The most difficult part of early soapmaking was determining if the lye was the correct strength. The 'lye water' was considered the proper strength to make soap when an egg or small potato placed in the solution floated about halfway beneath the surface of the solution. If the egg or potato floated on top, the lye was too strong. If it sank quickly, the lye was too weak. Some early soapmakers used goose or chicken feathers to test their lye. If a feather inserted in the lye water began to dissolve in it, then the lye water was at the right strength.
During World War I, commercial soap, as we know it today, came into existence. The injuries of war brought an increased need for cleaning agents. However, at the same time, the ingredients needed to make soap were scarce. German scientists created a new form of 'soap' made with various synthetic compounds and as a result, detergents were born.
Most commercial soaps available today are actually detergents, which are made with petroleum by-products. Since these 'soaps' are detergents, by law they cannot be called soap. Chances are that when you see a soap called a 'body bar' it's not soap at all.
After World War I and until the 1930's, soap was made by a method called batch kettle boiling. Commercial soap makers had huge three story kettles that produced thousands of pounds of soap over the course of about a week. Shortly thereafter, an invention called continuous process was introduced and refined by Procter & Gamble. This process decreased soap making production time to less than a day. Large commercial soap manufacturers still use continuous process.
Commercial soap manufacturers also learned that they could remove the natural glycerin in soap which gives it moisturizing properties. They sell it or use it in other higher priced products like the moisturisers and creams you need when their soap dries out your skin. Removing the natural glycerin also extends the shelf life of the soap so that it can sit in the warehouse or on store shelves for many years.
Today there is a heightened awareness of the possible adverse effects of many of the synthetic additives and chemicals in commercial soap. Educated consumers are turning to all natural products like ours. Even large companies are starting to advertise 'natural ingredients' in their products.
But be very careful, the addition of one or two natural ingredients does not make a product 'all natural'. It's near impossible for large companies to create natural, handmade soaps.