3.5. Observation of sublimation interface
Partially freeze-dried specimens were taken from the dryer, and their cutting surfaces were observed and sketched. Observations were quickly carried out on the various cross sectional cuts with numbers of specimens, and the results were summarized in a sketch. Based on the sketches, 3D images of the frozen fractions were redrawn with CAD software (AUTODESK, 123D Design 21.1.5). The volume of the frozen fraction, VffVff, and the corresponding surface areas of the frozen layer in contact with the sample tray, AbtmAbtm, and the sublimation interface, AsAs, were estimated using this software.