General view of the coupling tubs used for the manufacture of azo dyes at the Althouse Chemical Company plant in Reading, Pennsylvania. In a typical manufacturing process for azo dyes, coupling tubs are recessed in the floor, as seen here, with tubs of diazotized amine solution positioned above. After the diazotized amine solution flows into the tubs and coupling occurs, a precipitated dye slurry is transferred to blowcases on the floor below and blown through filtration equipment to produce dye cake.

Based in Reading, Pennsylvania, the Althouse Chemical Company was founded in 1915 by C. Scott Althouse (1880-1970) as a small, family-owned firm specializing in fabric dyes of a superior quality and class. In 1954, the Crompton & Knowles Corporation of Worcester, Massachusetts acquired Althouse, which continued to operate as a division of Crompton & Knowles and a leader in the specialty dyes industry.