Status: 06.12.2023, 04:45 a.m.
By: Lennart Schwenck
The cold season is here and with it the winter temperatures: time to dig out the hot water bottles. It lasts longer with a trick.
Kassel – Whether you want to relax with a stomachache or snuggle up under a blanket at home in winter – the hot water bottle should retain the heat for as long as possible. Unfortunately, it sometimes cools down faster than you'd like. But there is a simple trick to extend the heat storage of the hot water bottle. The material used in the hot water bottle plays a decisive role in this.
Not all hot water bottles are the same: what you should pay attention to
When searching for hot water bottles on the Internet, you will mainly come across models made of PVC or rubber. The difference in material can be the reason why your hot water bottle loses heat quickly.
Hot water bottles should be replaced every three to five years or so. © Jochen Tack/Imago
Hot water bottles made of rubber – usually rubber – feel pleasant on the skin. However, they quickly lose their heat. In addition, the rubber hot water bottles become porous over time and can smell unpleasant.
PVC hot water bottles, on the other hand, are more robust than their rubber counterparts. They are odourless and retain heat longer. However, caution should be exercised when buying, as cheap PVC products may contain harmful substances.
Grandma's trick for long-lasting warmth in the hot water bottle: A spoonful of salt
If not handled properly, hot water bottles can be dangerous. You should avoid using boiling water – temperatures of 40 to 60 degrees are usually sufficient. In addition, hot water bottles should only be filled to two-thirds of their volume to prevent possible bursting. And a hot water bottle cover or towel protects against possible burns.
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Fancy a voyage of discovery?
Usually, a hot water bottle will keep you warm for about an hour before it slowly cools down. To extend this window, add a spoonful of salt to the water before heating. The trick is that salt water has a higher heat capacity and thus retains heat longer. By the way: Salt has a similar effect on tea lights. Simply sprinkle a little salt into the already liquefied wax around the wick. This allows the candle to burn up to 25 percent longer. (ls)