Vac Ovens, Vacuum chambers
Their only purpose it to make the shatter! To harden and cure your essential oil!
Like sugar in candy making depending on the temperature you bring it up to its consistency changes with heat and pressure. low heat makes a sauce more heat makes a caramel more heat make taffy and with enough heat you can make suckers and rock candy! With to much heat you scorch it!
Essential oil works in basically the same manner.