Abstract
Most of the white cloths made of synthetic fibers decrease their whiteness by repeating alternately wearing and washing, and their original whiteness cannot be recovered by treatment with either optical whitening agent or chemical bleach.
The authors thought that this fact was caused by fatty soils in water for a wash, and experiments were carried out to make this point clear. Hydrous lanolin was added into water in place of human skin lipids. Four kinds of soil solutions prepared from carbon black, lanolin, and detergent were used.
The results obtained were as follows :
1. In the laundering process, lanolin in the soil solution largely reduces whiteness of the cloths made of hydrophobic fibers.
2. Detergents in soil solutions always lessen the amount of soils depositing on the cloths.
3. The contamination made by fatty and carbon black soils on the hydrophilic fabrics, such as cotton and modified polyester, in the soil solution which contains detergents is nearly equal to the contamination made solely by carbon black in the soil solution containing detergents.
4. It appears that ester type compounds in fatty soil decrease whiteness more than other types.
