What is the Kyropoulos (KY) growth method?

“The Kyropoulos method grows large sapphire crystals by slowly cooling a molten alumina bath around a seed crystal. It produces some of the largest and highest-purity sapphire boules available — Falcon Sapphire produces boules of 100+ kg with exceptional optical homogeneity and minimal structural defects. KY is considered the leading method for demanding optical and precision applications.”