Cleaning volumetric glassware without destroying its calibration
Care & Use · 6 min read · Vitreon technical desk
Chromic acid is obsolete, dishwashers are riskier than they look, and a 300 °C drying oven will quietly re-anneal your tolerances away.
01The cardinal rule: no heat
Volumetric glassware is calibrated at a reference temperature. Drying above 150 °C relaxes the glass enough to shift volume measurably — a Class A flask dried at 300 °C repeatedly can drift outside tolerance. Air-dry volumetric ware, or use a drying cabinet below 60 °C. Ovens are for beakers.
02Daily cleaning
Warm laboratory detergent solution immediately after use, before residues dry. A water-break test tells you when you are done: pour water down the wall — if it sheets evenly without beading, the surface is grease-free and your meniscus will sit true.
03Stubborn residues
Alkaline lab cleaners (short contact, rinse thoroughly — see our compatibility checker) handle grease; dilute nitric or hydrochloric acid handles metal deposits and water stain. Chromic acid mixtures are effective but carcinogenic and environmentally banned in most jurisdictions — modern peroxydisulfate cleaners match them without the chromium.
04PTFE stopcocks
Never soak assembled PTFE keys in strong alkali — the barrel etches microscopically and the key seizes. Disassemble, clean parts separately, reassemble finger-tight. No grease, ever: grease is a contamination source and PTFE does not need it.