Pyrex Lab Glassware: What the Name Means and How to Specify It
Many buyers ask for "Pyrex lab glassware" when they mean clear, heat-resistant glass that can go on a hot plate. The name has become shorthand for a material: borosilicate glass. This guide explains where the name comes from, what the material does, and how to write a spec that gets you the right glass from any bidder.
One point first. Pyrex is a registered trademark, first used by Corning Glass Works in 1915. LabExports does not make Pyrex-branded products. It makes and exports borosilicate lab glassware from India and can quote against a borosilicate 3.3 spec.
Why buyers say Pyrex lab glassware
Pyrex was one of the first widely sold borosilicate glass brands. For decades, lab staff met it in teaching labs and textbooks. Over time, "Pyrex lab glassware" came to mean any glass that survives heating without cracking.
That habit causes problems in buying. A tender that names a brand may exclude equal products. A buyer who writes "Pyrex" may also get kitchenware-grade glass that was never designed for lab work. Naming the material, not the brand, avoids both issues.
Borosilicate 3.3: the material behind the name
Borosilicate glass 3.3 is defined in ISO 3585. It is mostly silica, with about 13% boron oxide. The "3.3" is its thermal expansion, about 3.3 × 10⁻⁶ per kelvin. That is roughly a third of ordinary soda-lime glass.
Low expansion is what makes it useful. When one side of the glass heats faster than the other, it barely changes size, so stress stays low. This gives three practical benefits:
- Thermal shock resistance: it copes with heating and cooling far better than soda-lime glass.
- Chemical resistance: it resists water, most acids and most organic solvents. Hydrofluoric acid, hot phosphoric acid and strong hot alkalis still attack it.
- Clarity: it is clear and colourless, so you can watch reactions and colour changes.
Makers often quote a maximum working temperature near 500 °C. That figure applies for short periods, to items free of stress, and without sudden temperature change. Always check the maker's data sheet, and never heat thick-walled or volumetric items that far.
Borosilicate 3.3 vs soda-lime glass
| Point | Borosilicate 3.3 | Soda-lime glass |
|---|---|---|
| Thermal expansion | About 3.3 × 10⁻⁶ K⁻¹ | About three times higher |
| Direct heating | Suitable | Prone to cracking |
| Chemical resistance | High for most reagents | Lower; can leach alkali |
| Typical lab uses | Beakers, flasks, condensers, burettes | Some bottles, slides, simple storage |
| Cost | Higher | Lower |
Not all glass sold as Pyrex is lab grade
The Pyrex name also appears on kitchenware. In some markets, that kitchenware is made of tempered soda-lime glass, not borosilicate. It may look the same, but it is not made for lab heating, lab chemicals, or volumetric accuracy. For lab work, ask for the glass type on the data sheet, whatever the brand.
How to specify borosilicate instead of a brand
Many public buying rules discourage brand names in specs, or ask for "or equivalent" wording. A clear material spec does the same job and keeps bids comparable. Include:
- Glass: borosilicate glass 3.3 conforming to ISO 3585. US-style specs may cite ASTM E438, Type I, Class A.
- Item standard: for example ISO 3819 for beakers or ISO 1042 for volumetric flasks.
- Accuracy class: Class A or Class B for volumetric items.
- Size and marks: capacity, graduations, and printed or etched marks.
- Joints and stopcocks: ground-glass joint size and glass or PTFE stopcocks.
- Marking: glass type and capacity shown on each piece.
Common borosilicate items to request
These are the items buyers most often mean by the name. The catalog lists many of them:
- Beakers, including conical beakers.
- Flasks: conical, flat-bottom, round-bottom, three-neck, distillation, filter and volumetric.
- Burettes with glass or PTFE stopcocks.
- Condensers, stillheads, adapters and ground-glass joints.
- Reagent, dropping, wash and gas washing bottles.
- Centrifuge tubes and desiccators.
Care and safe use
Borosilicate is tough, but it is still glass. Check each piece for chips, cracks and scratches before heating. Heat gradually, and use a wire gauze or a heating mantle rather than a bare flame where you can. Do not set hot glass on a cold, wet surface. Your safety officer and the maker's manual should set local rules.
Requesting a quote
Send an item list with glass type, sizes, accuracy class and quantities, plus the delivery country. If the order is for a tender, include the reference and required documents. LabExports can prepare spec sheets and quotations for government and institutional tenders. For wider buying advice, see the tips for buying high-quality laboratory glassware, then request a quote.