"Rich" > wrote in message
om...
> The few books I looked at all seem to guess when
> fermentatiopn is done, cannot you use a stable SG as a sign that it is
> done?
No, because a stable SG just means that the yeast are not fermenting
anymore. This can have a number of causes, one of which is that there is no
sugar left, which is obviously the most desirable one.
Also, once there is only a small amount of sugar left, it is almost
impossible to detect changes in sugar level by SG measurements. If any sugar
is left, spoilage bacteria can rapidly convert even the smallest amount of
sugar into some fairly unpleasant flavours. Unfortunately, expensive
enzymatic or HPLC methods are the only sure way of telling there is no sugar
left. But you can go a fair way using Clinitest or some chemical methods.

Cheers,

Andrew