Bluing squares are a traditional ingredient in folk magic.  They are added to cleansing sprays, floor washes, and even baths to draw luck and protection, remove negative entities, and enhance spiritual energy and divinatory abilities. 
 
Modern spiritual workers have adopted the use of these squares to replace copper sulfate, which replaced the even older use of pure indigo.
 
Bluing and camphor can be placed together in a glass of water with a submerged Evil Eye charm near the entrance to your home to create a barrier against negativity.