Mrs. Stewart?s® Bluing is a simple, concentrated blue liquid that optically whitens white fabric. The white which is the brightest of whites is one which has a slight blue hue. MSB is nontoxic, biodegradable, non-hazardous and environmentally friendly.Other uses include, making a salt crystal garden, whitening hair and pets, detecting plumbing leaks, salmon fishing, brightening pool water, plus other uses.