Use buffer solutions to keep your pH meter calibrated. These are the same 3 solution powders that are included with the Beverage Doctor pen-style pH meter.   We would strongly recommend if you haven't used your Beverage Doctor in a while to always use a buffer solution before you start your brew.

• Completely empty the powder into a clean 250mL glass beaker
• Add 250mL of deinoized water to the beaker
• Stir until the powder has completely dissolved