After engraving images into crystals by our laser subsurface engraving machine.the engraved crystals will be put in a special oven machanism, with different tempreture setting, the exploded design will change color as the ingredients inside the crystal material reacts with the tempreture changes. I am Michelle, for detail information, please send letter to sales4(at)leadlaser.com, it is also my MSN ID, and my skype ID is leadlaser4. any enquiries will be highly appreciated. Best regards