J-Box is one of the popular machines generally used in scouring of cotton fabrics. J-box is essentially a J-letter shaped stainless steel chute with large fabrics holding capacity. The fabric is fed from one end & taken out of the other in contrast to a kier where it is first in last out. The J-box has a polished inner side and it is insulated to minimize heat losses.

The fabric after saturation with liquor is fed from the top and taken out from the lower end. Depending on fabric speed (150-300 m/min) and the capacity (4,500 m) a residence time of 60-90 min may be provided. Fabric may be heated at the entry to the J-box. Liquor ratio 1:1. After coming out from the J-box, the fabric is sent to a washer. In the schematic below, the flow of material for designing in a J-box.