hist-brewing: Re: distillation

[PBLoomis at aol.com]

In a message dated 7/29/2003 9:22:39 PM Eastern Standard Time, 
burningb at burningbridges.com writes:

> Methyl alcohol (aka wood alcohol, methanol)
> actually has a lower boiling point than ethyl alcohol, 148F I think, and
> will come over _first_ in a column still.  Indeed the fusel oil components,
> chiefly amyl alcohol, have higher boiling points. That brings up another
> issue, though.  If you exclude the undesirable higher boiling components
> like amyl alcohol via rigorous fractional distillation, you are also
> excluding the flavor and aroma components (mostly heavier esters and ethers)
> that you _want_ to have in the final product.  You just end up with nearly
> pure ethyl alcohol/water azeotrope with little flavor-- not a very desirable
> product. The point is moot though. Stills capable of precise fractionation
> like this are recent inventions.  In medieval times they were not just
> unknown, but people wouldn't have understood them. The stills they used (and
> are still used for many liquours) for the various national forms of aqua
> vitae were simple pot stills called "alambics" I believe: different
> components did not separate into precise fractions at precise temperatures,
> rather the temperature of the distillate vapor rose in a continous curve.
> They weren't capable of eliminating the contaminants you mention.  And
> because they weren't, while these stills are not nearly as efficient as
> modern column stills and don't yield everclear strength distillate without
> several redistillation steps, they do possess one enormous advantage over
> fractionating stills:  the esters involved in imparting a flavor are carried
> over with the ethanol-enriched steam into the condenser, and thus into the
> product.  It's the same principle used in steam distillation, widely used to
> extract essential oils from herbs.  Modern fractionating stills will not
> achieve that result; their only usage is to separate the undesirable
> chemicals mentioned earlier, but honestly if you question drinking something
> in its raw state then why on earth would you consider consuming its
> distillate?
> 
       I believe the Bain Marie, or water jacket, around an alembic is 
pre-1600.
       Scotti
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