In a hard-to-reach corner of the first-floor drawing room, small pieces of wallpaper have helped to unlock York Mansion House's Georgian past.
A £1.3m restoration is under way at the 300-year-old Lord Mayor's residence, which involves repairing the windows, roof and redecorating.
Stripping away the yellow wallpaper from the 1990s, workers found the walls underneath to be mostly bare.
However, seven layers of wallpaper on a thin sliver of wall revealed the room's decorative history, dating back to the 18th Century, for the first time.
Hannah Bellerby, a senior architect from Buttress Architects, says the drawing room is one of the key areas the team are looking at.
"We thought we had nothing to go on and didn't know where we were going to go with the works," she says.
"Then what we found, really interestingly in the corner of the room, was intact wallpaper pieces."
The team brought in an expert to remove 12 samples of the wallpaper, before separating the layers and magnifying them.
"Each wallpaper was identified by what kind of paper it was, what pigmentation it would have had and what pattern it would have had," Ms Bellerby says.
"That gave us a really clear idea of the changing styles and tastes of this room, which is information we didn't have before.
"It is a brand new discovery."
Although old black and white photos of the house exist, the new samples allow the team to colour in the past.
In 2017, an earlier refurbishment project found pieces of wallpaper from the mid-1800s underneath the floorboards, which would have been printed in white and gold.
The oldest layer of wallpaper from the new sample is a flock paper, made with a mixture of chalk and lime with a pigment in it.
A stencil would have been put on a wooden block in varnish, according to Ms Bellerby, and then bits of wool would have been put on top.
"We know from the colours seen in that sample that it would have been a red flock wallpaper," the architect says.
"That type of wallpaper was really popular in the Georgian era in the late 18th Century.
"We think it was either the first or a very early decorative scheme in this room."
As well as wallpaper, paint throughout the house is analysed to uncover previous colour schemes.
Ms Bellerby points to a patch of wall in the hallway, which is also being redecorated.
"This is one of the mechanical exposures we've had done," she says.
"They mechanically expose the scheme of colour we're looking to get to, which involves cutting into layers of paint to get back to this layer here.
"That allows us to get a really accurate colour match to the exact scheme we're hoping to reproduce."
Underneath is an olive green colour, with bits of stencilling.
Architects are hoping to restore the Mansion House back to its original Georgian appearance.
It follows work to the basement areas and original kitchens.
Although the external work will finish in December, the house will open to the public again in summer.
"It's always exciting to see this stage, even though it looks a bit dusty and everything is covered in sheeting and boarding," Mansion House manager and curator, Richard Pollitt, says.
"In August, it will all be finished and looking quite new for our 300th year Georgian festival."