Home Resources Fact Sheets How to Make Natural Soap with Vegetable Oil and Lye

Join our mailing list


Events Calendar

Click Here for link to calendar to see upcoming ECOSF events

How to Make Natural Soap with Vegetable Oil and Lye


  • Ceramic, enamel, or stainless steel saucepan large enough for all your ingredients, the “soap making pan”

  • Smaller saucepan or heat resistant glass container to melt your solid oils in

  • Heat resistant glass container to measure the water and mix the lye into

  • 2-3 stirring tools (heavy duty rubber, silicone, stainless steel, or wood)

  • Good quality scale (that can measure within 1 gram and ½ ounce)

  • Two quick read thermometers that measure from 0-220 degrees Fahrenheit

  • Mold for pouring soap into (can be wooden box lined with wax paper or waxed paper container like a milk carton)

  • Sharp, thin paring knife for cutting and trimming finished soap

  • Safety goggles and gloves

  • Newspaper or material to cover work area

  • NOTE: Avoid using aluminum, tin, cast-iron, weak/soft plastics, and know that over time, wood can deteriorate and splinter into your soap, and glass over a longer period of time will start to dissolve. It is best to designate “soap making” equipment from other cooking equipment, though after a thorough washing and rinsing, it should pose no problem to use the equipment interchangeably.



40 Bar Batch

3 lbs. cold, distilled water

473 grams of sodium hydroxide

4 lbs. olive oil

2 lbs. 8 oz. coconut oil

1 lb. 8 oz. palm oil (or other oil)

30 grams grapefruit seed extract (optional)

45-50 grams of essential oil (optional)

4 Tbs. extra nutrients (optional)

7 Bar Batch

8 oz. cold, distilled water

79 grams of sodium hydroxide

10.5 oz. olive oil

6.5 oz. coconut oil

4 oz. palm oil (or other oil)

5 grams grapefruit seed extract (optional)

7.5-8 grams of essential oils (optional)

2 tsp. extra nutrients (optional)


A little about the ingredients…

Water – Acts as a solvent to give the sodium hydroxide (lye) more surface area to react with the oils, yet remains unchanged after saponification. Does not have to be distilled, you just can’t use ‘hard’ water.

Lye – Can refer to sodium hydroxide in crystal form, or as a liquid solution. Available at many hardware stores in 13.5 oz. containers sold as a drain opener. Make sure it is 100% lye without additives, contact manufacturer if unsure. Lye is caustic soda that is a corrosive alkali that will burn skin, eyes, and soft material on contact. The more lye added, the more heat and expansion will occur so be careful. Pour slowly in small amounts and avoid inhaling fumes. Gloves, goggles, and careful maneuvering are all that is required to avoid a problem. Once mixed with oil and saponifies, is no longer harmful.

Olive oil – Makes a mild soap with little lather, while being a great moisturizer that attracts external moisture, and holds it close to the skin, and forms a breathable film to prevent loss of internal moisture. Shares these traits with jojoba oil and Shea butter, all of which are known as humectants. Extra virgin olive oil is great but unnecessary for soap making. Consider less expensive alternative grades (refined Grade A, Grade B refined, and Pomace). A higher concentration of olive oil means a longer mixing time to saponify. Also great because it is produced here in California so it is local!

Coconut oil – Necessary for creating a hard bar with a good amount of lather, though in excess, can be drying for some skin types. If purchasing in bulk, make sure to select a melting point no higher than 76 degrees F. Look for organic and fair trade!

Palm oil – Pressed from the fruit of the oil palm (different species than the coconut palm), it lends similar qualities to coconut oil, and is great in combination with coconut, olive, and other oils because it is less water soluble and produces a nice hard bar that keeps its firmness throughout use, as well as saponifying quickly. Hard to find in bulk, look for fair trade & organic!

Avocado oil – Is highly therapeutic because it has a high amount of unsaponifiables (the oil that doesn’t mix with lye during saponification which remains intact and full of protein, amino acids, and relatively large amounts of vitamins A, D, and E. It’s known for regenerating cells, soften body tissue, and heal scaly skin and scalp. Only a little oil in the recipe is necessary to be very effective. It can be added up to ¼ of total oil reducing either the olive oil or coconut oil, or both, to compensate.

Jojoba oil – Resists rancidity and highly stable; a very good moisturizer and for helping repair damaged skin. Like olive oil, a thin layer can help regulate evaporation and dryness in the skin. Look for North American grown Jojoba oil.

Extra Nutrients added after mixing and before adding essential oils: Shea butter, Apricot kernel oil, Sweet Almond oil, Wheat germ oil, Castor oil, Evening Primrose Oil, Borage Oil, Rosehip seed oil, Honey, Aloe Vera, Ground Oatmeal, Flaxseed, Cornmeal, Alfalfa meal, and other grains.

