"Beege" > wrote in message
...
> I think that if you added something to kill of unwanted bacteria and
yeasts
> at the beginning, that if you add yeast right away, it would die, too. The
> 12 hours is to wait for the effects of the drug to wear off?
>
> Beege

Beege,
Here is how sulfur dioxide works. Most winemakers add an initial dose of 30
to 50 ppm of sulfur dioxide when grapes are crushed to help control native
yeast. Contrary to much home winemaking literature, sulfur dioxide added at
crush does not kill native yeast, but it does greatly diminish their
activity for several hours. Commercial wine yeast has considerable
tolerance to sulfur dioxide and remains active in the presence of normal
amounts of sulfur dioxide. When commercial yeast is added to juice
containing reasonable amounts of SO2, a large population of the added yeast
quickly develops while the native yeast is inactive. The commercial yeast
then dominates the fermentation, and this is why all wine yeast
manufacturers recommend adding yeast immediately after sulfur dioxide
additions.

Lum
Del Mar, California, USA