A glossary of labware terms

Labware arguments are usually vocabulary arguments. Two people say flask and mean different volume claims. This glossary defines the words that change a method, and compares the pairs that get substituted for each other. The narrative map of which vessel to pick is choosing laboratory glassware. Plastic formats sit beside that map in when to use plastic tubes, tips and plates.

Borosilicate 3.3 and soda-lime

Borosilicate 3.3 is a low-expansion laboratory glass. The 3.3 recalls a linear expansion near 3.3 millionths per kelvin, which is why intact ware of this type tolerates hot plates and autoclaves better than ordinary bottle glass. Soda-lime expands more. It is cheaper and more sensitive to thermal shock. ASTM E438 is a public specification that separates a low-expansion borosilicate, an alumino-borosilicate, and a soda-lime type. Trade names identify a manufacturer's line. They do not replace the glass-type words. Compare two beakers by the printed glass, not by how blue the catalogue photo is.

To contain and to deliver

To contain, often printed In or TC, means the mark states the volume held inside. A film left behind when you pour is not part of a delivered volume. Volumetric flasks are normally to contain. To deliver, often Ex or TD, means the mark states what leaves the vessel under a stated drain. Many volumetric pipettes and some cylinders are to deliver. Comparing an In flask with an Ex pipette as if both "are 10 millilitres" ignores the film. Blow-out marks are a further delivery convention. If the pipette does not say to blow out, that last drop is not in the calibration.

Class A and Class B

On volumetric glass, Class A is the tighter tolerance class in the applicable standard, and Class B is the wider class. Both are real claims. A beaker graduation is not in this pair at all. The numerical tolerance belongs on the certificate and in the standard. NIST's Office of Weights and Measures is the public doorway into that metrology. Compare Class A with Class B when you are buying flasks. Do not compare Class A with "looks accurate". A Class B flask used and recorded as Class B is more honest than a Class A flask read warm, tilted, or with a detergent film.

Reference temperature

The volume is defined at the temperature printed on the ware, commonly 20 °C, sometimes 27 °C. Comparing a reading taken on a hot flask with a reading taken at the reference temperature compares two different physical volumes. Let the liquid equilibrate. The comparison you want is between batches read the same way, at the marked temperature.

Meniscus

The meniscus is the curved surface of a liquid in a narrow wall. For clear aqueous solutions the readable point is the bottom of the curve, at eye level, with the vessel vertical. Comparing two operators who stood at different heights is a parallax comparison, not a glass comparison. Opaque liquids follow the vessel's own convention.

Joint size and screw thread

A standard-taper joint designation describes a cone, typically with a diameter clue and a length clue, that must match the socket. Grease, a PTFE sleeve, and a clip are sealing and retention choices on that cone. They are not the size. A GL45 thread is a screw standard common on media bottles. Comparing a 24/29 joint with a GL45 cap is a category error. One mates glass apparatus. The other mates a cap. Force is how the wrong pair fails.

Resin class

Polypropylene, polyethylene, polystyrene, polycarbonate, PET and PTFE are polymer classes. Comparing them is a chemical and thermal comparison, done with the manufacturer's chart for the actual piece. Polystyrene is clear and solvent-sensitive. Polypropylene is the usual aqueous, often autoclave-marked tube. PTFE is a resistant liner or sleeve, not a guarantee for the whole cap. Glass is the comparison partner when the chart is missing.

Piston pipette and volumetric flask

A piston-operated pipette and its tip take a portion. Their vocabulary and user recommendations are in ISO 8655-1. A volumetric flask prepares one bulk volume. Comparing a pipette check with a flask certificate compares two instruments that should both be right and that do not replace each other. A filter tip adds an aerosol barrier. It is not a volumetric class.

Sterile, clean, nuclease-free, endotoxin-controlled

Sterile means a claim about viable organisms, produced by a stated process. Clean means the absence of residue that would disturb the next use: detergent, protein, metals. Nuclease-free and endotoxin-controlled are narrower analytical claims. An autoclave addresses viable organisms when the cycle is valid and does not wash the vessel. Compare the adjective on the pack with the failure mode of your assay before you pay for a tighter claim or, worse, skip a claim you need.

Single-use and reusable

Single-use labware is intended to leave the method after one exposure, which limits carry-over and leaves a waste stream. Reusable glass is washed and returned, which requires a rinse that actually removes the last method and a willingness to retire chipped or etched pieces. Volumetric pieces can lose their calibration assumption after harsh washing. Compare the two on contamination, on metrology, and on the waste rule your institution already has. This glossary does not supply an environmental tally.

Using the words in a method

Write the term that would change the result if it were swapped. "Flask" swaps too easily. "Class A volumetric flask, to contain, 20 °C, borosilicate" does not. "Tube" swaps too easily. "Sterile filter tip for the pipette model, nucleic-acid step" does not. When a control fails, compare the term you wrote with the object that was actually used. A soda-lime bottle in an autoclave, an Ex reading treated as In, or a clear plate in a luminescence run are glossary errors with experimental consequences.

Safety language is not a labware class

Biosafety level, chemical hazard class and radiation rules are institutional assignments. They are not printed as a resin. The WHO laboratory biosafety manual is background for biological work. A sterile tube does not assign containment. This glossary is research education, not a diagnostic labelling standard.

What to send when the words are the specification

Glass type, class, In or Ex, capacity, reference temperature, joint size or thread, resin if plastic, and any sterile or nuclease or endotoxin claim as separate words. Quantity is a count. The laboratory glassware catalogue, the volumetric glassware catalogue and the laboratory plasticware catalogue split those words across real shelves of products. The quote request is where the sentence goes.