Low-Tech: Stone and Earth

Low-Tech: Stone and Earth

The most durable items from antiquity, and therefore those about which we know the most, were made from inorganic materials, starting with stone and earth.

Precious Stones

Tiny quantities of semiprecious stones were used for ornamentation far into antiquity, but they weren't seriously mined or worked until the sixth millennium B.C. in Egypt and China. Bronze Age civilizations used turquoise, jade, lapis lazuli, jet, and varieties of quartz. These stones were soft enough to carve into seals and tiny figurines, or into very thin pieces for inlay.

Precious stones were discovered later. Emeralds were mined in Egypt by the early second millennium B.C.; sapphires and rubies, in southern Asia in the first millennium B.C.; and diamonds, in south-central India around the fourth century B.C.

Most of these stones came from a handful of sources. For example, Egypt remained the Old World’s sole source of emeralds well into the Middle Ages, while all ancient lapis lazuli came from northeastern Afghanistan.

Note that such stones were used almost entirely for decoration at TL0-4. Watch movements using jeweled bearings were invented early in the 18th century (very late TL4).

Flaked Stone Tools

Produced at least 2.5 million years ago, the oldest surviving tools are made from flaked or chipped stone. Materials such as flint, chalcedony, chert, and obsidian have a glassy internal structure. When a mass is struck, the shock of the impact propagates in a predictable wave and cracks the stone along the wave's edge.

The simplest stone tools were made by striking a stone with a hammer – typically a convenient pebble – to knock off a single flake with a sharp edge. Flake tools can be extremely sharp, but their edges wear down after a few cuts, even on something soft such as cloth fibers. More durable tools were shaped by striking multiple flakes from a core. The working edge was actually a series of small edges produced by removing the waste flakes, giving a serrated look. Core tools aren't as sharp as flakes, but can be "resharpened" by knocking off more flakes.

By the Neolithic, pressure-flaking was developed: a punch made of horn or bone was pressed against a core's edge to produce minuscule flakes. Some TL1 societies, notably the more sophisticated civilizations of Mesoamerica, could produce pressure-flaked blades five or six inches long and less than a quarter-inch thick, each with a razor-sharp edge. Though larger flakes and well-shaped cores could be used by themselves, many stone tools were incorporated into composite items; e.g., arrow and spear heads were attached to wooden shafts. As stone tools become more sophisticated, very small stone parts – microliths – came into use. Tiny flakes were set in wood or bone handles to yield sickles, or added to spears and arrows as barbs.

Ground Stone Tools

Ground stone axes were made from extremely hard minerals such as basalt and jadeite. Stones were given a rectangular or oval shape by pecking and rubbing against other stones, and then one end was polished down to an edge. This wasn't particularly sharp – perhaps comparable to a dull slot-head screwdriver. It was more durable than a chipped stone tool, though! Fixed to a wooden haft, it could fell trees or break bones. When the edge dulled from wear, more grinding could resharpen it. Softer stones such as limestone and pumice could be shaped more quickly, yielding tools for grinding grain and other dried foods.

Given their great weight, ground stone tools are usually associated with sedentary cultures. Nomadic hunter-gatherers might carry a ground stone axe or mace, but a heavy bowl or grinding stone is too inconvenient to lug around.

Cut Stone

By TL1, sedentary societies began to make use of a different range of stones. Blocks of stone were cut by a number of methods, most often direct chiseling, sawing, abrading with sand or thick wire, and drilling. Although stone was still relatively expensive, entire stone buildings became affordable, and stone quickly became the material of choice for palaces, fortifications, and sacred buildings.

Gypsum was one of the first stones deliberately shaped for building; from the Bronze Age through the Middle Ages, civilizations around the Mediterranean used it as a structural or decorative material. Sandstone also saw use, notably in the American Southwest. Slate – which breaks easily into flat plates – was employed occasionally for construction and frequently for roofing. Limestone, though, became the overwhelmingly popular material, used for everything from the Pyramids to Gothic cathedrals. It was common and, while harder than gypsum and sandstone, balanced durability and workability. Even harder stones, notably marble and to a lesser extent granite and basalt, were on occasion used for particularly fine masonry, but the cost was usually prohibitive.

Stone was cut for tools and portable decorations, too. The usual building stones were shaped into both fine sculptures and sophisticated grindstones that more efficiently turned grain into flour. The Vikings made extensive use of soapstone, which was soft enough to carve with iron knives.

Earthenware and Brick

Pottery first appeared around 12,000 B.C., in Japan. It's made of a material common everywhere: dirt. Wet clay – possibly containing an admixture of sizing (sand, shell, or ground waste pottery), which stiffens the clay and prevents slumping during firing – may be shaped, left to dry, and baked to at least 1,080°F. The clay particles fuse into chemically stable earthenware pottery.

Indefinitely reusable and resistant to moisture and vermin, pottery is excellent for long-term storage. However, pottery vessels are also brittle and heavy. Containers light enough to be easily portable are fragile, while those thick enough to withstand jostling are too heavy to carry casually. Thus, they are the storage of choice only for sedentary peoples. While invented by hunter-gatherers, pottery didn't really take off until the rise of agriculture.

