"Marty Phee" > wrote in message
...
> That's the problem I have with both books I got. They both assume your
> starting from freshly crushed grapes.
>
> For instance my juice can already with sulfites added (100ppm) and if I
> were to add more according to the books I'd run the chance of ruining it I
> believe.

If you already have 100 ppm SO2 in there you won't need to add any until
fermentation is complete - and probably not much then. You will need to be
able to measure the free SO2 then to tell.

Tom S