Coaxing crystals large enough to see, like the ones on our crystalline growlers, is a very scientific firing process. Invisible crystals exist in most glazes, but to grow larger crystals requires a bit of a "perfect storm." You need a precise ratio of ingredients, and the firing needs to be held at a specific temperature for an extended period of time, or the crystals won't form. 
Crystals grow on a molecular level, so the size and quantity of the crystals are beyond our control, but we create an environment that’s conducive to crystal formation. The process is actually called "seeding crystals," so you can think of it like you might think of gardening: no two plants, flowers or vegetables look exactly the same and neither do our Crystalline growlers. They are truly a functional work of art.
Each Crystalline growler comes with a custom PGC flip top lid. Please allow up to two weeks for completion and shipment of crystalline growlers.