1/2 L of swamp water (or tap water with mud or dirt added)
2 L soda pop bottle with its lid
2 L plastic soda pop bottle—cut in half (have an adult help with cutting)
1000 ml beaker
2 20 oz cups
1 tbsp alum (aluminum potassium sulfate)
2 c fine sand
1 c coarse sand
1 c small pebbles
1 filter paper or coffee filter
1 rubber band
1 large spoon for stirring
spoon for scooping the alum
stopwatch or timer