Laundry bluing contains the dye called Prussian blue which was manufactured in the 1700's and the process of laundry bluing goes back countless years ago. Clothing manufacturers as well as makers of towels, linens and other fabrics engage in the process of bluing.
How do you do laundry bluing at home? If you are using a washing machine, just wash the white clothing and fabrics normally and in the final rinse, add a few drops of bluing agent. The same may be done through hand washing but you may need to do another round of rinsing without the bluing agent.