways to make glass more insulation –Double pain –Triple pane –Argon gas –Low e coating