The Quest To Make Unbreakable Glass

Glass and our place in the universe (0s)

• Glass is inherently brittle and symbolizes fragility, yet it is expected to be transparent, scratch-resistant, thin, flexible, and unbreakable in modern times (0s).
• Despite its fragility, glass has been a crucial material in human history, transforming the way people live, driving scientific revolutions, and changing perspectives on the universe (23s).
• The development of unbreakable glass was a significant challenge, as seen in the case of Apple's first iPhone, which initially had a plastic screen that scratched easily (42s).
• Steve Jobs, dissatisfied with the plastic screen, approached Wendell Weeks, the CEO of Corning, to create a suitable glass for the iPhone, which led to the development of Gorilla Glass (1m11s).
• The creation of Gorilla Glass was a rapid process, taking only six months to complete, and it was successfully integrated into the first iPhone (1m17s).

How Gorilla Glass works (1m23s)

• Gorilla Glass has been used in various devices such as phones, computers, and wearable devices for the last 17 years and is now used on billions of devices, becoming more durable over time (1m23s).
• A key scratch demo was conducted to compare the scratch resistance of polycarbonate and Gorilla Glass, showing that Gorilla Glass is more resistant to scratches (1m49s).
• To break glass, two things are required: a flaw and stress, as demonstrated by sandblasting a spot on the glass to introduce a flaw and applying stress to break it (2m21s).
• A comparison of the strength of strengthened soda lime glass and Gorilla Glass was made, with Gorilla Glass being significantly more resistant to breaking (2m42s).
• The process of making sharp edges from obsidian, a volcanic glass, has been used by humans for over 1.2 million years for cutting implements, arrowheads, and spear tips (4m11s).
• Obsidian is still used today in some surgical scalpels due to its ability to be sharpened to a very fine edge, with some tips being sharpened to just three nanometers across (4m22s).
• Despite being used for over a million years, glass remains a brittle material that can be prone to breaking, but advancements in technology have led to the development of more durable materials like Gorilla Glass (4m34s).

What is glass? (4m35s)

• Humans began making glass relatively recently, around 5,600 years ago (4m38s).
• The most common type of glass is primarily composed of oxygen and silicon, which are the two most abundant elements in Earth's crust (4m43s).
• Oxygen and silicon can be found naturally in the form of quartz, a crystalline silicon dioxide (4m50s).
• Quartz has a crystalline structure, meaning its atoms are arranged in a regular repeating pattern (4m55s).
• Quartz is the primary component of sand (5m0s).
• Glass can be formed by heating sand to approximately 1700 degrees Celsius until it melts, and then rapidly cooling it (5m5s).
• The rapid cooling process during glass formation prevents the atoms from arranging themselves in a crystalline structure, resulting in glass (5m14s).

Is glass a liquid? (5m15s)

• Glass is considered an amorphous solid because its atoms don't have enough time to return to their periodically arranged crystal structure, resulting in a disorganized arrangement (5m16s).
• The misconception that glass is a liquid likely arises from its amorphous structure, but glass is solid at room temperature because its atoms are fixed in place and cannot flow past each other like in a liquid (5m35s).
• The amorphous structure of glass makes it brittle, as there is no way for the structure to relieve stress, leading to the formation of cracks and eventual fracturing when stress is applied (5m56s).
• A demonstration using sandpaper to represent a rough surface, such as asphalt, shows how a small flaw on the surface of glass can lead to cracking and fracturing when stress is applied (6m17s).
• The demonstration involves using a fixture to bend and pre-stress the glass, introducing a flaw, and then dropping it to test its durability (6m30s).
• The demonstration compares the durability of alternative glass and Gorilla Glass, with the latter withstanding a more severe test, known as the "mega slap," without breaking (6m59s).

Different types of glass (7m29s)

• The basic recipe for glass involves silicon dioxide, but adding other ingredients like sodium carbonate and calcium oxide can change its properties, and this process has been done for thousands of years (7m30s).
• Adding sodium carbonate and calcium oxide to silicon dioxide lowers the temperature at which it becomes liquid from 1700 degrees Celsius to around 1000 degrees Celsius, making it the reason why soda lime glass accounts for around 90% of all glass manufactured today (7m38s).
• Adding boron trioxide to the mixture forms a borosilicate glass, which has a low coefficient of thermal expansion, making it resistant to drastic temperature changes and suitable for laboratory glass like beakers (7m56s).
• Borosilicate glass does not grow or shrink much with temperature changes, unlike regular glass which can shatter when exposed to boiling water due to rapid expansion (8m2s).
• The recipe for Gorilla Glass is secret, but it is based on a combination of silicon, aluminum, magnesium, and sodium, and scientists constantly try different formulations to find more durable and scratch-resistant glasses (8m36s).
• The earliest human-made glass was likely an accident, formed when sand made its way into metalworking furnaces, creating small glass beads (9m16s).
• Glass making became its own art form, used to make decorations, ornaments, statues, tableware, and containers, and its impermeability to water made it ideal for bowls and bottles (9m30s).
• By adding elements like cobalt oxide and cuprite to the glass mixture, glass makers can change the color of the glass, with cobalt oxide producing a vivid blue and cuprite producing red (9m52s).

