When we talk about the terracotta army, most of us probably picture the legions of lifelike stone soldiers. But when they were first discovered, they were broken into thousands of pieces. So how were they restored to their former glory?

The magnificent sight of the Terracotta Warriors has drawn countless tourists to the ancient city of Xi’an. But they didn’t look like this when they were first unearthed. The restoration was a complicated and painstaking process, that required the steady hands of veteran archaeologists.

First, the fragments have to be thoroughly cleaned before even attempting to put them back together.

Lan Desheng, from restoration centre of Museum of Qin Shihuang Imperial Mausoleum says, "We do the work very slowly. While cleaning them, we use bamboo picks in order not the damage the colourful paintings on the relics and also to avoid the scraping the surface. It is extremely difficult when it comes to ones that feature leather or colour paintings on the surface, because it’s very easily damaged or contaminated. For coloured ceramic relics, there are 19 kinds of contamination which can erode the ceramics on the relics here we’ve found 18 of them. If the contamination isn’t cleaned up thoroughly, the relics will be further eroded in the future.

The cleaning process is just the first step. Assembling the thousands of fragments is even more complicated. It’s vital to keep track of all the valuable historical information that might be revealed by the fragments, so workers have to number and analyse each and every one of them. In order to keep accurate records, a good system is key.

Lan Desheng says, "For very damaged piece, we give them big numbers, and for comparatively complete pieces, we give them a small number.

For example, this piece of terracotta, the name for it is T23G924, number is 36."

Based on the analysis of all the fragments, archaeologists can figure out which fragment belongs to which statue. Then it’s time to begin reconstructing the statues from the shattered pieces.

What a wonderful job if you love 3D jigsaws.

Lan says, "Firstly, we try to patch up the fragments of the main statues and see which pieces fit. We begin from the pedestals, and then the feet, the ends of gowns, then the body, then the head. That means going from bottom to top. The secrets lies in finding the right places to make the connection. If you do that right everything will start falling into place. "

It can take a lot of unsuccessful attempts before finding the right combination. Once the right connection is found, work can begin on grafting them to the main body. All these warriors and horses are life-sized, so it is impossible to put them all together at once. The experts have to start from the smallest body parts and work their way up to the biggest.

Lan says, "The bonding process is the most important job. If the bonding goes well, the terracotta will be nice and firm. Otherwise, some of them collapse again within a few years. We use dual epoxy resin, layer by layer, to bond them. It takes 24 hours to harden."

Normally, for a badly damaged statue, it takes 3 to 5 months to complete the restoration. So far, archaeological workers in this centre have already restored more then 1,000 statues. Thanks to their hard work, the great army of the Qin emperor might one day be completely restored to its former glory.