What really happens during cremation?

City of London Crematorium with flowers on grass outside

Six minute read

There are lots of misconceptions about what happens during cremation. That’s no surprise — talking in detail about cremation can sometimes feel like breaking a taboo. But hiding what really happens can lead to unnecessary confusion and fear.

We’ll walk you through the process of cremation, from gathering ashes to where our knee replacements get recycled, and bust a few common myths about cremation on the way.

What exactly happens during cremation?

Crematoria are set up for holding funerals, which means that there’s a room specifically for the ceremony. In the ceremony room, the coffin is put on a rectangular platform called a catafalque. You can decide what happens to the coffin when the ceremony ends. Lots of people choose to have the coffin stay on the catafalque while the people at the funeral say their goodbyes and leave.

Eventually, the coffin is 'committed' which means it goes through doors or is lowered through the catafalque to the cremation room. The cremator isn’t directly behind the doors or curtains — so, if you want to watch the coffin leave, you won’t see any flames.

But the committal can happen later — it doesn't have to be witnessed by those at the service. After the committal, the coffin is brought somewhere cool until the cremation itself.

Lots of people have specific questions about things like the heat of the cremator — which varies but is generally around 900 °C; or the time it takes to cremate someone — which depends on things like body size and composition.

There’s nothing strange about wondering what might happen and you should always feel free to ask your funeral director any questions.

You do not have to use your local crematorium — this guide takes you through how to choose a crematorium and what questions to ask.

What is the 'charging'?

The ‘charging’ is when the coffin, with the person who has died inside, is put into the cremator. While this won’t be right for everyone, some people find that witnessing the charging can be a powerful part of saying goodbye. At some crematoria, you can witness the charging if you book a special slot ahead of time.

How are ashes collected?

Once the cremation is finished, it takes about an hour for the ashes to cool down enough for a technician to collect. There is usually bone left behind which goes into the cremulator — a kind of specialised machine to turn bone into ash.

At this point, the ashes are gathered for family and friends to pick up. If you’d rather not collect ashes, they can be scattered at the crematorium instead, usually in a garden or other area set aside specifically for this. Read more about your options for keeping or scattering ashes.

Does cremation happen right after the ceremony?

A person might be cremated right after the ceremony but it depends on how busy the crematorium is. The reason why cremation doesn’t always happen immediately is to make it better for the environment.

It takes some time for the cremator to get hot enough, which means it isn’t very energy efficient to only have one cremation per day. Technicians will usually organise cremations so they happen one after the other and the heat isn’t wasted. It would be very unusual for them to wait for more than three days — and most cremations will happen sooner than that.

Some families and friends feel it’s important to have someone cremated immediately for personal or religious reasons. If that’s the case, a funeral director can help you make the right booking with the crematorium. If you ask to witness the charging of the coffin, it will always take place right after the ceremony.

Do they reuse the coffin?

One common myth is that people are taken out of their coffin before cremation so it can be reused. But someone’s coffin will absolutely not be taken away from them.

The person who has died will stay inside their coffin as they go into the cremator, along with anything else that’s been included — like photos, flowers, and letters.

Could I be cremated with someone else?

Another really common myth is that multiple people are cremated at once. As a result, family and friends sometimes worry that the ashes they get back might come from more than one person. It’s an understandable concern to have, but this is absolutely not the case.

The Code of Cremation Practice says the person who has died must be cremated on their own. All the ashes are collected before the cremator is used again and so will definitely belong to your person and nobody else.

Watch this short 'Ask A Funeral Director' video which explains how you can be sure you are collecting the right ashes

What items can't go inside a cremator?

Not just anything can go inside a cremator. There’s no single list of items that can’t be included but it’s a good idea to remove anything with liquid that might explode and damage the cremator. Heavy plastics, glass, and anything with batteries (like watches) should be left out too.

Our lovely local cremator technician told us that bottles of alcohol and perfume are items which should definitely not be put in a coffin.

Your funeral director can talk you through what may or may not be a good idea to include. They can also help find ways to help involve special items in the funeral ceremony even if they can’t go inside the coffin.

What happens to joint replacements?

The crematory technician will go through the ashes and remove any metals before they go in the cremulator. These metals are normally things like hip and knee replacements, as well as bits of wire from the coffin.

Right now, all of the UK’s crematoria metal waste gets recycled by a single company in the Netherlands. You can also ask for the joints back if you’d like to.

Is cremation bad for the environment?

Unfortunately, cremation isn’t great for the environment, because it uses a lot of energy and can release chemicals into the air. The good news is that crematory technology has moved ahead by leaps and bounds over the past decade.

There are new rules about reducing emissions, and the technology is better at filtering out chemicals like mercury so they don’t end up in the atmosphere. There are also lots of other ways you can help make your funeral more eco-friendly if this is important to you.