and configured to enhance the visibility of faults in the substrate application_number US 51314890 A description referring more specifically to the drawings fig1 shows diagrammatically an overall side elevation view of apparatus for heated pressurized fluid stream treatment of a moving substrate material to impart a pattern of tactile or visual change thereto as seen the apparatus includes a main support frame including end frame support members one of which 10 is illustrated in fig1 suitably rotatably mounted on the end support members of the frame are a plurality of substrate guide rolls which direct an indefinite length of substrate material such as a textile fabric 12 from a fabric supply roll 18 past a pressurized heated fluid treating unit generally indicated at 16 after treatment the fabric is collected in a continuous manner on a take up roll 14 as shown fabric 12 from supply roll 18 passes over an idler roll 36 and is fed by a pair of driven rolls 32 34 to a main driven fabric support roll 26 the surface of the fabric passes closely adjacent to the heated fluid discharge outlet of an elongate fluid distributing manifold assembly 30 of treating unit 16 the treated fabric 12 thereafter passes over a series of driven guide rolls 22 24 and an idler roll 20 to take up roll 14 for collection as illustrated in fig1 fluid treating unit 16 includes a source of compressed fluid such as an air compressor 38 which supplies pressurized air to an elongate air header pipe 40 header pipe 40 communicates by a series of air lines 42 spaced uniformly along its length with a bank of individual electrical heaters indicated generally at 44 the heaters 44.