What happens if blood is collected without an additive is centrifuged?

When blood is collected without an additive and then centrifuged, it will separate into distinct components due to the centrifugal force. The heavier elements, such as red blood cells, will settle at the bottom, while the lighter components, including serum and any clotting factors, will rise to the top. The resulting layer of serum above the clot can be used for various laboratory tests, but the absence of an additive means that the blood will clot, potentially complicating some analyses.