Mineral fiber webs.

A continuous process for forming a layer of bonded mineral fibers, comprising an upper layer interwoven with a lower layer having a lower density than the upper layer wherein each layer is a network of bonded nonwoven fibers, which process comprises providing a continuous web of mineral fiber containing binder, separating the web in the direction of the depth in the lower and upper subnets, subjecting the higher thickness compression and greater lengthwise compression than is required to compensate for the thickness compression subnet, and subjecting the upper longitudinal stretching and / or lower longitudinal compression subnet so subnet as the lower and upper subnets have substantially the same overall lengthwise compression, and then rejoining the subnetworks to form an uncured batt wherein the upper sub provides the upper layer of the batt, and curing the binder.