Filtering Experiment – can you do better?

We’ve tried a filtering experiment using dirty water before, using kitchen roll as the filter. Today we tried something a little different.

We looked in the garden for three things that might make good filters, and chose large stones, small stones and sand. We talked about which we though would be the best filter, and decided the sand would probably work best as it was the smallest.

Filtering Experiment

What you need

  • Large stones
  • Small Stones
  • Sand
  • Containers
  • Funnel
  • Dirty water – we just added some soil from the garden to some tap water.

filtering experiment


  • Place the large stones in the funnel and hold it over a container, pour the water through.
  • Add the small stones to the top of the large stones and repeat, does the water look clearer?
  • Add the sand and repeat again.


Our results were not as clear as I had hoped. You can see that the water filtered by all three materials is slightly clearer than the first two, but some sand seems to have dropped through the funnel.


filtering experiment



How to improve

We need to use a bigger funnel so we can have more of each material to make the filtering is better. This should also stop the sand dropping through into the water.

Do let us know if you try a filtering experiment yourself, we’d love to hear about how you got on.

Suitable for Key stage 2 Science

Properties and Changes of Materials

Use knowledge of solids, liquids and gases to decide how mixtures might be separated, including through filtering, sieving and evaporating.

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