Notes:
see-through 透明な;
the Bronze Age 青銅器時代;
silica シリカ;
lime 石灰;
alkali アルカリ;
crystals 結晶
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Glass is an incredible material made from simple ingredients. It can be colored or clear, plain or decorated with many colors. Glass can be see-through, slightly see-through, or not see-through at all. It’s light and doesn’t let liquids through. It can be cleaned easily and used again. Glass is strong but can break easily, and it often looks very beautiful. It’s used in many ways – for drinking glasses, containers, in buildings, and for designing things. Glass has been used since the Bronze Age, about 3000 B.C. It was first made from silica, lime, and an alkali like soda or potash. Even today, these are still the main things used to make glass. When heated, these things get soft and can be shaped into many different shapes and sizes. Glass is different from metals because it doesn’t have crystals in it. Instead, it keeps a random liquid-like structure. This is why glass can break easily and why it changes over time, especially if it gets wet.
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