Centrifuge Tubes

Pick the size closest to your working volume. A tube that is barely filled wastes rotor space and a tube filled to the brim risks spilling under spin, so aim to fill somewhere around three quarters.

Polypropylene is unbreakable and fine for most aqueous work. Borosilicate glass is the better choice where solvents would attack plastic or where you need to see the sample with real clarity.

Sterile tubes come individually wrapped and ready to use, which matters for microbiology and cell work. For general chemistry and school practicals, non sterile tubes in bulk cost noticeably less.

A pointed conical tube needs a rack to stay upright. Free standing tubes have a moulded skirt at the base, which is worth having if bench space is tight or you are working without a rack.

It holds a sample while a centrifuge spins it at speed. The spin drives denser material down to the conical tip as a pellet, leaving the lighter liquid above it, which is how you separate solids from a liquid or one liquid layer from another.

A centrifuge tube has thicker walls to survive the force of spinning and usually a conical bottom to gather the pellet. A test tube has a round bottom, thinner walls and is meant for heating, mixing and observing rather than spinning.

Polypropylene tubes are generally autoclave safe, but always check the temperature rating on the specific product first. Glass tubes autoclave without trouble. Never autoclave a tube with the cap screwed down tight, since pressure needs somewhere to go.

Yes, always. Place tubes of equal weight opposite each other in the rotor. An unbalanced load makes the machine vibrate badly, can crack tubes and will damage the centrifuge over time. Use a water filled tube to balance an odd sample.

Glass tubes and heavier polypropylene tubes wash and reuse well for general work. Sterile single use tubes should be discarded after one use, since washing breaks the sterility they were sold for and can scratch the wall.