Short answers, pulled from the story.
Sublimation is the direct transition of a substance from the solid phase to the gas phase, bypassing the liquid state entirely. It is an endothermic process driven by heat absorption, and the energy required is quantified as the enthalpy of sublimation, which equals the sum of the enthalpy of fusion and the enthalpy of vaporization.
Dry ice (solid carbon dioxide) is one of the most familiar examples, subliming at -78.5 degrees Celsius at atmospheric pressure. Naphthalene in mothballs and the gradual disappearance of snow or ice during cold weather are also everyday examples of sublimation.
Dry ice sublimes at -78.5 degrees Celsius at atmospheric pressure. Its triple point, the minimum pressure at which liquid carbon dioxide can exist, sits at 5.1 atmospheres and -56.6 degrees Celsius.
A solid compound is placed in a sublimation apparatus and heated under vacuum, causing it to volatilize and condense as a purified substance on a cooled surface called a cold finger, while non-volatile impurities remain behind. For higher purity, a temperature gradient is applied along an evacuated glass tube to separate compounds by volatility. This method achieves purities exceeding 99.99 percent, making it the standard technique for organic electronics manufacturing.
Sublimation dyes are first transferred to transfer paper via liquid gel ink through a piezoelectric print head. The paper is then pressed against a polymer-coated substrate using heat and pressure, with most dyes activating at 175 degrees Celsius. Because the dyes infuse into the substrate at the molecular level, the resulting prints do not crack, fade, or peel under normal conditions.
Alchemists used sublimation to describe heating a substance until it rose as vapor and condensed on the upper portion of a retort or alembic. Authors including Basil Valentine and George Ripley treated it as a necessary step in completing the magnum opus. Valentine's work Le char triomphal de l'antimoine, published in 1646, compared laboratory sublimation to vegetable sublimation used to separate spirits in wine and beer.