Anyway, now it is time for a little experiment - making mead liquor. From Wikipedia I found a graph under ethanol relating alcohol percentage vs temperature. Notice that the Ethanol content is in % by mass.
Converting is easy: 15.0% by volume in 1 L is 150ml Ethanol/1000ml total volume. 150ml of ethanol weighs 150ml x 0.789g/ml = 118.35g. The 1000ml-150ml = 850ml of water weighs 850ml x 0,998207g/ml (at 20C) = 848.48g. Total mass is 118,35g + 848,48g = 966,83g, so ethanol % (m/m) or wt% is 118,35g/966,83g = 12.24% ~ 12.2%
Now, your common household freezer should cool to about -20C. During the freezing only (mainly) water crystals are formed, so basically the the remaining liquid should not freeze when the alcohol percentage reaches 30% (m/m). This means that if my mead is 15% by volume which corresponds to 12.2% by mass, I should be able to reduce the water ideally by a factor of 2.46, i.e. reduce 1000 ml to 407 ml which is 35.2% by volume or 30% by mass as indicated by the graph.
Realistically I will be happy reducing the volume to about half. Starting with 15% by volume and loosing a bit to the frozen water phase I guess I would likely end up with 25%-28% by volume or 20.9%-23.5% by mass.
So now for the experiment: I have gotten my hand on an old beat up magnetic stirrer which only works at a very little speed range. Never the less the speed was adequate for the experiment. I placed the stirrer in my freezer with the wire hanging out hoping not to stretch the insulation in the door. A beaker with 200 ml and a magnet was placed on top of the stirrer together with a glass bowl of the beaker should break. The beaker was covered with plastic foil as lid. When the magnet was stirring the mead adequately, it was time to wait.
After about 6 hours (probably ready earlier but that was when I got home), the mead had turned into a thick slurry but the magnet was still moving. The ice consisted of quite small crystals which was great since the smaller the crystals, the smaller the change of trapping the ethanol within the ice.
To remove the ice I simple poured the entire content of the beaker into a kitchen sieve, held over a bowl. Shaking the sieve and letting it drip for a short while would melt some of the ice but also remove most of the ethanol. The ice layer was then removed and the liquid collected in the bowl was poured back into the beaker with the magnet and placed in the freezer once again. The volume had been reduced to less than 150 ml
4 hours later the process was repeated. The volume of ice was now significantly reduce, and was removed in the same manner. The volume was now about 100ml.
I had reached my target but I got a bit greedy and figured I would go for the 3 freezing cycle. But after about 3 hours only a little ice was circulating in the beaker, and pouring it into the sieve, the ice melted too quickly to be collected. (I should perhaps have cooled the sieve in the freezer too). I decided to stop here and collect my mead liquor and the removed water. Liquor to the left, residual water to the right :o)
I feel comfortable that it is time to scale up the procedure to a 1 L of mead with the target of collecting 0.5L of mead liquor :o)
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