Science, Tech, Math › Science How to Make Soap Share Flipboard Email Print chizu/Getty Images Science Chemistry Projects & Experiments Basics Chemical Laws Molecules Periodic Table Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated March 18, 2017 These are the instructions for making your own gentle hand or face soap. It's work, but worth the effort! This takes about 1 day to complete. Materials 4 kg (9 lb) suet (tallow)350 g (12 oz) lye750 ml (3 C) water500 ml (2 C) lemon juice7.5 ml (.25 oz) fragranceGlovesWooden spoonVentilated work areaMolds/glass baking dishes Instructions on How to Make Soap If you are using a pure fat, such as coconut oil or olive oil, you can skip stepping 5. Coconut oil yields a soft, quick-lathering soap. Olive oil and other vegetable cooking oils yield a soft soap that never completely hardens.Render the tallow by cutting it into chunks, placing it into the large pot, covering it, and heating on medium heat until it is melted. Stir occasionally.Cool the fat to below the boiling point of water. Add a volume of water equal to that of the fat. Bring the mixture to a boil. Cover and remove from heat. Let sit overnight.Remove the fat from the pot. Discard non-fat gunk (scrape it off of the bottom of the fat) and any liquid.Measure 2.75 kg rendered fat. Cut the fat into tennis-ball size chunks and place the pieces into a large bowl.Set up all of your materials. Ventilate the area (or work outside), put on safety gear, and open all containers.Make soap :-) Pour the water into a large glass or ceramic bowl (not metal). Carefully pour the lye into the bowl and mix the water and lye with the wooden spoon.The reaction between water and lye gives off heat (is exothermic) and vapors that you should avoid breathing. The spoon will be somewhat degraded by the lye.Once the lye is dissolved by the water, start adding the chunks of fat, a bit at a time. Keep stirring until the fat is melted. If necessary, add heat (put on a low burner with ventilation).Stir in the lemon juice and fragrance oil (optional). Once the soap is well mixed, pour it into molds. If you use glass baking dishes for molds, you can cut the soap into bars after it has become firmer (not hard).The soap will harden in approximately an hour.You may wrap the finished soap in clean cotton rags. It can be stored for 3-6 months in a cool, well-ventilated location.Wear gloves when washing your equipment, as there may be some unreacted lye remaining. Wash in very hot water to help melt away the residue. Useful Tips Adult supervision required! Wear gloves and protective eyewear and cover exposed skin to avoid accidental exposure to the lye. Keep out of reach of children!If you get lye on your skin, immediately wash it with lots of cold water. Read the cautions on the container before opening the lye.Don't measure the lye. Instead, adjust the soap recipe to accomodate the container size of the lye.Cooking oils are sensitive to air and light, and soap made from cooking oils will spoil in a few weeks unless it is refrigerated.Volatile fragrance oils or even dried herbs or spices may be added to the soap to scent it. The fragrance is optional.