A volumetric glassware calibration procedure checks how much liquid a flask contains or a pipette or burette delivers. The common gravimetric method weighs purified water at a measured temperature, converts that mass to volume, and compares the result with an approved requirement. The weighing step is simple. Getting a defensible result takes more care. You

TL;DR: When Do You Need Glass? Use glass when your work involves heat, strong solvents, tight volume accuracy, or contamination-sensitive measurements. Glass is also “mandatory” any time your SOP, method, or regulator calls for it. Plastic is great for sterile, disposable, low-risk steps, but it can warp with heat, absorb chemicals, or add trace contaminants.