Martin McBride Carterton U3A

ORIGINS OF GLASS DECORATIVE GLASS MAKING EARLY FLAT GLASS MANUFACTURE MODERN GLASS PRODUCTION

WHO AM I … WHAT DO I KNOW ABOUT GLASS Applied Chemistry Specialised in Glass Technology and Fuel Technology One of the “Old School” Joined Pilkington Glass in 1963 and retired from Pilkington Glass in Worked in Mexico, Australia, Sweden, South Africa, Visited Germany, France, Denmark, Poland, USA, After retiring worked in Egypt

WHAT IS GLASS Glass is not a solid. Glass is a supercooled liquid. A brittle transparent solid with irregular atomic structure. A container for holding liquids while drinking.

COMPOSITION OF GLASS Normal window glass.... Soda Lime 70% SiO Sand 20% Na2CO3.....Soda Ash 10% Ca2Co Lime Lead Glass contains 20% PbO....Lead oxide Borosilicate contains at least5% Boric Oxide

ORIGINS OF GLASS What is a Fulgerite A naturally occurring form of glass Created when lightening strikes the desert

ORIGINS OF GLASS

FULGERITE SAMPLES

OBSIDIAN Obsidian is formed by volcanic activity Felsic lava extruded from a volcano cools rapidly with minimum crystal growth Felsic substances are high in silica Another form of natural glass

OBSIDIAN Because of this lack of crystal structure, obsidian blade edges can reach almost molecular thinness, leading to its ancient use as projectile points and blades, and its modern use as surgical scalpel blades

OBSIDIAN

Mammoth Lakes in California has an obsidian dome At considerable personal expense I have obtained some samples of obsidian So each of these samples cost me £1000 !!!

OBSIDIAN

Now here are some holiday photos

OBSIDIAN Now this sample was too big !!!

ORIGINS OF GLASS MANUFACTURE No one knows exactly when or where glass was first made. Glass appears to have been produced as far back as the second millennium BC by the Egyptians or the Phoenicians. The Egyptians used a method called core-forming. A shaped core was made of clay and dung, then molten glass was wrapped around it and shaped by rolling it on a smooth surface.

ORIGINS OF GLASS MANUFACTURE Early Roman Glass Samples

ORIGINS OF GLASS MANUFACTURE Early Roman Glass Samples Mid 4 th Century

NEXT STAGE Around the end of the 1st century BC, a new method, glass blowing revolutionised glass production.

DECORATIVE GLASS MURANO MURANO glassmakers banished to the island in 1291 By the 14th century, glassmakers were allowed to wear swords and enjoyed immunity from prosecution. By the end of the 16th century, three thousand of Murano island's seven thousand inhabitants were involved in some way in the glassmaking industry.

DECORATIVE GLASS

ORIGINS OF FLAT GLASS MANUFACTURE Bulls Eye or Crown method Blow…….split…….. spin

CYLINDER BLOWN MANUFACTURE Blown as large cylinder 1825 Swung over a pit Laid on a table and split

CYLINDER PRODUCTION

CAST METHOD The molten glass was poured onto a special table and rolled out flat. After cooling, the plate glass was ground on large round tables by means of rotating cast iron discs The result of this "plate pouring" process was flat glass with good optical transmission qualities. When coated on one side with a reflective, low melting metal, high-quality mirrors could be produced.

CAST METHOD

FLAT DRAWN PROCESS The Pittsburgh Process, invented by PPG in the 1920’s, involves drawing a continuous sheet of molten glass from a tank vertically up a four-story forming-and-cooling tower

ROLLED PLATE Continuous production furnace Passed through water cooled rollers Cut into plates Sent to another factory Ground and polished Continuous grinding & polishing.

ROLLED PLATE

MODERN GLASS MAKING Window Glass

TYPICAL GLASS COMPOSITION BODY TINTED GLASS GREEN GLASS IRON OXIDE GREY GLASSCOBALT OXIDE BRONZE GLASSSELENIUM OXIDE BLUE GLASSCOBALT OXIDE MORE

MODERN GLASS MAKING Raw materials mixed to give homogeneous mix Fed into a regenerative furnace with “cullet” Heated to 1550 centigrade Stirred to ensure perfect mix Cooled to about 11oo and poured onto molten tin Gradually cooled to about 900 and into annealing lehr Cooled to room temperature and cut and snapped

MODERN GLASS LINE

GLASSMAKING Inside a Furnace

GLASSMAKING Warehouse View

GLASSMAKING Cold End of the Line

GLASSMAKING Cold End of the Line

USES OF GLASS Window Glass Automotive Screens Specialist Coated Products Aircraft Glass

LIBYA IN THE NEWS Lockerbie bombing Dec 21 st 1988 Laminated windscreen

Specialised glasses Pan Am drops from 30,000 feet over Lockerbie Windscreen intact Cannot use as an advert

Technical Info While fused quartz (primarily composed of SiO2) is used for some special applications, it is not very common due to its high glass transition temperature of over 2300 °C. Normally, other substances are added to simplify processing. One is sodium carbonate (Na2CO3), which lowers the glass transition to about 1500 °C. However, the soda makes the glass water soluble, which is usually undesirable, so lime (calcium oxide (CaO), generally obtained from limestone), some magnesium oxide (MgO) and aluminium oxide (Al2O3) are added to provide for a better chemical durability. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass.[3] Soda-lime glasses account for about 90% of manufactured glass.

SHORT VIDEO OF FLOAT GLASS Pilkington short film Shown as part of guided tours Filmed in various locations

Any questions?