A brief intro to soap production.
WARNING: The majority of safety concerns with lye are also common with most corrosives, such as their potentially destructive effects on living tissues; examples are the skin, flesh, and the cornea. Solutions containing lyes can cause chemical burns, permanent injuries, scarring and blindness, immediately upon contact. Lyes may be harmful or even fatal if swallowed; ingestion can cause esophageal stricture. Moreover, the solvation of dry solid lyes is highly exothermic; the resulting heat may cause additional burns or ignite flammables.
The reaction between sodium hydroxide and a few metals is also hazardous. Aluminium reacts with lyes to produce hydrogen gas. Since hydrogen is flammable, mixing a large quantity of a lye such as sodium hydroxide with aluminium in a closed container is dangerous—especially when the system is at a high temperature, which speeds up the reaction. In addition to aluminium, lyes may also react with magnesium, zinc, tin, chromium, brass or bronze—producing hydrogen gas. Both the potassium and sodium forms are able to dissolve copper.
You will only need four ingredients to make basic soap plus a container.
LYE Collect hardwood ashes. To make potassium hydroxide lye, you need the white ashes from hardwood fires. When hardwood trees are growing, they draw potassium from the ground. This potassium does not burn in the fire, and is still present in the ashes after the fire. You can then leach the potassium from the ashes with water.
After every hardwood fire you have, allow the ashes to cool for a few days. Then collect the white ashes and store them in containers. You will need enough ash to nearly fill a 5 gallon barrel. Do not use ashes from softwood trees, as these do not contain enough potassium. Hardwood includes:
SOFT WATER Collect rainwater. You need to make soft water. Rainwater is ideal because it is soft and available in large quantities. Alternatively you can boil water to remove impurities and trace minerals.
With the 5 gallon barrel or container drill holes in the bottom, you fill your barrel with ashes, you will run soft water through the ashes to leach the potassium. The water needs somewhere to drain out of, so you need to make holes. Concentrate the holes near the center of the barrel so the water will drain into a bucket or other container. The container that the water runs into should be made from:
Add a layer of stones and straw or other filter. Fill the bottom of the barrel with 1 to 2 inches of clean stones and pebbles. The pebbles should be large enough that they do not fall through the holes in the bottom. Cover the stones with at least 3 inches of dried straw or grass. The straw and stones will act as a filter. The lye water will drain down through the straw and stones, leaving the ashes and particles on top.
LYE WATER Fill the barrel with wood ash. Transfer the wood ash you have collected to the barrel. Shovel the wood ash over top of the straw. Fill the barrel to within 4 inches of the top of the barrel. Prop the barrel up on sturdy blocks or rocks. Mount the barrel so the holes underneath are accessible. The barrel has to be high enough off the ground to accommodate a bucket underneath. Collect the water that drains out. After a few hours, the first run of lye water will start to trickle out from the holes in the bottom of the barrel. Let the bucket underneath fill up to within 4 inches of the top of the bucket. When the bucket is full, carefully remove it from under the barrel.
DO NOT SPILL THE LYE WATER!
TEST THE LYE WATER Test the strength. Your lye water has to be a certain strength before you can use it to make soap. The lye water will probably not be ready after a single run, but you can test it.
Run the water through again until it is strong enough. Most lye water solutions will have to be run through the ash barrel at least a second time. If your lye was not strong enough after the first run, carefully pour all the lye water back into the ash barrel. Be extremely careful not to spill or splash the lye water, as it can burn your skin.
LYE CRYSTALS In order to remove all water from the Lye Water is simple, place it in the sun so the water evaporates, what is left should be just the Lye.
RENDER FAT Heating animal fat or plant oils, heat so all solid are removed and scrape any impurities out of the fat or oils. You will need about 2 pounds of animal fat to render.
To measure proportions you can use this simple measuring amount of every 1 cup of Lye, is 8 cups of Animal Fat or Plant Oils. Mix together thoroughly so all Lye is dissolved into the fats. If you are not sure if you have blended enough, keep going.
Allow the blend to rest in a cool, dry place. After a couple days the blend should have hardened into Bar Soap!
https://www.goodhousekeeping.com/home/cleaning/a20705805/how-to-make-homemade-soap/
https://www.healthline.com/health/how-to-make-soap