Everyone trusts a freezer to keep food safe long-term, but even new units can fail due to power cuts, maintenance issues, or unexpected outages. When this happens, food can partially or fully defrost and refreeze, making it hard to know what is still safe—especially meat and dairy, where bacteria can grow quickly.

A simple method shared online helps solve this problem using a cup of frozen water and a coin. Sheila Pulanco Russell explained: “For those of you that are evacuating from the coast,” and added, “I just heard a great tip. It’s called the one cup tip. You put a cup of water in your freezer. Freeze it solid and then put a quarter on top of it and leave it in your freezer.“

She further explained how it works: “That way when you come back after you’ve been evacuated you can tell if your food went completely bad and just refroze or if it stayed frozen while you were gone. If the quarter has fallen to the bottom of the cup that means all the food defrosted. And you should throw it out. But if the quarter is either on the top or in the middle of the cup then your food may still be ok.”

She also advised long-term use: “It would also be a great idea to leave this in your freezer all the time and if you lose power for any reason you will have this tip to fall back on. If you don’t feel good about your food, just throw it out. The main thing is for all to be safe.”

The idea quickly gained attention online, with reactions like “Brilliant and simple!” and “Have used this for years in the porch freezer.”