Technical Guides/Care and cleaning

Practical

Care, cleaning and safe handling

Good borosilicate glassware lasts decades. Most of it does not, and the reasons are almost always avoidable: the wrong cleaning bath, an unsupported clamp, or heat applied too fast.

Interactive

What are you trying to remove?

Pick a residue and get the method that works on it — and the one that will ruin the glass.

Recommended method

 

General guidance for borosilicate 3.3 laboratory glassware. It does not replace the safety data sheet for whatever you are removing, or your own institution's rules. Always work in a fume hood with appropriate protection when handling concentrated acids or solvents.

The routine

Everyday cleaning

  1. Rinse immediately after useAlmost everything comes off easily while it is still wet. Once a residue dries onto glass it becomes a different, much harder problem.
  2. Wash with a laboratory detergentWarm water and a non-abrasive lab detergent, with a soft brush. Never scouring powder, never steel wool — scratches become stress concentrators and stress concentrators become cracks.
  3. Rinse with tap water, then distilledThree or four tap rinses to clear the detergent, then a final rinse with distilled or deionised water so nothing is left behind as it dries.
  4. Dry inverted, or in a drying ovenAir-dry on a rack or peg board. If you use an oven, keep it well below 150 °C for volumetric glassware — heat changes calibrated volumes permanently.

The test for clean. Water should sheet evenly off the inner surface with no droplets clinging. Beading means an oily film is still there, whatever the glass looks like.

Do

  • Support glassware at two points when clamping anything heavy
  • Let joints cool before trying to separate them
  • Use a PTFE sleeve when grease would contaminate the reaction
  • Inspect for star cracks and scratches before applying vacuum
  • Store ground joints assembled and lightly greased, or capped
  • Heat and cool through a bath or mantle, not a naked flame

Do not

  • Leave glassware soaking in a strong alkaline bath overnight
  • Put ground joints, frits or volumetric ware in a base bath at all
  • Clamp glass directly against bare metal
  • Apply vacuum to flat-bottomed or scratched vessels
  • Use a chipped or star-cracked piece, however small the flaw
  • Cool a hot flask by running cold water over it
THE FLAW THAT MATTERS A star crack radiating from an impact point.

Before you pull vacuum

Inspect, every time

A vessel under vacuum holds roughly 10 tonnes of force per square metre pressing inward. Sound glass carries that easily. Flawed glass does not, and it fails without warning, inward, sending fragments in every direction.

Hold the piece up to a good light and turn it slowly. You are looking for:

  • Star cracks — the radiating pattern above, usually from a knock against a tap or a clamp. Any piece with one is finished.
  • Scratches — particularly deep ones running around a flask, the classic legacy of an abrasive cleaner or a wire brush.
  • Chips at the rim or joint — small ones can sometimes be fire-polished by a glassblower, but not by you.
  • Frosted or etched patches — the signature of alkali or HF attack, and a sign the wall is thinner than it looks.
  • Strain — visible as coloured fringes through crossed polarising filters. Poorly annealed or locally overheated glass carries stress even when it looks perfect.

Never apply vacuum to flat-bottomed glassware. Erlenmeyer flasks, beakers and media bottles are not designed for it. Use a round-bottom flask, a proper filter flask, or a vessel explicitly rated for vacuum — and shield it.

Specific items

Things that need their own rules

Sintered filters and frits

Wash a new frit with dilute hydrochloric acid and rinse thoroughly before first use, to clear loose glass dust from manufacturing. Always clean by back-flushing from the stem side — rinsing from the top drives residue deeper into the channels, where it sets and permanently reduces flow. Never put a frit in a base bath: hot alkali widens the pores and the disc quietly stops meeting its grade. There is more detail in the porosity guide.

Clean grease off with a solvent appropriate to the grease type before washing, or the detergent will simply smear it around. Do not use abrasives on a ground surface, and keep joints out of alkaline baths, which dull the grind and spoil the fit. Store long-term with the joint assembled and lightly greased, or capped, so nothing settles on the ground zone. See the joints guide for greasing and freeing seized joints.

Calibrated volumes are only valid at the stated temperature, and heat changes them permanently. Keep volumetric flasks, pipettes and burettes out of drying ovens above about 150 °C, and never flame them. Clean with detergent, and let them drain dry rather than forcing them. If the water does not sheet evenly down the inside wall, the calibration cannot be trusted either.

Disassemble PTFE stopcocks for cleaning and store them loosened, not tightened — PTFE creeps under sustained load and a plug left clamped tight will deform. Glass stopcock plugs must stay with their own barrel; they are ground as a matched pair and are not interchangeable between valves. Keep O-rings out of solvents they are not rated for; the glass will be fine, the elastomer will not.

Always keep a Dewar in its protective mesh or housing. The vacuum jacket means a failure is an implosion, not a crack. Inspect for any loss of silvering or clouding between the walls, which indicates the vacuum is going. Cool slowly by adding cryogen in stages rather than filling in one pour.

Store on padded shelves, not stacked, and never rim-down on a hard surface. Keep pieces from touching each other — glass against glass during a knock is how chips start. Long items such as condensers and columns should lie supported along their length or hang vertically, not bridge a gap between two points.

Replacing something

If a piece is past saving

Cracked, chipped or etched glassware is not worth the risk. The Synthware range covers the standard sizes.

Browse the full range Ask us what fits
Guide

Filter porosity

Choosing between P0 and P5, with a filtration simulator.

Read the guide
Guide

Ground glass joints

What 24/40 and 29/32 mean, and which fit together.

Read the guide
Material

Borosilicate 3.3

The properties behind the glass, and their limits.

Read the guide