Here's a project where Rochelle salt can be crystallized to get a piezo effect. http://srjcstaff.santarosa.edu/~yataiiya/E45/PROJECTS/Homebrew%20Piezoelectric

Here's a project where Rochelle salt can be crystallized to get a piezo effect. http://srjcstaff.santarosa.edu/~yataiiya/E45/PROJECTS/Homebrew%20Piezoelectric%20Crystal.pdf http://srjcstaff.santarosa.edu/~yataiiya/E45/PROJECTS/Homebr... The sodium carbonate needed is otherwise known as "washing soda" in addition to being called "soda ash".