The main function of color fixing agents is to help dyes better adhere to fibers, thereby improving the brightness and fastness of colors. Baking soda is an effective color fixing agent. When dyes combine with fibers, baking soda can react with acidic substances in the dyes to form stable compounds, making the dyes more firmly fixed on the fibers.
link:https://www.chinabakingsoda.com/sodium-bicarbonate/china-high-quality-sodium-bicarbonate.html