There are many ways of harvesting the fat and processing the fat after a Brazilian butt lift. Purifying the fat is a very broad term. When harvesting the fat with liposuction, there are many products that will be suctioned with fat that need to be removed prior to fat injection. A fluid called tumescence is injected in the areas to be suctioned. This fluid contains lidocaine (numbing medicine) and Epinephrine (medication to control bleeding). When the fat is harvested, the fluid is a combination of fat, lidocaine, epinephrine and blood. Ideally, only the fat is injected in the buttocks. This is the reason why removing any but the fat that was harvested is important. There is a debate on which is the best option. Some surgeons advocate centrifuging the fat (spinning the fat); others rinsing the fat with saline, etc. I typically do minimal manipulation of the fat to remove the blood and all the unnecessary products. This has been shown in experiments to be the best way to improve fat survival.