"ab" > wrote in message
om...
> Can someone please explain to me, in easy to understand terms, the
> relationship between bound and free SO2?
>
> Does the bound SO2 dissipate over time and any free SO2 then start to
> bind to the wine?
>
> I ask because I have a wine which was over sulphered last year and I
> have been monitoring the free and bound SO2 over the past few months.
> The bound SO2 is quite high (around 80ppm) and the free is down to
> below 10pmm.
>
> I am wondering if I should add more SO2 as the free is recommended to
> be at around 20-30ppm.
>
> Any advice / help would be greatfully accepted
>
> AB1


AB1,

Measuring bound SO2 is difficult. So, I assume you are measuring "free" and
"total" SO2 and subtracting the free from the total to get a value for bound
SO2.

Free SO2 drops slowly over time as some of the free SO2 is blown off as gas,
some becomes combined with other wine components and some is converted into
sulfuric acid.

Bound SO2 increases slowly. But, the increase in bound SO2 becomes slower
and slower as Free SO2 combines with other wine components.

The SO2 levels in a typical, year-old, red wine might be 100 PPM total SO2
and 25 PPM free SO2 at bottling time.

80 PPM of bound SO2 is a reasonable value if you wine is ready to bottle. I
would measure the pH of the wine and adjust the free SO2 to about 0.8 PPM
molecular and bottle. More info here
http://home.att.net/~lumeisenman/chapt6.html

lum