十万个为什么·科学启蒙30篇（3）
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Silver Spoons Turn Dark Over Time
为什么银器会变黑
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My grandma’s silver spoons look dull and gray after sitting in the drawer for weeks.
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This dark film forms when silver meets tiny bits of sulfur in the air or food.
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Eggs, onions, and rubber bands make silver darken faster than other items.
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I help polish them gently with a soft cloth and special silver cleaner.
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We store them in cloth bags to keep air and moisture away from the surface.
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The black layer isn’t rust—it’s called tarnish and doesn’t harm the metal.
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Sometimes I notice it first on the fork tines where food touches most often.
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My dad says polishing feels like giving old things a fresh, shiny welcome back.
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Even new silver will darken if left out near a kitchen stove or window.
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After cleaning, the spoons sparkle again when we set the table for dinner.