Hard water testing method

Equipment list

Measuring cylinder (10ml, 50ml)
Boiling tubes
Bungs to fit boiling tube
Soap solution
Selection of waters to test.


Measure out 25ml of water to be tested and pour into the boiling tube.
Measure out 2ml of soap solution and add to the boiling tube.
Insert the bung and put your thumb over the top.
Use the stopclock to time vigorously shaking the tube for 15 seconds.
Place the tube into the rack and note the height of the foam formed from the water surface to the top of the lather.
Repeat three times for each water sample to find a mean.


Ensure the bung does not slip out during the shaking. This could go into the eyes or could leave a slip hazard. Should any tubes be droped and broken any spills should be cleared up straight away.


The hardest water should produce the least bubbles and also produce a soap scum (Calcium Stearate).