Years ago, I worked as a nanny for a German family. One summer, they planned a trip back to Germany and gave me time off as well. On the day they were leaving, my employer asked me to fill a bowl with water, place it in the freezer, and once it froze, set a coin on top of the ice.
I had no idea why. She was a reserved woman, her Chinese wasn’t great, and I rarely spoke with her. I didn’t dare ask questions — I simply followed the instructions. Then the family of three flew home to Germany.
A month later, they returned. As I prepared to resume work, the German lady told me to throw away everything in the freezer: beef, lamb, ribs, chicken, duck, seafood — all kinds of food. I was baffled. These items had been frozen for a month. Why discard them? They looked perfectly fine.
Still unsure, I said nothing. Instead, I packed the food into bags so I could take it home to share with my neighbors. My employer often gave me food that was close to expiring, so it seemed only natural to share it again.
Before leaving work that day, I carried the bags home. My neighbor, Aunt Xu, was thrilled — she knew I couldn’t finish everything myself and that I would share some with her.
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I did. I split everything in half and stored the rest in my own freezer, intending to cook it later when work wasn’t so busy.
The next morning, I ran into Aunt Xu. She looked unwell. Her entire family had diarrhea, she said, and asked whether the meat I gave her had gone bad. I told her the truth: my employer had asked me to throw everything away; I had taken it home because I couldn’t bear to waste it.
She urged me to throw the rest out immediately — “the food is spoiled,” she said.
I couldn’t understand it. Everything had still been frozen solid. How could it be bad?
The freezer coin trick
Later that day, I went to work and continued cleaning the freezer. I noticed the bowl of ice was still there — but the coin was no longer sitting on top. Not thinking much of it, I removed the bowl and set it aside to thaw before washing it.
As the ice melted, I suddenly saw the coin resting at the bottom. The same coin I had placed on top a month earlier — now lying beneath the melted water. I brought it to my employer.
She asked, in halting Chinese, “The coin… was at the bottom?”
“Yes,” I replied.
She turned to her husband and spoke rapidly in English. I didn’t understand, but a moment later he came over to explain: “When the coin sinks to the bottom, it means the power went out while we were away. The ice melted, everything in the freezer thawed and spoiled, and when the electricity returned, everything froze again — including the water in the bowl. That’s why the coin ended up at the bottom.”
Suddenly everything made sense — why Aunt Xu’s family got sick, and why the food was spoiled even though it looked frozen after the outage.
From that experience, I learned a simple, practical trick:
Before a long trip, freeze a bowl of water and place a coin on top. When you return, check the coin:
1. If the coin is still on top
There was no power outage. Your food is safe.
2. If the coin is frozen halfway down
There was a short outage and partial thawing. Some food may still be usable — but be cautious.
3. If the coin is at the bottom
There was a long outage, the freezer fully thawed, and everything refroze.
All food should be discarded.
This one small trick can save you from food poisoning — and from making the same mistake I did.
