Soap is the product of heated oils and lye that through a process called "saponification", makes soap. The lye solution has to be strong enough to dissolve most of the oils leaving just enough oils to make the soap moisturizing to the skin. Oil dissolves oil which is why soap works best to clean our skin gently, without stripping your skin like chemical detergents will. Soap can be infused with many different liquids like teas and milks. They can be colored with many different natural things like annatto seeds for yellows and oranges, alkanet root for purples and oxides for other colors like green and red and pink. Add different flowers or oatmeal or coffee grinds for texture. You can add clays, salt and charcoal them depending on the effect you want to achieve. I love to be creative!
Soap is like wine, the longer it is aged the better the bar, the bigger the lather and the longer it lasts. A good bar of soap needs to be aged before it can be enjoyed.
Soap, especially handmade soap is fragile, but will last for a long time if treated properly. The first rule of soap care is to keep the bar dry between uses. The best soap dish is a plain untreated wooden dish that will wick away moisture and will dry fast between uses. I have to admit as time goes on I get more of a stickler for clean hands, so I wash my hands a lot. Even under this regimen the bar beside my sink will last a month or longer with my wooden dish.
Store your handmade soaps in a cool, dark and dry place until you are ready to use them. That way they will not fade in either colour or scent. Natural colourants just don't stand up to sunlight the way commercial soaps can.