Hard water, soft water – does it matter?

close up of soap bubbles

Have you ever seen white spots forming on bathroom or kitchen faucets? They come from minerals dissolved in the tap water. When the water evaporates, the minerals are left behind. We also speak of lime stains as well as calciferous or hard water. Water with little lime is called soft water. So-called distilled water contains no lime or other minerals at all.

Lime stains are only one side effect of hard water. Water hardness also affects every washing process – whether it's doing laundry, washing dishes or washing hair. This is because the lime in the water reacts with the cleansing substances, the surfactants. The effects can also be seen in the foam: the harder the water, the less foam.

We investigate this with a simple experiment.

You will need

  • Empty plastic bottles
  • Tap water
  • Distilled water* 
  • Measuring cup
  • Bottled water with high calcium content
  • A teaspoonful of dishwashing detergent or shampoo 

* from the supermarket

Let’s get started!

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