Tin

The discovery of tin and its impact on metalworking marked a major turning point in human history. Around 3500 BCE, metalworkers in what is now Turkey discovered that adding tin to copper created a stronger metal—bronze. This discovery led to the Bronze Age, when people started using bronze to make tougher tools, weapons, and even jewelry. Bronze, made from about 10% tin and 90% copper, was much harder than pure copper. This combination of metals advanced technology and allowed civilizations to thrive.

By 1000 BCE, large deposits of tin were discovered in England, becoming one of the most important sources of tin in the world. The tin was traded across the Mediterranean, fueling the bronze production that powered early European and Middle Eastern civilizations. The importance of tin in trade and industry was so significant that it motivated the Roman invasion of Britain in 43 CE, as the Romans sought control over the lucrative mines.

By the 1300s, tin was being used as a protective coating for other metals, a process known as tinning, to prevent corrosion. This process eventually led to the development of tinplate in the 1600s, which involved dipping sheets of iron into molten tin. Tinplate became widely used for making everything from cookware to preserving food in cans—a technique patented by Peter Durand in 1810.

Today, tin is still widely used across the world with 80 billion tin cans produced every year. It continues to be a valuable and versatile metal with its ability to resist corrosion and its use in float glass production (a process that makes perfectly flat glass) for windows. Today, tin is also being used in energy-efficient glass coatings and thermal insulation. As new green technologies develop, tin is set to play a key role in making our world more sustainable!

Ordinary tin, or white tin, is a silver-white metal. It is soft, malleable, somewhat ductile, and has a highly crystalline structure. A bar of tin can be bent by hand, breaking its crystals and producing an audible “tin cry”—a high-pitched creaking sound.

Probably the best-known application of tin is the tin can. It is actually tin-plated steel; the tin prevents corrosion. However, tin is most useful when mixed into an alloy with other metals. Bronze is an alloy of copper and tin. Solder, used for permanently binding metals together (including electrical contacts), is an alloy of lead and tin. Organ pipes are also lead and tin. Pewter, often used in metal dishes, decorative items, and jewelry, is an alloy of tin, antimony, copper, and bismuth (and sometimes silver).

A crystalline alloy of niobium and tin is superconducting at very low temperatures. (Currents flowing through ordinary conductors lose energy by generating heat. But superconductors conduct electricity with no energy loss.) This allows the construction of relatively small superconducting magnets, just a couple kilograms, that consume virtually no power. Yet they generate magnetic fields as strong as those of a multi-ton, high-power electromagnet.

Tin is also useful in glassmaking. Window glass is made by floating molten glass on top of molten tin to get flat, parallel surfaces. And tin salts sprayed onto a glass surface produce an electrically conductive coating. These can be used for panel lighting or frost-free windshields. And transparent, conducting films, like in liquid-crystal displays, are often made from tin oxide.

Finally, in organic chemistry applications, “organotin” compounds are especially valuable as PVC-plastic stabilizers and biocides. Biocides include pesticides, fungicides, algaecides, wood preservatives, and antifouling agents.

At normal pressure, tin has two allotropes, or internal crystal structures that result in different physical properties and appearances. The element switches from one to the other at 13.2°C (55.8°F).

Gray tin, or alpha tin, exists below 13.2°C. It is a dull gray powder. It is also a nonmetal, held together internally by covalent chemical bonds (shared electrons between atoms). When heated above 13.2°C, it changes into white tin, or beta tin, the metal. While white tin has several uses, gray tin has few, other than some highly specialized semiconductor applications. To prevent white tin from degrading into gray tin at coolish everyday temperatures, small amounts of antimony or bismuth can be mixed into it. Other metal additives also help control the transition from white to gray.

Tin is found chiefly in the mineral cassiterite (tin oxide, or stannic oxide, SnO₂). This and other tin-containing minerals are usually found with granite. Most of the world's supply of tin (from cassiterite) comes from Asia and South America. Tin is extracted from the oxide by heating cassiterite ore with coal in a furnace. The carbon in the coal peels off the oxygen to make CO₂, leaving just tin behind.