It is important to properly balance a centrifuge because an unbalanced machine can damage the rotor, cause catastrophic damage to the machine itself, or even injure or kill lab personnel working in the room. Balancing a centrifuge involves spreading the weight of the samples across the entire rotor.
When there is an even number of samples, the centrifuge can be balanced by dividing the total number of tubes in half and placing the two sets into the rotor directly opposite each other to create an equal number of tubes on each side. For example, a collection of eight samples is balanced by placing four in a row on each side.
When there is an odd number of samples, a balance tube containing liquid in the same volume and density as the test samples can be used to create an even number of tubes. Alternately, an odd number of tubes can be arranged using an algorithmic pattern based on the specific number of sample tubes and the number of available slots in the centrifuge rotor. As an example, in a 12-slot rotor, balance can be achieved by placing three sample tubes in a triangular pattern, leaving three empty slots between each filled slot.