Hard soap

The water-soluble glycerin and unwanted fat residues remain in the solution (see also soap[broken anchor]).

The fatty acid salts formed during production constitute the actual soap and are effective cleaners due to their surfactant properties.

In most cases, hard soaps or products based on them are used for handwashing because they exhibit an alkaline (pH value above 7) nature and can irritate the skin when in contact with mucous membranes.

[2] For cleaning brushes, especially in oil painting, hard soap ensures extended durability of the bristles or hairs.

On occasion, water-based soap solutions are employed for pest control on cultivated plants, like against thrips and aphids.