Breathing and bleeding describe different process functions: providing an air-evacuation path and absorbing resin where the process requires it. A process consumable can have a defined role in either or both. Specify the actual product and arrangement rather than assuming that similar-looking fabrics are interchangeable.
Gurit’s prepreg processing guide discusses breather materials in the bagging arrangement. That information belongs to a defined process context. A generic request for “white felt” does not identify the required material, its position or its approved use with the proposed resin system.
Keep auxiliary layers distinct
Release film, peel ply and a breather or bleeder are not simply different names for the same layer. The manufacturing documentation should identify the arrangement and the purpose of its components. A purchaser normally needs the agreed supplied condition and required evidence, not an improvised bagging recipe.
Review changes that affect the requirement
If a consumable or arrangement changes, the manufacturer should assess it under the agreed process controls. Where the order requires notification or qualification evidence, record that scope clearly. An auxiliary-material description is not proof of the resulting laminate’s quality; the finished component still needs its own inspection and acceptance requirements.
Further reading: Gurit: prepreg processing guide.