The common term “ashes” is used to describe the material remaining after a cremation, but this description is not chemically accurate. Cremation is a process of thermal reduction that uses intense heat to reduce a body to its basic chemical elements. The final material returned to the family is not soft, flaky ash, but the durable mineral components of the skeletal structure. This material is often referred to as “cremated remains” or “cremains,” representing the body’s most resistant matter after organic tissues have been vaporized.
The Reduction Process
The body is placed in a combustible container and introduced into a cremation chamber, a specialized furnace called a retort. The chamber is heated to temperatures ranging between 1,400 and 1,800 degrees Fahrenheit (760 to 982 degrees Celsius). This heat quickly ignites the container, causing the body’s soft tissues and moisture to be consumed or vaporized into gasses.
The entire process typically takes two to three hours for an average adult, varying based on body mass and bone density. The thermal exposure ensures that all organic matter is broken down into its elemental forms. What remains within the chamber after this stage is a collection of dried, brittle bone fragments.
The True Nature of Cremated Remains
The material that survives the high temperatures is primarily the inorganic component of human bone. This substance consists of mineralized bone fragments, not ash in the traditional sense. The remains are mostly composed of calcium phosphate, the hard, mineral basis of the skeleton.
Bone is naturally resistant to heat because its structure, called hydroxyapatite, does not readily break down during standard cremation temperatures. While organic material like collagen is destroyed, the calcium phosphate framework remains intact. Trace elements like sodium, potassium, and magnesium, naturally incorporated during life, may also be present.
Separation of Non-Organic Materials
The thermal reduction process is effective against organic matter, but certain non-biological materials resist breakdown and survive the heat. Metallic implants, such as hip or knee replacements, surgical pins, and screws, are made of durable alloys and remain in the chamber. These items, along with any metal components from the cremation container, must be separated from the human remains.
Once the bone fragments have cooled, crematory operators collect them and use strong magnets to remove ferrous metal objects. Non-magnetic metals, such as certain dental fillings or gold, are manually sorted and removed. These separated metals are typically gathered for recycling, a common industry practice.
Final Appearance and Quantity
The material removed from the chamber consists of coarse, un-uniform bone fragments, not the fine powder families expect. To achieve a uniform appearance, these fragments are placed into a specialized machine called a cremulator. The cremulator uses a mechanical process to reduce the pieces into a consistent, granular texture, similar to coarse sand or fine gravel.
The final cremated remains, or “cremains,” typically range in color from off-white to light gray. The quantity varies depending on the person’s height and bone density, but adult remains generally weigh between 3 and 9 pounds. This volume is usually sufficient to fill a standard urn.