43. Congelation original: "Congelatio". In alchemy, this is the process where a liquid substance is transformed into a solid, often through cooling or the joining of chemical opposites.

An illustration in monochromatic ink and wash shows an alchemical operation. At the top, a decorative banner displays the number 43 and the title Congelation. Below the banner, there is a large, transparent glass flask with a rounded body and a narrow, capped neck. Inside the flask, an Ouroboros (a serpent biting its own tail) forms a circle. This serpent surrounds a dark, shaded sphere at the bottom of the vessel. The sphere has wavy textures to represent matter as it undergoes transformation.