How to Make Lye. Lye is a caustic soda commonly made from ash. Lye is sodium hydroxide in solution and is used to make soap and also to unclog drains. Lye has a very high base and will burn the skin upon contact. You can make your own lye, but should exercise caution during the process.
Make lye water from wood ashes. The concept is simple but the mechanism may require a bit of ingenuity. Water must drip gently down through a container of wood ash. The source for wood ash can be a fireplace, fire pit or campfire. Hardwood ashes will produce lye that can be used to make hard soap bars.
Burn wood at a high temperature. The fire should reduce the wood to white ash. After the fire has cooled collect the white ash in a sealed container to keep it dry and uncontaminated. When making lye, use plastic or ceramic as the caustic soda will erode metal containers. Store the wood ash.
Collect rain water or stream water. This water is less contaminated and is the ideal source for traditional lye making. The proper water is essential to the process.
Place the wood ash in a bucket with a tap or other drain hole. Pour a half bucket of hot water over the ash. Slowly add cool water until the water drips from the container. Add more ash and water again until the ash floats. Let stand overnight.
Drain out the brownish water into a safe plastic container. Pour this water over the ash mixture again. Let this brownish lye water drain into a safe container. After the lye water drains completely, add more cool water to the mixture and collect this weaker lye water in a different container. This brownish liquid is the lye water used for traditional soap making and for other industrial uses.