They had broken into a Chinese cave to discover one of the finest collections of documents and paintings from the heyday of the Silk Road, a trading route which stretched across Central Asia, all perfectly preserved by the desert climate.

Now a Yorkshire company has is helping experts ensure that the parchments will survive for another 1,000 years. The conservationists are using paper dyes from Leeds-based chemicals company Clariant UK.

The hand-written manuscripts, now housed at the British Library in London, were brought to the UK by Hungarian-born explorer and archaeologist Sir Marc Aurel Stein, after being discovered in a library cave in 1907 in north-west China.

They provide a glimpse of life in China at the turn of the first millennium.

For centuries, Buddhist monks and their followers made scores of cave temples out of the cliffs outside Dunhuang – an oasis town at the fork of the northern and southern trade routes of the Silk Road.

Mark Barnard, Chief Conservator at the British Library, said: "The manuscripts are in a relatively fragile state and one of our key tasks is to strengthen them and prevent deterioration.

"One way of doing this is to 'bond' any frayed edges with fresh paper so that they have clean and complete edges.

"This technique stops the paper from tearing and enables the manuscripts to be safely stored as scrolls, which conserves their original colour and calligraphic style, or brushmanship.

"Before bonding the manuscript edges with new paper, we want to ensure that the colour matches so as not to ruin their appearance. This is where Clariant dyes come in."
Clariant's cartasol dyes are used to dye Japanese tissue paper which is pasted on to the original manuscript.

The paper is dyed using a 'float dye' technique where the paper is floated on water mixed with the Clariant cartasol dyes.

Once dry, it is then water-cut, or torn, and the frayed edges of the paper are joined to the edges of the manuscript.

Mike Wylie, Product Manager for Paper Dyes at Clariant, said: "We are delighted our products are helping to play a part in the conservation of these historic manuscripts."

Clariant UK employs 350 staff in Leeds, and is part of the global Clariant Group which has 100 companies on five continents and employs 23,000 people. The headquarters are in Muttenz, near Basel, Switzerland.