玻璃

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玻璃(glass)

硬的物质，其典型为无机化合物的混合物，通常为透明或半透明，坚硬，易碎和不能为自然元素所穿透（玻璃特性）。由高温液态快速转变为固态制成玻璃，如此可避免形成肉眼可看到的结晶体。是电和热的不良导体；混合物中含有某些金属氧化物时，玻璃会呈现出不同的颜色。大多数种类的玻璃容易破碎。黑曜岩是一种自然生成的玻璃。普通玻璃（钠钙玻璃、钠钙矽玻璃）是以矽（二氧化矽）、苏打（碳酸钠）和石灰岩（碳酸钙）为原料，加入镁（氧化镁）可制成平板玻璃；或加入铝（氧化铝）可制造瓶玻璃。熔矽玻璃是极佳的玻璃，但由於纯矽的熔点很高，所以制造费用昂贵。硼矽酸盐玻璃（派热克斯耐热硬质玻璃）因为热膨胀极小，所以被用於制造厨具和实验室用具。铅水晶玻璃则被用於制作高级餐具，不但有沈重的触感，还因折射率高而光彩夺目。更多种类的特种玻璃还包括有光学玻璃、光敏玻璃、金属玻璃和光学纤维。由於玻璃没有明确的熔点，因此大多数种类的玻璃可以在烧热时使用多种技术来塑形，以吹制和模具浇铸两种方法为主。亦请参阅volcanic glass。

English version：

glass

Solid material, typically a mix of inorganic compounds, usually transparent or translucent, hard, brittle, and impervious to the natural elements (“vitreous properties”). It is made by cooling molten ingredients fast enough so no visible crystals form. A poor conductor of heat and electricity, glass takes on colors when certain metal oxides are included in the mix. Most glass breaks easily. Obsidian is a naturally occurring glass. Everyday glass (“soda-lime” or “soda-lime-silica”) is made of silica (silicon dioxide), soda (sodium carbonate), and limestone (calcium carbonate), with magnesia (magnesium oxide) for sheet glass or alumina (aluminum oxide) for bottle glass. Fused silica is an excellent glass but expensive because of pure silica's very high melting point. Borosilicate glass (Pyrex) is used for cookware and laboratory glassware because it expands very little when heated. Lead crystal is used for fine tableware. It has a heavy feel and a sparkle due to its high refraction index. Even more specialized glasses include optical, photosensitive, metallic, and fiber-optic. Since glass has no sharp melting point, most types can be shaped while hot by many techniques, mostly blowing or molding. See also volcanic glass.

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