hist-brewing: Brandy and fortified wines

Sean Richens srichens at sprint.ca
Fri Sep 22 16:49:16 PDT 2000


Jeff Renner provides a valuable service in demonstrating how the answer you
get depends on the professional biases of the "expert" you ask.

Being a chemical engineer, I favour the mass transfer explanation:

> "Yet another noted distiller suggested that the year-round humidity
> of Scotland favored the proportionately greater evaporation rate of
> alcohol there, whereas the relatively less humid climate of Kentucky
> (especially in the upper floors of the warehouses in the hot summer
> time) favors a relatively greater rate of evaporation for water.

It's the same principle behind why the pressure of CO2 in a bottle of beer
doesn't keep oxygen from diffusing in through permeable plastics or cap
seals.  I don't blame the people Jeff surveyed for not thinking of it, I
didn't think of it either until I read it.

All of the other answers don't quite pass the BS test, in my arrogant
opinion.  There are osmotic processes for removing alcohol from beer etc.,
but if wood did the job there would be all sorts of folk recipes for making
applejack by aging in barrels.  Relative volatility of solvent pairs can
vary with temperature, but in 99.9999% of cases, not very much.

Sean



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