Cremation involves the incineration of a body after death. The furnace used will generate heat up to 1600-2,000 degrees. It usually takes 2-3 hours depending on the size and weight of the body. Once this is done, all that is left are large bones. These are pulverized to create the ashes that are given to loved ones. Many choose to keep ashes in an urn. Others will spread the ashes over a special place.