What about the Archimedes principle?
Harder soaps will be denser. Thus, if you add identical masses of different soaps to a full bath, you can calculate density by the amount of water which spills into the flat below you.
An added benefit is that you can quickly detect gold and other precious metals which are often hidden in croap.
Harder soaps will be denser. Thus, if you add identical masses of different soaps to a full bath, you can calculate density by the amount of water which spills into the flat below you.
An added benefit is that you can quickly detect gold and other precious metals which are often hidden in croap.