Mr Cranston says he has catalogued every Scottish brick, external they have found or been given.
“As far as Scottish industrial history goes this collection is unique,” he said.
“We were at the forefront of the industrial revolution. It was all about industrial processes of heat and steam.
“Wherever there was heat you had to protect whatever was being heated by the direct heat source so you would have fire bricks in between.”
The retired police sergeant said there were still thousands more examples of Scottish bricks to find.
“We are adding bricks every week that we haven’t recorded before,” he said.
The 62-year-old said when he first started in 2010 he asked the National Museum of Scotland how many different stamped Scottish bricks there were and was told 350.
“Obviously we have now proven that’s way out,” he said.
He added that he was very proud of their collection.
“It’s a unique way of collecting industrial history, which interests both of us,” he said.
“I can’t even begin to think how many hours have gone into the website to record the bricks let alone searching for them and the travelling we’ve done.
