Cremations are performed in a special unit called a retort or cremation chamber. The cremation chamber consists of two firebrick lined spaces, usually situated on top of the other. The primary space is for cremation of the body and container encasing the body. Gases including particulates, ("smoke" in laymen’s terms), pass into the secondary space of the cremation chamber. Those gases go through intense burner flames and heat in order to burn the particulate matter. Ideally, only heat waves are visible as the gases exit the cremation chamber into the air.
The cremation chamber is designed by manufacturers to handle temperatures up to approximately two thousand degrees Fahrenheit. State and province temperature set points are below that level and differ among jurisdictions. Cremation chambers start the cremation by bringing the temperature of the smoke burning space up to a certain set point, somewhere around sixteen hundred degrees Fahrenheit in most jurisdictions. That achieves particulate or smoke burning capability when the actual cremation starts in the primary space containing the body.
The actual cremation takes one to three hours depending on the efficiency of the cremation chamber and size of the body. An additional time period of up to an hour allows cooling before the cremated remains are raked and swept from the cremation chamber. The cremated remains are in the form of pieces ranging from fine dust to shards several inches long. Metals and other non-combustible foreign materials are removed by magnet.
Other non-magnetic items are removed by visual inspection. The various foreign items come from implants in the body, casket or container materials and clothing items such as buttons, buckles, snaps, zippers, brads and rivets. Cremated remains or ashes are placed in a pulverizing machine manufactured specifically for the purpose of reducing cremated remains to a powdered consistency. This is a short step of only a minute or two in the most efficient pulverizing machines.
The cremated remains are placed in either a temporary container or the permanent urn if it has been selected. A heavy duty vinyl bag is used as the inner liner when possible to guard against accidental spills due to breakage or rupture of the outer container or urn. In situations where families specify biodegradable urns for burial in memory gardens at churches or at sea, the vinyl bag is not used. Name labels are placed on vinyl bags and the outer container or urn. Metal discs are used in some jurisdictions through the entire process to identify the cremated remains in each step. The crematory operator is finished and transfers custody of the cremated remains to another person for the After Cremation steps.