The North Slovakian Pulp and Paper Mills (Severoslovenské celulózky a papierne), the largest papermaker in the Slovak Republic, took its present form when two individual mills combined. These were the Solo mill, established in 1880, and the Supra mill, established in 1906.
Both mills began modernization programs in the late 1970s. Some of the paper machines are now equipped with new rebuilt drives. Others, for example Board Machine no.2 in the Solo mill, and Paper Machines no.6 and 7 in the Supra mill, were completely reconstructed. All woodfree printing and writing papers produced by these paper machines are sized with AKD and filled with calcium carbonate at present.
At the beginning of the 1980s, both sulphite pulp mills (in Solo and Supra) and one obsolete sulphate pulp mill (Supra) were shut down. In 1981 a new kraft pulp mill was started up. It has a capacity of 200,000 tons per year of hardwood and softwood pulp, of which 156,000 tons is bleached. The pulp mill was supplied by the Canadian company H.A. Simons (Overseas) Ltd., Vancouver.
In 1991 Paper Machine no. 8, supplied by Voith St. Pölten (Austria), was put into operation. It has a yearly capacity of 100,000 tons of woodfree printing and writing paper. The working width of the machine is 6550 mm and the maximum working speed is 1000 meters/minute. PM no.8 and the pulp mill form the third mill, called Celpap. The entire production of PM no. 8 is sized with AKD and filled with calcium carbonate.
All Celpap papers were tested in the laboratories of the Slovak National Archives in Bratislava. They all met ANSI Z39.481984 and ISO 9706 specifications for permanence. A detailed study of the test results is being prepared for publication.