Hard soap

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Related to Hard soap: soft soap
any one of a great variety of soaps, of different ingredients and color, which are hard and compact. All solid soaps are of this class.

See also: Soap

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
He then donned his waistcoat, and taking up a piece of hard soap on the wash-stand centre-table, dipped it into water and commenced lathering his face.
The high amount of sodium (27.56 mg/l) contributes to the saponification reaction that produces hard soap. This explains why the FOG deposited samples are layers of white and hard material with a soft surface that is similar to any soap curds that form after a saponification reaction.
In addition, as hard soap will have a lower solubility, it will prolong the shelf life of the soap itself and vice versa for softer soap, but it will also make the soap easy to crack 10].