Cremation is a process of thermal reduction, using intense heat to reduce a body to its basic elements. The resulting material, often mistakenly called “ash,” is actually composed of processed bone fragments. This substance is primarily mineral matter, which survives the high temperatures of the cremation chamber. Only one biological component of the body consistently remains after the process.
The Cremation Process and Heat Effects
The body is placed in a specialized chamber, known as a retort, which operates at extremely high temperatures. Modern cremation typically uses temperatures between 1,400 and 1,800 degrees Fahrenheit (760 to 980 degrees Celsius). This intense thermal environment ensures the complete reduction of organic matter.
Soft tissues, such as muscle, fat, and internal organs, are completely destroyed. They are vaporized and oxidized by the heat and forced air within the chamber. This process converts the soft tissue into gases, primarily carbon dioxide and water vapor, which are safely vented. Only a trace amount of true carbon ash remains.
What Biologically Remains?
The skeletal structure is the only biological material that consistently withstands the heat. While soft tissues are consumed, the dense mineral matrix of bone does not burn away completely. Bone does not combust because its composition is only about 30% organic material.
The primary process affecting the bone is calcination, not burning. Calcination is a chemical change where organic components, such as collagen, are destroyed and driven off as gases. This high-temperature exposure leaves behind a brittle, porous mineral structure.
The remaining material is almost entirely calcium phosphate, the inorganic mineral that provides bone structure. This mineral is a form of hydroxyapatite, which is highly resistant to heat. The result is a collection of white or gray bone fragments that are extremely fragile. These fragments are then processed into the fine, granular material commonly called “cremains.”
Identifying and Separating Non-Biological Materials
Beyond the skeletal remnants, non-biological foreign objects present in or on the body can survive the process. Large surgical implants, such as titanium hip replacements or steel rods, often survive intact. Their melting points are far higher than the chamber’s operating temperature.
Smaller items, like dental fillings containing gold or silver alloys, may melt but remain as small metallic remnants. These metallic objects must be separated before the final processing of the bone fragments. Separation is often accomplished using a powerful magnet or by hand-sorting the cooled remains.
Certain medical devices, like pacemakers, must be removed before the process begins. Their batteries or components could explode under the intense heat, potentially damaging the retort. The material returned to the family consists purely of the processed bone mineral, free from metallic or synthetic foreign objects.