Abstract: The disclosure relates to the production of a mineral fiber product for example to replace asbestos fibers in different products. In the method of production, at most 7% by weight of mineral fibers is dispersed in water which contains a wetting agent, undispersible material being then separated and the dispersion being then mechanically dewatered to a dry content of from 30 to 70% by weight and a fiber density of from 200 to 400 kg/m.sup.3. In a subsequent, separate stage, the fibers are redispersed in water substantially without the addition of wetting agent, are provided with possible additives such as cellulose fibers, are shaped, dewatered and dried.

Abstract: A sample of mineral fibers is dispersed in a liquid and viscosity of the dispersion is measured. The viscosity value provides a rapid measure of the length of the fibers. The measurement is sufficiently rapid that adjustments can be made to operating conditions during a production run to ensure the production of fibers of uniform length characteristics.

Abstract: A method is provided for controlling the surface weight of a mineral wool mat in a process in which fibers of mineral wool are produced by spinning a mineral melt and the mineral wool formed from the fibers is transferred to a collection device using a stream of gas which is separated from the mineral wool in the collection device, the mineral wool forming a mat on a collection band. The method concerns measuring at least two variables which influence the amount of mineral wool formed per unit time and predicting, based on these measurements, the production of mineral wool at a predetermined future point in time. The surface weight of the mineral wool mat is measured along with the speed of the collection band and these quantities are used to determine the actual amount of mineral wool produced at the predetermined time.