Litmus is a solution primarily used to indicate the acidity and alkalinity of a liquid, known as the ph. The ph value of a sour beer is often 3.5 or lower turning the paper towards the red colour scale. A clean, refreshing and tart kettle sour fermented with kilo upon kilo of raspberry and lime. Expect a citric tartness, with a soft berry sweetness, and a backbone of wheat. Perfect summer sipping.