HARROGATE art conservator, Andrew Stewart, has spent four weeks painstakingly peeling back layers of dirt to restore two valuable narrative paintings.

Going North and Coming South, by the Victorian artist, George Earl, belong to the National Railway Museum in York.

They tell the story of a group of friends travelling from King's Cross Station to Scotland for the August grouse shooting season and returning from Perth Station a month later with their spoils.

This week, after cleaning, they went back to the museum which bought them in 1990 for £750,000 with the help of the National Heritage Memorial Fund and the National Art Collections Fund.

Said Mr Stewart: "A project like this requires a lot of detective work to find out what has been going on over the years, pinpointing previous restoration work and any ageing of the paint.

"With the benefit of ultra violet light and x-ray photograpjy, we were able to reveal a lot of pentimenti, or ghost images, where the artist had painted over a mistake or changed his mind.

"We also discovered that the signature on Coming South had been altered during a previous restoration."

Matching the pigments used by the nineteenth century artist was also a challenge. Old favourites like rich dark brown made from ground-up Egyptian mummies and Indian yellow, distilled from cow urine, are now a little hard to come by.

Said Mr Stewart: "Oils are no longer used in restoration because they are too unstable. Instead we use very fine layers of synthetic varnish mixed with ground pigments to imitate the colours in the 100-year-old paint."

George Earl (1824-1908) is chiefly knwon as an animal and sporting painter. The museum pictures were originally commissioned by the brewery magnate, Sir Andrew Barclay Walker, and rescued nearly 100 years later from a pub in Liverpool.