Get your starter. The starter's job is to provide acetic acid bacteria, which converts ethanol into acetic acid (the primary ingredient in vinegar). Unpasteurized, unfiltered vinegar. It's important to use vinegar that hasn't been processed in a way that interferes with the acetic acid bacteria. Mother of vinegar.
Pupillary distance. Pupillary distance (PD) or interpupillary distance (IPD) is the distance (the industry standard is to measure in millimeters) between the centers of the pupils in each eye. This measurement is used when preparing to make prescription eyeglasses.
What is a PD value? Great question! Your PD (pupillary distance) measures the distance from the center of one pupil to the other pupil in millimeters. This can equal one number if the left and right side have been added together or two numbers if the left and right side differ. pd value examples: 63 or 31/32.