Test tubes, centrifuge tubes and Falcon tubes: differences and when to use each

At first glance, they are all tubes. But a test tube, a centrifuge tube, and a Falcon conical tube are designed for different uses, and confusing them can result in a lost sample, a broken tube inside the centrifuge, or a result that cannot be replicated.

In this guide, we explain how they differ, how to choose the right one, and what mistakes to avoid.

Test tubes: the classic for reactions and heating

They are cylindrical tubes with a round bottom, usually without a stopper or graduation.

• Materials: borosilicate glass, soda-lime glass, or plastic (PS or PP).
• Typical uses: simple chemical reactions, mixtures, direct heating (only borosilicate ones), cultures, and temporary storage of samples.
• Strong point: borosilicate ones can withstand heating and can be washed and reused.
• Limitation: they are not designed for centrifugation unless the manufacturer expressly states otherwise.

If you are unsure between borosilicate glass and soda-lime glass, check out our comparison [Borosilicate glass vs. soda-lime glass].

Centrifuge tubes: designed to withstand centrifugal force

They are designed to withstand the force generated during centrifugation. They usually have thicker walls, a screw cap, and graduation markings.

• Cone or round bottom: the cone concentrates the sediment (pellet) at a point and makes it easier to remove the supernatant. The round bottom is used in some applications and specific rotors.
• Materials: mainly PP (resists chemicals well and can be autoclaved). There are also glass and other plastic options.
• Key point: the manufacturer indicates the maximum relative centrifugal force (RCF) that each tube can withstand. This must always be respected.

Falcon Tubes: the popular name for the conical tubes of 15 and 50 ml

"Falcon" is a trademark that gave its name to this format. Today, it is generically referred to as the conical centrifuge tubes of 15 ml and 50 ml with screw caps, manufactured by various brands.

• Materials: usually PP. There are also PET ones, which are more transparent but have less chemical resistance and are not autoclavable.
• Format: conical bottom, printed graduation, writing area, and airtight screw cap. Some 50 ml bottles have a skirt to stand upright.
• Options: sterile or non-sterile, in bags or in racks.
• Typical uses: cell culture, sample preparation, centrifugation of medium volumes, storage and transport of samples.

For smaller volumes (from 0.5 to 2 ml), microtubes are used, which require specific rotors and centrifuges.

Quick comparison

How to choose the right tube

Ask yourself these questions before buying:

1. Are you going to centrifuge? If so, you need a centrifuge tube that can withstand the RCF of your protocol and that is compatible with the rotor and adapters of your centrifuge.
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2. What volume do you handle? Microtubes for less than 2 ml, 15 ml or 50 ml tubes for medium volumes, and larger capacity centrifuge tubes for large volumes.
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3. Are you going to heat the sample? Only borosilicate glass can withstand direct heating.
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4. What chemicals are you going to use? PP withstands most aqueous reagents well. PS is not suitable for many organic solvents. When in doubt, consult the manufacturer's chemical compatibility chart.
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5. Do you need sterility? For cell culture or microbiology, choose single-use sterile tubes or tubes that can be autoclaved (PP or glass, not PS or PET).
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6. Do you need to see the content clearly? PET and PS are more transparent. PP is translucent.

RPM and RCF: they are not the same

Centrifuges display speed in revolutions per minute (rpm), but what really matters is the relative centrifugal force (RCF or ×g), because it also depends on the rotor radius. The same speed generates different forces in different rotors.

The formula is: RCF = 1.118 × 10⁻⁵ × r × rpm²

where r is the radius of the rotor in centimeters. Therefore, the protocols should indicate the RCF and not just the rpm. Always compare that value with the maximum RCF indicated by the tube manufacturer.

Common mistakes to avoid

• Exceeding the maximum RCF of the tube. It is the most common cause of breakage within the centrifuge.
• Centrifuge without balancing. Opposite tubes must have the same weight.
• Fill the tube to the top. Respect the maximum volume indicated for centrifugation.
• Use PS tubes with organic solvents. They can crack or dissolve.
• Autoclave PS or PET tubes. They deform. Only PP and glass are autoclavable.
• Heat plastic tubes with a flame.
• Reuse single-use sterile tubes in applications that require sterility.

Frequently Asked Questions

Can I centrifuge a regular test tube? Only if the manufacturer indicates that it is suitable and up to what RCF. A conventional test tube is not designed to withstand that force and may break.

What is the difference between a 15 ml tube and a 50 ml tube? Mainly the volume and the adapter needed for the centrifuge. The format and material are usually the same.

Can Falcon tubes be autoclaved? It depends on the material. PP ones usually can, following the manufacturer's instructions. PET ones cannot.

Conical or round bottom? The conical one, if you need to collect a sediment and easily separate the supernatant. The round one, if your protocol or rotor requires it.

Conclusion

Test tubes, centrifuge tubes, and conical tubes are not interchangeable. Before choosing, consider the use (centrifuging, heating, or storing), the volume, the chemicals, and the sterility. And if you are going to centrifuge, always check the maximum RCF of the tube.

Do you need help choosing? Tell us about your application and we will recommend the right tube from our catalog.

[View the laboratory tube catalog]