Paint expert Patrick Baty explains his work to the BBC Devon website
By Jemima Laing
The riddle of the colour of Brunel's Royal Albert Bridge has finally been solved.
Network Rail has confirmed the colour was originally off-white after paint analyst Patrick Baty set to work to get to the bottom of the mystery.
The bridge which spans the River Tamar between Devon and Cornwall is to be refurbished in a three-year £10m restoration plan.
"It's been a particularly interesting project," said Patrick.
Patrick Baty took samples of paint at night
Patrick's work - which he started in October 2009 - has revealed that the whole of the ironwork of the bridge was painted with two coats of a pale stone colour before it was assembled.
Following assembly, a coat of red-brown was applied before a thick layer of an "anti-corrosive paint" that was off-white in colour and contained ground glass.
A final coat of a pale stone colour/off-white was then applied.
"I had heard about shards of glass being put into paint but I had never come across it so that was particularly interesting to see under the microscope," said Patrick.
The bridge was completed just before Brunel's death
As part of the restoration scheme the bridge will be painted, but not in its original colour.
It has been decided to paint it goose grey, the colour of the bridge when it was Grade 1 listed in 1952.
Chris Rayner from Network Rail said: "This effort has affirmed a piece of Royal Albert Bridge's history that has been obscured under 30 coats of paint for more than a century.
"It will also be the first time that the colours of the bridge is officially chronicled for posterity."
The bridge was completed in 1859 - just a few months before Brunel's death - and it remains today as the only rail link to and from Cornwall.
When it was constructed the bridge had to be supported 80ft above water level, with a giant cylinder floated out and sunk onto the rock and the bridge's two 455-foot main spans were built on the shore, floated into position, then jacked up by a few feet per day until they reached the right level.
Detail of the original blueprint for Brunel's bridge
A total area of 20,000 square metres of paint - about three football pitches - will be blast removed before being re-painted, using a more effective three-coat painting system.
Two one metre-square patches of the existing paint layers on the bridge will be preserved for posterity - it has been re-painted on 20 occasions since it was completed in 1859.
Patrick told BBC Devon: "It was a lovely project to work on."
"First it is a Brunel bridge, which has a romance to it, and then I had the thrill of clambering over the bridge at two o'clock in the morning to get my samples.
"It's very much like assembling a jigsaw and it was an unusual project in that there was a lot of documentary evidence, although none about the original colour.
"There were also the photographs from 1859 - my job was to provide the third part to complete the puzzle."
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