Invention of transparent glass (9m59s)

• Historical glasses were initially opaque, and it took thousands of years after the invention of glass making to develop transparent glass, which is what we commonly think of as glass today (9m59s).
• The first step towards creating transparent glass was made around 100 AD when glass makers in Alexandria added manganese dioxide to the mixture, resulting in semi-opaque glass that allowed some light to pass through (10m17s).
• Semi-opaque glass led to the use of glass for windows, providing a physical barrier that kept warm air in and wind and critters out while allowing light to shine into homes (10m31s).
• The first truly transparent glass was made many centuries later, around the Italian city of Venice, where the art of glass making was thriving and generating significant revenue (10m48s).
• However, the need for very hot furnaces to make and manipulate glass posed a problem in Venice, a city built almost entirely of wood, leading to frequent accidental fires (11m3s).
• In 1291, the government of Venice relocated all glass makers to the island of Murano to mitigate the risk of fires, and the island became known as the Isle of Glass, famous for producing beautiful and intricate glassware (11m18s).
• Angelo Barovier, a glass maker on the island of Murano, invented clear glass by burning seaweed rich in potassium oxide and manganese to create ash, which he then added to his glass mixture, resulting in transparent glass (11m35s).

Why is some glass transparent? (11m56s)

• Most materials are opaque because when photons hit them, the photons are absorbed, exciting an electron and pushing it up to a higher energy level, but this only happens when the photon's energy matches the energy of an allowed electron transition (11m56s).
• In transparent glass, the energy required to move an electron from a lower state to a higher state is higher than the amount of energy that a photon of visible light has, so the photon just passes right through (12m13s).
• Glass interacts with other parts of the electromagnetic spectrum, absorbing much of the ultraviolet spectrum because UV photons have more energy, making it opaque to UV (12m28s).
• Colored glass is made by adding impurities into the glass, which affects the electron energy levels and changes the color of the glass (12m48s).
• The most common glass used for windows, soda lime, has impurities of iron oxides, which give the glass a green tinge because it absorbs more of the other colors than it does green (13m2s).
• The importance of transparent glass can be appreciated by imagining a scenario where it suddenly disappears, affecting daily life, including windows, glasses, and screens (13m19s).

Invention of glass lenses (14m54s)

• Truly transparent glass was a significant innovation for three reasons, and its development led to the creation of small, thicker-in-the-center glass discs that were ground, shaped, and polished into lenses in northern Italy in the early 1300s (14m58s).
• These early lenses were initially not widely used, except by monks, due to low literacy rates, but they were used to correct farsightedness (15m13s).
• The invention of the printing press around 1440 led to a decrease in book production costs, resulting in increased literacy rates, and subsequently, a growing awareness of farsightedness among the population (15m28s).
• As a result, glasses became a vital tool, and the existing lens technology was available to address the problem of farsightedness (15m48s).
• A father and son duo played a significant role in the development of lenses 150 years after the initial innovation (15m51s).

Development of magnification (15m52s)

• Hans and Zacharias Janssen created the world's first microscope by placing two lenses in line with each other, allowing objects to appear about 20 times their original size (16m0s).
• Antony Van Leeuwenhoek made significant improvements to the microscope in the 1660s by grinding the lenses himself, enabling him to magnify objects 200 times and see human cells (16m16s).
• Robert Hook published "Micrographia," a book featuring sketches of the microscopic world, which was made possible by the use of transparent glass (16m24s).
• Hans Lippershey, an eyeglass maker, applied for a patent for a spy glass in 1608, which was intended for use in warfare to spy on enemies (16m37s).
• Galileo Galilei adapted the spy glass idea to create a telescope, pointing it towards the sky to study the stars and planets, and was able to magnify objects in the night sky by about 30 times (16m55s).
• Galileo's telescope allowed him to observe the craters of the moon, the phases of Venus, and four of Jupiter's largest moons in 1610, providing evidence against the geocentric model of the universe (17m7s).
• The invention of transparent glass was crucial for these discoveries, and four centuries later, it is now possible to create glass that is orders of magnitude more transparent than water (17m30s).
• Modern glass, such as that used in optical fibers, is so transparent that a column as deep as the Mariana trench would allow visibility all the way to the bottom (17m47s).

How to make glass more durable (18m2s)

• To make glass more durable, a process involving an aluminosilicate base and submerging the glass in a potassium salt solution at 420 degrees Celsius is used (18m14s).
• This process replaces some of the sodium atoms in the glass with potassium atoms, which are physically larger, increasing the compressive strength in the surface of the glass and making it more durable (18m41s).
• The increased compressive strength is due to the larger potassium atoms being squeezed together in the same amount of space as before, making the glass more resistant to scratches and drops (18m57s).
• A visual difference in size between the treated and untreated glass cannot be seen, but the durability difference can be observed through testing, such as dropping heavy objects onto the glass (19m5s).
• Scientists at Corning are constantly refining the process to make the glass even more durable, conducting various tests such as bending, scratching, and dropping heavy steel balls onto the glass (20m28s).
• The team at Corning also tests different glass prototypes, including replica phones with various glasses for the screen, dropping them from increasing heights to test durability (20m57s).
• The goal of these tests is to make the next version of Gorilla Glass even more durable than it already is, with the understanding that while the glass is still not perfect and can crack, it is constantly improving (21m10s).