All kits use absorbance spectroscopy, which works within a linear concentration range. When absorbance approaches 1.8 AU, results become non-linear and signal is lost in noise — meaning dilution is required.
During vintage, analytes such as:
May exceed the measurable range.
General guidance:
Red wines rarely need decolourisation. PVPP can be used if required, but dilution is usually sufficient.
Grape juice, ferments and finished wines can all be tested — with correct preparation.
