Low-Tech excerpt

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<span><h1><em>GURPS Low-Tech</em></h1>
	<span><h2>Core Technologies</h2>
		<p>The basic technological building blocks of the ancient world were an extremely small subset of those of the Industrial Age...</p>
		<span><h3>Materials</h3>
			<p>For most of its existence, humanity has used materials taken from the environment and only lightly processed...</p>
			<span><h4>Stone and Earth</h4>
				<p>The most durable items from antiquity, and therefore those about which we know the most...</p>
				<span><h5>High-Fired Ceramics</h5>
					<p>Fired to 1,700 °F, ceramics start to <em>vitrify</em>, 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.</p>
					<p>The first stoneware appeared around 3000 BCE, in Mesopotamia. Fully vitrified stoneware – which is completely waterproof--dates to the first millennium CE, in China. It appeared even later in Europe.</p>
					<p>Porcelain, first produced in China late in the first millennium CE, is a particularly prized high-fired ceramic; see <em>The Race for Porcelain</em> (below). It's made from <em>petuntse</em> and <em>kaolinite</em>--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.</p>
					<span style="float:right;width:50%;border:1px solid black;padding:0.5em;margin:0.5em;"><h5>The Race for Porcelain</h5>
						<p>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 recreate 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.</p>
						<p>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</p>
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				<span><h5>Glass</h5>
					<p>Historical glass was made of <em>silica</em>, which forms the body of the glass; a <em>flux</em> (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's form and quality</p>
					<span><h6>Core Formation (TL1)</h6>
					<p>In this process, developed around 3500 BCE, 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.</p>
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					<span><h6>Glassblowing (TL2)</h6>
					<p>In the first century CE, 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.</p>
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					<span><h6>Optical Glass (TL3)</h6>
					<p>By the 11th century in the Near East and the 12th century in Venice, glassblowers had 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 <strong><em>GURPS Low-Tech Companion 1</em></strong>), called <em>speculum metal</em>: a tin-heavy bronze with arsenic added to remove the red-orange color.</p>
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