Millbrook Mills were producing coarse paper by the 1840s and by 1910 were producing millboard from three vats.
Source: Shorter A H,'Paper making in the British Isles', David & Charles, 1971, p189.
The date of Millbrook Mill is unknown but by 1850 William Parry manufactured blue sugar and brown papers for handwriting, drawing and book purposes. In 1865 it was converted into a millboard mill; by 1885 it was owned by F. C. Gwynne, by 1894 the Breconshire Millboard Company and after1895 by W. G. James, who produced boards for book-binding, leather boards for soleing slippers, and trunk and engine boards.
Source: Paper-Mills and Paper-Makers in Wales 1700-1900, Alun Eirug Davies, National Library of Wales Journal, Vol XV/1, Summer 1967.
Millbrook Corn Mill (nprn 300112) is adjacent to the paper mill and used the same water supply.
B.A.Malaws, RCAHMW, 05 February 2010.