Formed into blocks rather than vessels, pottery becomes brick. Clay for bricks was sometimes mixed with straw or pierced with holes to lighten the final product. Brick is far more durable than any material short of stone, but also less expensive than stone.

High-Fired Ceramics

Fired to 1,700°F, ceramics start to vitrify, or become glassy, throughout. The resulting materials, sometimes called "stoneware," are tougher and more waterproof than earthenware, but still slightly porous. However, stoneware needs more than just heat. Many clays don't vitrify at such temperatures – they melt! Stoneware requires more careful clay processing and a more limited range of sizing materials than earthenware.

The first stoneware appeared around 3000 B.C., in Mesopotamia. Fully vitrified stoneware – which is completely waterproof – dates to the first millennium A.D., in China. It appeared even later in Europe.

Porcelain, first produced in China late in the first millennium A.D., is a particularly prized high-fired ceramic; see The Race for Porcelain (below). It's made from petuntse and kaolinite – not particularly common minerals – and the resulting clay is difficult to work. When fired at 2,200°F, however, it completely vitrifies, becoming both waterproof and slightly translucent.

The Race for Porcelain

The story of porcelain in Europe is a low-tech tale of scientific research and industrial espionage. Chinese porcelain commanded astronomical prices in Renaissance Europe. However, its production was a mystery to European potters. Powerful patrons, seeking money and prestige, sponsored workshops attempting to re-create Chinese ceramics. Experimentation produced useful near-misses such as "soft" porcelain (which mixes glass with white clay) and bone china (which contains large quantities of bone ash), but the secret remained elusive for centuries.

In 1709, Johann Böttger, an alchemist working for the Elector of Saxony, finally produced a hard, translucent ceramic that could be decorated with glazes resembling those used in China. The formula for porcelain was a jealously but imperfectly guarded secret for years thereafter. Nevertheless, the industrial spies who uncovered Böttger's secret kept it hidden themselves, and Europe had only three factories producing porcelain until the middle of the 18th century.

Glass

Historical glass was made of silica, which forms the body of the glass; a flux (usually sodium carbonate), which lowers silica’s melting point from above 4,000°F to just over 2,000°F; and lime, which controls the water solubility of sodium carbonate and keeps the glass waterproof. Metallic salts were sometimes added for color. Production methods placed significant limits on glass' form and quality.

Core Formation (TL1):

In this process, developed around 3500 B.C., raw materials were combined and sometimes layered to produce multiple colors, surrounded by fuel, and completely covered to retain heat. This produced a biscuit-shaped lump of colorful but mostly opaque glass. Some shaping was eventually possible, with cores being shaped around earthen forms that were scraped out later.

Glassblowing (TL2)

In the first century A.D., improved furnace designs allowed glassmakers to use open furnaces and inflate lumps of molten glass on the ends of metal tubes, producing attractive thin-walled vessels.

Optical Glass (TL3)

By the 11th century in the Near East and 12th century in Venice, glassblowers developed truly clear and colorless glass suitable for corrective lenses and transparent windows. They used a potassium-rich flux and naturally pure sand without color-causing metallic salts. Glass mirrors backed with silver foil began to compete with heavier, more expensive mirrors made from solid metal plate. However, metal mirrors remained in use for some purposes. At TL4, Isaac Newton invented an alloy for telescope mirrors (see GURPS Low-Tech Companion 1), called speculum metal: a tin-heavy bronze with arsenic added to remove the red-orange color.

Mortars and Mineral Adhesives

A mortar is a mixture of an adhesive and sand, extending the adhesive and giving it greater strength once set.

Mud (TL0)

A mixture of dirt and water is extremely vulnerable to water, but it's very cheap and makes a good windproof surface. Consequently, it was the material of choice for many domestic structures in dry environments. Reduce the HP of stone or brick buildings using mud mortar by 5%.

Plaster (TL1)

Plaster, made from burnt gypsum, was used as early as 7000 B.C. The most common application was smooth wall surfaces, but it could be poured into molds to produce inexpensive sculpted decoration. Plaster is a good background for painting, but the artist must work quickly, while it's still wet! Reduce the HP of stone or brick buildings using plaster-based mortar by 2%.

Lime (TL1)

Serious structural adhesives are based on lime, which was in use by 4000 B.C. Lime is produced by heating limestone to 1,500°F, which turns it into a powder. Quicklime, the initial product of such heating, is a caustic powder (Lime Powder). It's also unstable – over time, it reabsorbs atmospheric carbon dioxide and reverts to limestone.

For safe storage and handling, it's mixed with a little water to produce "slaked lime." Adding more water gives a paste that sets into a solid form. Mixed with salt and a lot of water, quicklime becomes whitewash: a rough, thick white paint used from at least late TL2. Lime has also been used as a bleaching agent and a cleanser.

Concrete (TL2)

Concrete is a mixture of lime mortar, pozzolana (a volcanic ash), sand, and stones. It's waterproof and even sets underwater. This mixture was first used by the Greeks as early as 500 B.C. Roman masons realized that it could be poured into wooden forms and set strongly enough to serve as a structural material in its own right.

Inferior concretes – not as strong, but still water-resistant – could be made with ground pottery in place of pozzolana. Both fell into disuse by the Middle Ages, perhaps because they required specialized knowledge to compose and use.