"Properly made handmade soap has no lye left in it but cannot be made without it. Our ancestors made up a weak lye solution from wood ash to produce their handmade soap." - a soapcrafter
This statement is true. Many people think that lye is a horrible "chemical" that is best to avoid in soap. But let me ask you this....does your soap lather? If yes, then it is made with lye. It is impossible for it not to be.
There are no lye soaps on the market, but they are made with harsh detergents.
But natural soap (void of these manufactured detergents) is great to use everyday and can be very moisturizing.
The most common practice of soap-making is 'cold process'. With this method, the lye(sodium hydroxide) and fats are mixed then set in molds to cure. The curing process can take up to 3 weeks. After this time the soap is safe to use. This is great to make lots of batches in a small amount of time. Also many crafters use this method to take advantage of the artistic capabilities it offers. The visual effects that are possible are endless. You can swirl, use a vast array of colors and the soaps can be molded in many shapes that are not possible with 'hot-processed' soaps. But the crafter must be attentive to the curing process. The lye and fats come together(saponify) to create soap, so this process must finish before exposing to skin.
I have used the 'cold-process' method many times. And it produces a great bar of soap. I prefer the 'hot-process' because after my soap has cooked, I know it is ready for use by the next day. The saponification has finished and it is safe to use.
Another soaping method is "melt & pour". This is commercial soap offered in large blocks that can be melted down to add herbs, scents and colors. Many hobbyists use this method to produce personalized soaps. But they are not handmade.