Making Salt

Evaporation: Separating Salt From Seawater


As part of my project studying rivers, I have been looking at the water cycle.

Part of the water cycle is evaporation, so for this experiment I turned some seawater into salt.

As the water evaporated the salt that had been in the water was left.

Read on to see how I made my own sea salt…

Stage One: Collecting The Seawater

I went to my favourite beach and filled a 750ml bottle with seawater. 

I got quite wet!!!


Stage Two: Filtering The Water

To get the purest salt possible, we filtered the seawater through a Liz Earle muslin cloth (over the years we have found MANY uses for these, from dolls house curtains to making jams and jellies!)

This got rid of bits of seaweed and grains of sand.


Stage Three: Heating The Seawater

To speed up the process of evaporation, we heated it up in a saucepan until almost all the water had gone. We then finished the evaporation on a baking tray in the oven.

While the water was bubbling away I saw loads of steam rising.

This is exactly the same as what happens when the sun heats the sea and the water vapour forms clouds.

I learned that a liquid can be turned into a gas when it’s heated and that the gas can then return to its liquid form when cooled. This steamed up the windows in our kitchen when the steam hit the cold glass. This is called condensation.

Seawater isn’t just water. It also contains quite a lot of salt that’s dissolved in it. When the water evaporates the salt is left behind.


Stage Four: Finishing The Sea Salt

I broke up the solid cake of salt by hand and then put it in a mortar and pestle, grinding until it had become a fine powder.

Here’s an interesting fact: from our 750ml of seawater we made 25g of sea salt. This means there is 1g of salt in every 30ml of water. That’s much more than I thought!

We all tasted it – it was ABSOLUTELY DISGUSTING!!! But it did taste like salt – success!

  1. Great fun experiment ⏳

  2. Impressive!!!

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