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

"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

Thanks for the info Lum.

Let me see if I understand what you are saying:

The bound SO2 is pretty well irrelevant to wine protection. It is the
Moleclar SO2, present in the Free SO2, that does the protecting.

The Molecular SO2 that is required to protect is based on the PH and
this gives you the free SO2 level that you should be aiming for.

Thanks

AB1

"Lum" > wrote in message >...
> "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

"ab" > wrote in message
om...
> Thanks for the info Lum.
>
> Let me see if I understand what you are saying:
>
> The bound SO2 is pretty well irrelevant to wine protection. It is the
> Moleclar SO2, present in the Free SO2, that does the protecting.
>
> The Molecular SO2 that is required to protect is based on the PH and
> this gives you the free SO2 level that you should be aiming for.
>
> Thanks
>
> AB1

You have it right AB1.
lum

"ab" > wrote in message
om...
> Let me see if I understand what you are saying:
>
> The bound SO2 is pretty well irrelevant to wine protection. It is the
> Moleclar SO2, present in the Free SO2, that does the protecting.

That's pretty close.

> The Molecular SO2 that is required to protect is based on the PH and
> this gives you the free SO2 level that you should be aiming for.

Not quite. The amount of molecular SO2 needed to protect the wine is
constant at about 0.8 ppm. The amount of free SO2 required to produce 0.8
ppm molecular SO2 depends on the pH. If the pH is 3.2 e.g., it takes about
20 ppm free SO2 to produce the "magic" 0.8 ppm molecular SO2. If the pH is
3.6, it takes closer to 60 ppm free SO2 to produce 0.8 ppm molecular SO2.

A good rule of thumb is to set the free SO2 to the two digits to the right
of the decimal of the pH. IOW, at pH 3.50, set the free SO2 to 50 ppm; at
pH 3.35, set it at 35 ppm, etc. That'll get you pretty close for wines in
the normal pH range, and it's easy to remember.

Tom S

Many Thanks

AB1

"Tom S" > wrote in message . com>...
> "ab" > wrote in message
> om...
> > Let me see if I understand what you are saying:
> >
> > The bound SO2 is pretty well irrelevant to wine protection. It is the
> > Moleclar SO2, present in the Free SO2, that does the protecting.
>
> That's pretty close.
>
> > The Molecular SO2 that is required to protect is based on the PH and
> > this gives you the free SO2 level that you should be aiming for.
>
> Not quite. The amount of molecular SO2 needed to protect the wine is
> constant at about 0.8 ppm. The amount of free SO2 required to produce 0.8
> ppm molecular SO2 depends on the pH. If the pH is 3.2 e.g., it takes about
> 20 ppm free SO2 to produce the "magic" 0.8 ppm molecular SO2. If the pH is
> 3.6, it takes closer to 60 ppm free SO2 to produce 0.8 ppm molecular SO2.
>
> A good rule of thumb is to set the free SO2 to the two digits to the right
> of the decimal of the pH. IOW, at pH 3.50, set the free SO2 to 50 ppm; at
> pH 3.35, set it at 35 ppm, etc. That'll get you pretty close for wines in
> the normal pH range, and it's easy to remember.
>
> Tom S

AB1,

You may also find the following article helpful:

http://members.tripod.com/~BRotter/SO2.htm

Ben