The study of physics and chemistry is confusing.... So when the local crematorium says your aunt's gold dental fillings can't be recovered, what should you think? And what about her old silver fillings, what happens to the mercury in them?
The standard crematorium kiln operates at between 800 - 1000 degrees Celsius.
The average gold filling contains about 75% gold with the other main ingredients being palladium and silver. (There are a few other less common ingredients such as Platinum, Copper and Zinc.)
Gold dental alloys melt at an average 930 degrees celsius and silver at 961 degrees. This suggests the dental fillings may turn to either liquid gold or globules. So what happens to this gold? And where does the mercury go?
The Smoke-Buster Ener-Tek IV Cremation System (The "Utimate in Production and Performance")
Cremation takes about 90 minutes. (Though the latest cremation systems can turnover as many as 15 bodies in 18 hours.)
After incineration the bone fragments are swept out into a retort.
A magnet is run over the cooling remains to pick up any metal objects such as surgical pins, articial limbs and coffin nails. (Stainless steel, chrome, iron and a few other metals do not melt in the furnace. These metals melt at much higher levels than gold and silver.)
The use of the magnet might not detect gold and silver, as they are not very magnetic. However staff also do a manual sort of the remains.
If the gold and silver have liquified they should have cooled during this process. They might now be identifiable as molten fragments. Gold boils at about 2,800 degrees celsius (silver about 2,200 degrees celsius), so it cannot vaporise during the cremation process. Nevertheless according to crematoria operators, no gold fragments are found.
At the end of sorting, the bone particles are placed into a cremulator by the operator, where they are pulverised.
The mercury in the meantime has been released into the atmosphere. In the UK, mercury from crematoria is expected to cause 35 percent of mercury emissions by 2020.
There is debate over how much, if any, mercury in the air is acceptable. US research indicates that the cremation of one human lets off 2.0 to 3.0 grams of mercury into the atmosphere.
To reduce this, the US State of Minnesota has proposed legislation requiring that all mercury dental fillings be removed before cremation. The legislation requires a mortician or a supervised technician remove teeth containing fillings. This prevents the mercury being released as vapour.
Mercury emissions can be reduced by the use of charcoal filters or by adding a capsule of selenium to the coffin. The selenium transforms the mercury into the less harmful (but still polluting) mercury selenide. This is deposited onto the chamber walls of the crematorium.
Funeral industry operators say metal parts are normally discarded after cremation because these parts are unrecognizable or hazardous. In the US they may be sent to landfills.
According to Invocare (Australia's biggest funeral industry business) metallic contents are buried:
"When cooled, metallic contents (such as prostheses, coffin nails etc) are removed, collected and interred within the grounds of the crematorium."
Invocare makes no mention of the gold dental fillings. Perhaps it is included within their "etc".
Whatever, it would seem the impression given to many relatives by some in the funeral business is that their loved one's metal bits are either safely buried or have just vanished; and have not been sold off to scrap and precious metals recyclers.
Relatives interested in visiting these remains, should perhaps ask crematorium staff where the metal is interred. Given the amount of metal hips, artificial joints and dental fillings passing through a crematorium it should be well known to staff.
http:www.alphadent.co.kr/eng/product/product.htm
http://www.bgop.org/melting_points.pdf
http://www.matthewscremation.com/
http://www.medcure.org/forms/cremation_auth.pdf
http://www.dentalmumbai.com/fillings.htm (Gold dental fillings picture)
Matthews Cremation Division, Apopka, FL, US (pictures of the Elder Davis cloth-covered cardboard casket and the Ener-Tek IV Cremation System)
