Or, rub them together outside the pail and insert them separately and together. Rub a rod with a cloth, place on a pivot, show attraction between rod and cloth. A glass tube containing some mercury is covered with tin foil on one end. Either positive or negative charge may be produced. 5A10.43 mercury tube E-20 Directions for making a mercury tube that emits light when shaken.
Optionally neon is introduced to produce more light.
The polarization of some pyroelectric crystals increases dramatically at low temperatures. Heat a long thin crystal of tourmaline over a flame and when it cools opposite charges develop on the ends large enough to deflect an electroscope. E-190 A long thin crystal of tourmaline that has been immersed in liquid air will form opposite charges on the ends upon warming. E-22 Allow molten sulfur to solidify on a glass rod, check with an electroscope. E-19 A stretched rubber band becomes charged positively.