At the time, a lot of people were regularly using laundry bluing as a whitening agent along with soap (not another detergent agent, real, honest-to-goodness soa

At the time, a lot of people were regularly using laundry bluing as a whitening agent along with soap (not another detergent agent, real, honest-to-goodness soap, like Sunlight Soap or Ivory Snow); it was difficult to tell those people that a more effective detergent, by itself, could accomplish what soap and bluing together had been doing. Thus blue crystals in detergent.