In the United Kingdom, freeze-drying flowers is a distinctive method for preserving floral arrangements. This technique is employed by a small number of preservation artists due to the necessity of specialised machinery. 

**Understanding Freeze-Drying: The Process of Sublimation** 

The freeze-drying process begins with placing your flowers in a freezer, initiating their transformation. Subsequently, the flowers are moved to a specialised freeze dryer, where temperatures drop to approximately -40 degrees Celsius. This critical step turns the flowers' moisture to ice, helping to maintain their natural beauty. 

Once frozen, a vacuum is applied to drastically lower the pressure within the chamber. This low-pressure environment facilitates sublimation, allowing the frozen moisture to transform directly into vapour without entering a liquid state. This crucial phase safeguards the flowers' shape and vibrant colours. 

As the process advances, controlled heat is introduced to encourage sublimation, directing the vapour into a cooler section of the chamber where it refreezes and crystallises back into ice. This careful method captures the flowers' essence, ensuring their beauty is retained in the final preserved form. 

Once the cycle is finished your flowers are taken out of the freeze dryer and are ready to be placed in your chosen preservation items.