The insoluble calcium and magnesium salts formed from the fatty acid portion of soap when it combines with minerals in hard water; it is commonly referred to as soap curd.
The use of the word lime in this term may come from the fact that limestone areas generally foster hard water, or from the fact that the words lime and calcium are closely associated. Calcium and magnesium fatty acid salts are highly insoluble and precipitate immediately on formation. Since they tend to agglomerate (cluster together), they form curd-like masses. They also tend to adhere to surfaces, thus causing filming or deposits, such as bathtub ring.
The problems lime soap causes spurred the development of mechanical water softeners, packaged water softeners, and the technology leading to new surfactants and builders and detergent products based on them.
See Also: Carbonate Hardness Bicarbonate Hardness Hardness Hard Water Total Hardness (TH) Soap Curd Soap Soap Curd Soap Club Soda Community Water System Zone of Saturation Bottled Artesian Water Bottled Distilled Water Bottled Fluoridated Water Bottled Mineral Water Bottled Natural Water Bottled Spring Water Brackish Water Brine Internal Water Treatment Ion Exchange Aesthetic Contaminants Health Contaminant Drainage Basin Drinking Water Drinking Water Standards Municipal Water Permutit Process Phosphate Potable (Drinking) Water Etching External Water Treatment United States Pharmacopeia (USP) Water Softening WFI Sulfur (S) Safe Drinking Water Act (SDWA) Safe Water Sewage Silica Sodium Carbonate Softened Water Soft Water Permutit Process Phosphate Water Softening Sodium Carbonate