Culture Tubes for Microbiology: Glass vs Disposable Plastic
Culture tubes come down to one decision: reusable borosilicate glass or single-use plastic. Glass wins where you autoclave repeatedly, work at high temperature, or handle solvents. Plastic wins where you need sterility out of the bag, unbreakable handling, or high throughput without a wash-up burden.
Below: how the three materials differ, why polystyrene and polypropylene are not interchangeable, and how to match cap size to tube diameter so your closures actually seal.
Glass vs plastic: the core tradeoff
Borosilicate glass
Type I borosilicate is the standard for reusable microbiology. It has a low coefficient of thermal expansion, so it survives repeated autoclave cycles and direct flame without stress cracking, and it is chemically inert against solvents and strong acids that would craze or dissolve plastic. It is also optically clear and stays that way — no clouding after cleaning.
The costs are breakage and labor. Every reuse cycle means washing, drying, re-capping, and re-sterilizing, and that labor is usually the larger expense over a year than the tubes themselves.
Polystyrene (PS)
PS is rigid and the most optically clear of the plastics, which makes it the default for anything read on an instrument — turbidity, absorbance, flow cytometry sample tubes. It is not autoclavable and it is attacked by many organic solvents, including alcohols in concentration, acetone, and aromatic hydrocarbons. Treat PS as strictly single-use.
Polypropylene (PP)
PP trades clarity for chemical and thermal resistance. It is autoclavable, tolerates a far wider solvent range than PS, and survives freezing without cracking, which matters if tubes go from culture to storage. It is translucent rather than water-clear, so it is a poor choice for optical reads.
Comparison at a glance
| Property | Borosilicate glass | Polystyrene | Polypropylene |
|---|---|---|---|
| Autoclavable | Yes | No | Yes |
| Optical clarity | Excellent | Excellent | Translucent |
| Solvent resistance | Excellent | Poor | Good |
| Breakage risk | High | Low | Very low |
| Freezing | Risky | Brittle | Good |
| Typical use | Reusable culture | Optical reads | Culture to storage |
Sterile vs non-sterile
Sterile plastic tubes are irradiated and bagged ready to use. Non-sterile costs less per tube and is the right call when the tube will be autoclaved with media anyway, or when the work is not aseptic. Buying sterile and then autoclaving it is paying twice for the same outcome.
For work involving infectious or potentially infectious material, containment practice is set by the CDC and NIH Biosafety in Microbiological and Biomedical Laboratories (BMBL) manual, which governs the biosafety level and the handling your tube choice has to support.
Where tubes are reprocessed rather than discarded, the CDC's Guideline for Disinfection and Sterilization sets out the steam sterilization parameters your glass and PP tubes need to withstand.
Standardizing a tube format? Browse the full culture tubes collection to compare glass and plastic in matching diameters before you commit a protocol to one format.
Sizing: diameter drives everything
Culture tubes are specified as diameter × length in millimetres, and diameter is the number that matters — it determines rack fit, cap fit, and centrifuge adapter fit. Common formats:
- 10 × 75 mm (4 mL) and 12 × 75 mm (5–6 mL) — small-volume work, flow cytometry, the classic "5 mL tube". Available in borosilicate, sterile PS and sterile PP
- 13 × 100 mm (10 mL) and 16 × 100 mm (14 mL) — routine broth culture
- 16 × 125/150 mm (19–23 mL) — larger broth volumes, glass most common
- 17 × 100 mm (15 mL) — sterile PP and sterile PS
- 18–20 × 150 mm (29–36 mL) — large-volume glass
Caps have to match the tube, not the rack
Polypropylene closure caps are sized to tube outside diameter, and a cap one millimetre off will either not seat or will fall off in the incubator. We stock diamond-style PP caps in 13 mm, 16 mm, 18 mm, 20 mm and 25 mm. These caps are vented-style closures for aerobic culture — if you need a gas-tight seal for anaerobic work, that is a different closure class.
Related guides
- Lab Tubes & Vials: The Definitive Selection Guide — the pillar guide this post sits under
- Test Tube Materials Guide: Glass, Plastic & Specialty Options
- How to Set Up a Cell Culture Workspace
- Tube Racks: Universal, Floating & Stackable Options
- Borosilicate vs Soda-Lime Glass: Which Does Your Lab Need?
Frequently asked questions
Can polystyrene culture tubes be autoclaved?
No. Polystyrene deforms well below steam sterilization temperature. Use polypropylene or borosilicate glass if the tube must be autoclaved.
Why choose polystyrene over polypropylene?
Optical clarity. PS is water-clear, so it is the better choice for turbidity readings, absorbance, and flow cytometry. PP is translucent and scatters light.
Are glass culture tubes cheaper than plastic?
Per tube, no — but glass is reusable across many autoclave cycles. The real comparison is glass plus wash-up labor against the running cost of single-use plastic at your throughput.
What size cap do I need?
Match the cap to the tube outside diameter in millimetres, not the volume. A 16 × 100 mm tube takes a 16 mm cap.
Do I need sterile tubes?
Only if the tube goes into aseptic work as-is. If it will be autoclaved with media anyway, non-sterile is the cost-effective choice.
Spec your tubes with us
Tell us your diameter, volume, and whether the tube is being autoclaved or read on an instrument, and we will match the format. Shop culture tubes and closures.
By the LabSupplies.com Technical Team