Modern cremation process.
The cremation occurs in a crematory (or crematorium), consisting of one or more cremator furnaces or ccremation retorts for the ashes. A cremator is an industrial furnace capable of generating temperatures of 870-980 °C (1,598-1,796 °F) to ensure the disintegration of the corpse. A crematorium may be part of chapel or a funeral home, or part of an independent facility or a service offered by a .
Modern cremator fuels include natural gas and propane. However, coal and coke were used until the early 1960s.
Modern cremators have adjustable control systems that monitor the furnace during cremation. These systems automatically monitor the interior to tell when the cremation process is complete, after which the furnace shuts down automatically. The time required for cremation thus varies from body to body, and in modern furnaces may be as fast as one hour per 45 kilograms (99 lb) of body weight.
A cremation furnace is not designed to cremate more than one body at a time, something that is illegal in many countries, including the U.S. Exceptions are sometimes made in extreme cases, such as of a deceased mother and her still-born child or still-born twins, but in these cases the mother and child must be placed in the same cremation container.
The chamber where the body is placed is called the retort and is lined with heat-resistant refractory bricks. The coffin or container is inserted (charged) into the retort as quickly as possible to avoid heat loss through the top-opening door. The container may be mounted on a charger (motorised trolley) that can quickly insert the container or on a fixed or movable hopper that allows the container to slide into the cremator.
Modern cremators are computer-controlled to ensure legal and safe use. For example, the retort door cannot be opened until the cremator has reached its operating temperature, and United States federal regulationsrequire that newly constructed cremators feature dual electrical and mechanical heat shutoff switches and door releases accessible from inside the retort. Refractory bricks are typically replaced every five years because thermal fatigue gradually introduces fissures reducing their insulating strength.
Some crematoria allow relatives to view the charging. This is sometimes done for religious reasons, such as in traditional Hindu and Jain funerals.
Most cremators are a standard size. Typically, larger cities have access to an oversize cremator that can handle deceased in the 200 kilograms (440 lb)+ range. Most large crematoria have a small cremator installed for the cremation of foetal and infant remains.
The cremation
The coffin containing the body is placed in the retort and incinerated at a temperature of 760° to 1150°C (1400° to 2100°F). During the cremation process, a large part of the body (especially the organs) and other soft tissue are and oxidised by the intense heat; gases released are discharged through the exhaust system. The process usually takes 90 minutes to two hours, with larger bodies taking longer time.
What remains after cremation are dry bone fragments. Their colour is usually light grey.
Jewellery, such as wristwatches and rings, is ordinarily removed before cremation, and returned to the family. The only non-natural item required to be removed is a pacemaker, because it could explode and damage the cremator; the mercury contained in a pacemaker's batteries also poses an unacceptable risk of air pollution. In the United Kingdom, and possibly other countries, the undertaker is required to remove pacemakers prior to delivering the body to the crematorium, and sign a declaration stating that any pacemaker has been removed.
The grinding process typically takes about 20 minutes.
The ashes are then placed in a container. The default container used by most crematoriums, when nothing more expensive has been selected, is almost always a hinged snap-locking box of plastic.
Ash weight and composition
Cremated remains are mostly dry calcium phosphates with some minor minerals, such as salts of sodium and potassium. Sulphur and most carbon is driven off as oxidised gases during the process, although a relatively small amount of carbon as carbonate may remain.
The ash remaining represents very roughly 3.5% of the body's original mass (2.5% in children). Because the weight of dry bone fragments is so closely connected to skeletal mass, their weight varies greatly from person to person. Because many changes in body composition (such as fat and muscle loss or gain) do not affect the weight of cremated remains, their weight can be more closely predicted from the person's height and sex than from their simple weight.
Ashes of adults can be said to weigh from 4 pounds (1.8 kg) to 6 pounds (2.7 kg), but the first figure is roughly the figure for women and the second for men. The mean weight of adult cremated remains in a Florida, U.S. sample was 5.3 lb (approx. 2.4 kg) for adults (range 2 to 8 lb or 0.91 to 3.6 kg). This was found to be distributed bi-modally according to sex, with the mean being 6 pounds (2.7 kg) for men (range 4 to 8 lb or 1.8 to 3.6 kg) and 4 pounds (1.8 kg) for women (range 2 to 6 lb or 0.91 to 2.7 kg). In this sample, generally all adult cremated remains over 6 pounds (2.7 kg) were from males, and those under 4 pounds (1.8 kg) were from females.
Cremated remains are returned to the next of kin in a rectangular plastic container, contained within a further cardboard box or velvet sack, or in an urn if the family had already purchased one. An official certificate of cremation prepared under the authority of the crematorium accompanies the remains, and if required by law, the permit for disposition of human remains, which must remain with the cremated remains.
Cremated remains can be kept in a cremation urn, stored in a special memorial building (columbarium), buried in the ground at any location or sprinkled on a special field, mountain, or in the sea. In addition, there are several services in which the cremated remains will be scattered in a variety of ways and locations. Some examples are via a helium balloon, through fireworks, shot from shotgun shells, or scattered from an airplane (this is not illegal in most jurisdictions, in part because laws prohibiting it would be difficult to enforce). One service sends a lipstick-tube sized sample of the cremated remains into low earth orbit, where they remain for years (but not permanently) before re-entering the atmosphere. Another company claims to turn part of the cremated remains into synthetic diamonds that can then be made into jewellery. Cremated remains may also be incorporated, with urn and cement, into part of an artificial reef, or they can also be mixed into paint and made into a portrait of the deceased. They can also be scattered on private property with the owner's permission. A portion of the cremated remains may be retained in a specially designed locket known as cremation jewellery. The cremated remains may also be entombed. Most cemeteries will grant permission for burial of cremated remains in occupied cemetery plots that have already been purchased or are in use by the families disposing of the cremated remains without any additional charge or oversight.
The above information has been sourced from Wikipedia http://en.wikipedia.org/wiki/Cremation
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