The “quarter on a frozen cup of water” trick
This is a simple way to check whether your freezer lost power while you were away.
How it works
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Fill a cup with water and freeze it solid.
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Put a quarter (25-cent coin) on top of the ice.
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Leave the cup in the freezer while you’re away.
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When you return, check where the coin is.
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Quarter still on top: The ice probably remained frozen.
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Quarter near the bottom: The ice likely melted substantially and then refroze, suggesting the freezer became warm enough for a significant period.
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Quarter somewhere in the middle: There may have been partial thawing.
Why people do it
During a prolonged power outage, frozen food can thaw. If the freezer gets warm enough, food safety can become an issue, even if everything looks frozen again after power returns.
However, the quarter test cannot tell you exactly how long the freezer was above a safe temperature, so don’t use it as the sole basis for deciding whether questionable food is safe.
For a more reliable approach, keep a freezer thermometer inside the freezer. A properly operating freezer should generally be at 0°F (−18°C) or below.
