R & J Dempster was established in 1884 by brothers Robert Dempster and James Dempster, with support from their fathers company Robert Dempster and Sons. The business operated from Oldham Road, Manchester. The company joined with Glengarnock Iron and Steel company in 1894 to form Glengarnock Chemical company.

The firm specialised in structural ironwork such as coke ovens, blast furance recovery plants, gaswork installations, elevators and conveyors, condensers, exhausters, steam engines and pumps. By 1914 the company had 632 employees.

In 1962 Ronald Thomas Newsham bought the entire capital share of the company. In 1967 Chairman Newsham was put on trail accused of committing serious accounting fraud against the company.

On 25th July 2016, the company was restored by order of the court. The court deemed that the company had continued in existence as if its name had not been struck off. On the 14th December 2021 the firm was dissolved via compulsory strike-off.