VEVOR HFD-4 Bedienungsanleitung Seite 9

2.vacuum freeze-drying process
Freezing: Under normal atmospheric pressure, reduce temperature to
freezing to ice structure
Drying: Under certain vacuum, such as 1pa, and keep the water in solid
phase.
Energy input: heating, keeping some matter in solid phase. The matter's
temperature is controlled by certain vacuum.
3.Pre freezing
The sample could be pre freezing in freezing dryer. It's thickness should no
more than 1~2cm. Otherwise it should extend Freeze drying time.
4.Main drying
Open the vacuum pump, create a vacuum environment, causing
sublimation.
Warning：
The substance of the acid or any other substance containing corrosive

volatile solvents should not be dried with this machine.
Pay special attention to azides cannot be used, because it combines

with copper or other nonferrous metals will explode.
As soon as the water begins to sublimate, it absorbs heat and causes

the temperature to drop.
The pressure in the drying chamber increases with the sublimation and

must be reduced by the condenser.
The duration of the main drying process is mainly determined by:
（1）Sample's thickness
（2）Energy to sample when drying process
（3）The chamber's pressure when drying process
Increasing chamber's pressure, could increase the rate of sublimation and
shorten the drying period.
- 7 -