The "Binding" Problem
When you add sulfite to your wine, you aren't just adding a protective blanket. A large portion of that addition reacts with chemical compounds and solids naturally present in your wine. It becomes "bound" and is no longer actively protecting your wine.
The only thing keeping your wine safe from oxidation and microbial spoilage is the "Free SO₂" that remains.
The pH Connection
The amount of Free SO₂ you need is not a fixed, one-size-fits-all number. It is entirely dependent on your wine's pH. For example, a wine sitting at pH 3.6 needs roughly 50 ppm of free SO₂ to stay protected. That exact same wine at pH 3.2 needs less than half that amount.
If you don't know your pH, you cannot accurately protect your wine.
Pro-Level Accuracy
The Tool We Use to Measure It
To actually use the dosage chart in the guide, you need two highly accurate numbers: your current pH and your current Free SO₂.
Titrets and cheap test strips might be okay for a quick check, but if you are making larger volumes that represent a significant investment of your time and money, you need real data.
That is why we use and recommend the Vinmetrica SC-300.
It tests Free SO₂, pH, and TA in one single instrument. This is crucial because you need both the pH and the SO₂ numbers to dose correctly. It is highly accurate, straightforward to use, and built specifically for home winemakers who take their craft seriously. Once you use it a few times, it becomes as routine as floating your hydrometer.
