In the paper industry it is common practice to make so-called hand sheets of pulps to determine physical and optical properties before going to production of from the production pulp. One of the systems to produce these hand sheets is the Rapid-Köthen method. In this method a container with on the bottom a screen is filled with the pulp dilution the after homogenizing the pulp in the container a valve on the bottom is opened and the water is drained leaving the pulp on the screen. The wet sheet is transferred from the screen to the dryer by means of the carrier board. A paper cover sheet is placed on top. In the dryer the sheet is dried between the carrier board and paper cover sheet. The carrier board and paper cover sheet are removed when the sheet is dry. After conditioning the sheet is ready for testing.
Carrier boards are circular sheets of bleached lined folding boxboard, without colorants or fluorescent whitening agents, having a diameter of 240 mm, a grammage of 200 g/m², and a well-sized surface. The paper cover sheets are circular sheets of well-sized calendered paper, with a grammage of 65 g/m² and a diameter of 205 mm.
The carrier board and paper cover sheet are used with a hand sheet former for physical testing conform ISO 5269-2: Pulps - Preparation of laboratory sheets for physical testing - Part 2: Rapid-Köthen method.
Both the carrier boards and the cover sheets are packed in multiples of 1000 sheets. For larger volumes special prices apply.
There are a large number of producers of Rapid-Köthen sheetformers, e.g. TMI, Regmed, L&W, Haage and PTI.