Grape seed Extract: Mixed in before nutrients and essential oils to act as a natural preservative.

Goat Milk – Added to lye water at around 80 degrees before mixing with oils. Just a small amount necessary for moisturizing effects.



Basic Steps:

  1. Set out all soap making equipment and have it ready for use. Measure out essential oils, preservatives, and extra nutrients if using them and set aside in separate containers.

  2. If using a cardboard/wooden box for a mold, carefully line with waxed paper and mitre the corners. Milk cartons should be laid on their side with one side cut open and the top folded in and taped.

  3. Put on safety goggles and gloves.

  4. Weight out sodium hydroxide and set aside.

  5. Set heat resistant glass container on the scale and weight out required amount of water.

  6. Wearing goggles and gloves, carefully add the sodium hydroxide to the glass container and stir briskly until completely dissolved. CAUTION: This is potentially the most dangerous stage of the soap making process. It will quickly reach a temperature over 180 degrees F and give off toxic fumes momentarily. The greater the measurement, the hotter it gets and the stronger the fumes. Be very careful. You want the lye to be just above 80 degrees F before adding to the oils so setting the container in a dish of cold water or ice water will bring the temperature down faster.

  7. Place soap making pan on scale and weigh out the liquid soap making oils.

  8. Place smaller saucepan on scale and weigh out the solid fats, to be melted before adding to the liquid oils, and set aside.

  9. Gently heat the solid oils to between 80-90 degrees F and add to the liquid oils in the soap-making pan. The total mixture should be just above 80 degrees F.

  10. Wearing goggles and gloves, slowly drizzle the lye into the oils, stirring the mixture briskly.

  11. Continue to stir briskly, circling the pan and cutting through the middle of the pan with your spatula to keep as much of the solution as possible in constant motion. Once a small amount of the soap drizzled across the surface leaves a trace pattern before sinking back into the mass, the soap is ready.

  12. Stir in nutrients, then essential oils if using them, stirring swiftly and thoroughly.

  13. Once the oils are evenly distributed and the soap mixture is uniform in appearance, quickly pour the soap into the frame, moving from one end of the frame to the other to evenly distribute the soap within the frame for uniform bars. If you’re concerned with aesthetics, don’t scrape any residue from the sides of the pan.

  14. Cover the filled wooden frame with a piece of plywood, or place the milk carton in a reused plastic grocery bag. Cover with a blanket or a few towels to insulate the newly prepared soap through the saponification process. Leave undisturbed for 18-24 hours.

  15. For near perfectly symmetrical bars, use a ruler and a paring knife to lightly mark lines for cutting into the mass, but don’t cut all the way through. Once you are satisfied that the lines are straight and uniform, cut through lengthwise and crosswise to the bottom of the frame. If you’re less concerned with uniform bars, or you’re using a reused milk carton, simply tear the sides of the milk carton down to expose the hardened soap and pull it out of the carton. Cut as desired.

  16. Slice a thin sliver (1/16th of an inch) off of the top of the bars to remove the powdery white soda ash that develops on the exposed edges. Lay the bars out on cardboard, or a paper bag so that all sides of the bars can breath as they cure. They should be ready to use or wrap as gifts in about 3-4 weeks.


Adding Scents


While the sensory indulgence of jasmine and other exotic scents are nice, they don’t contribute to the healing properties of vegetable based oil soaps and some skin types are sensitive to essential oils, which is the only way you would want to scent your soap. If you decide to do so, expect to spend at least $30 or more on good, pure essential oils for a recipe for 20 or more bars. It can be a delicate process as the essential oils are highly reactive and can seize up in the soap and not produce a uniform bar. Always add essential oils last, stirring in thoroughly before pouring into mold.


Family of Scents:

Woody: Sandalwood, Cedar*, Rosewood, Juniper berry, Patchouli

Evergreen: Swiss Pine*, Mountain Pine*, Ocean Pine*, Stone Pine*

Green: Basil*, Cucumber, Violet, Mimosa

Herbal: Rosemary*, Marjoram, Dill, Tarragon, Coriander, Fennel, Caraway Seed, Clary Sage

Fruity: Apple, Peach, Strawberry, Apricot, Black Currant, Cherry

Citrus: Lemon*, Orange*, Tangerine, Bergamot, Grapefruit, Lime, Verbena*

Floral: Carnation*, Gardenia, Honeysuckle, Lavender, Hyacinth, Chamomile, Lilac, Rose, Geranium, Lily, Iris

*may be irritating to some skin types – use cautiously



Much of the facts and specifics from this info sheet were derived from Susan Miller Cavitch’s The Natural Soap Book

Mountain Rose Herbs – Organic supplier of bulk oils and other soap making supplies www.mountainroseherbs.com

The Essential Oil Company – Organic supplier of bulk essential oils and more www.essentialoil.com

Ye Olde Soap Shop – California Soap Making Supplier www.soapmaking.com