Polishing the crystals to make them optically cleaner would be a good next step, as would perhaps growing even larger crystals.

Borax makes it easy for your kids to experiment and grow crystals of their very own! Let’s experiment for Valentine’s Day and make heart crystals Gather your kids around the table for this fun ...

They arranged dozens of red Solo and clear plastic cups, each containing one alum crystal, on the room’s large wooden table.