If you’re planning a vacation and leaving food in the freezer, here’s a simple trick you shouldn’t miss. It helps you know whether your frozen food stayed safely frozen while you were away. Power outages can happen without us knowing, causing food to thaw and spoil.

A woman named Sheila Pulanco Russell shared an ingenious method using just a cup of water and a coin. By freezing the water with a coin on top, you can later check if your freezer maintained its temperature. It’s a quick, easy way to make sure your food didn’t secretly thaw and refreeze.

The idea is simple: freeze a cup of water, place a quarter on top, and leave it in the freezer. If you return and the coin is at the bottom, the freezer fully defrosted at some point—meaning the food is likely unsafe. If the coin remains on top or in the middle, your food probably stayed frozen and may still be good.

Still, when in doubt, throw the food out. Your health comes first, and this small trick can help you avoid risks while keeping peace of mind.