7. Freeze-drying Multifibre 6 of experiment 1 (Gravimetry) Washed fabrics will dry at temperatures below zero. The direct transformation of ice (solid water) into water vapour is industrially used to produce instant coffee: In a first step brewed coffee is deep frozen, then in a vacuum chamber at a temperature of micus 70° the ice directly changes into water vapour.
You will do a freeze drying at normal air pressure. This will take time. Nevertheless you will achieve the direct transformation of frozen water from the fabric to vapour by repeating experiment 5 in a deep-freeze.
To find out how fast this low-cost freeze drying works, balance the frozen fabric on the scale, return it  into the deep-freeze and reweigh every six or twelve hours until the fabric is dry again.
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Materials
like in experiment 3, deep-freeze.
Experiment
like in experiment 3. Between two weighings keep everything (including the scale) in the deep-freeze.
Observations
1. After 6 hours in the deep-freeze (Fig. 1) the fabric has clearly lost weight (Fig. 2).
2. After one week the frozen water in the fabric has been reduced from 2 g (mL) 0.4 g.
Explanation
The process in which solid water is directly transferred into water vapour is called sublimation.

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