*Note* At the bottom of this sheet is an excel spreadsheet that you can use to calculate lye, water, and cost of your soap making. We did not create it (see the about page for the author information) and therefore we can't offer technical support for this file. If you find it useful though, let us know.

Introduction

Soap has been made by hand for centuries. Traditionally soap was made from kitchen scraps and wood ashes. The fats used were usually animal fats and the accuracy of measurements and ingredients varied. Soaps were often “cooked”, or were put through a “hot process”. Today many soaps are mainly made from vegetable oils such as palm, coconut, and olive. This text will cover how to make cold-processed soap from vegetable oils.

Disclaimer

While this text offers a variety of information on soap making as well as step-by-step instructions, it is assumed that you have made soap before, and are familiar with the risks of, and safety protocols for working with sodium hydroxide. I assume that you will proceed with caution and common sense and I cannot be held responsibility for any harm or damage sustained from information contained in this text. This may seem obvious, but it’s important to note clearly that sodium hydroxide (lye) is extremely caustic and can cause death if consumed, permanent blindness, as well as severe burns on unprotected skin. Please see the Safety Instructions for information on how to properly handle lye.

That said, people have been safely making soap for centuries. There is also plenty of room for creativity and having fun when making soap as long as caution when working is applied.

Safety instructions

Everybody who explains how to make soap will tell you to do the following things, but not everybody who makes soap does. It is up to you to gauge the risks for yourself and to use your best judgment.

*Always wear protective eyewear (corrective eyewear is not sufficient). Lye can cause permanent blindness if it comes into contact with your eyes.

* Always wear gloves, and long sleeved clothing. Leave as little unprotected skin as possible. Chemical burns from caustic substances (such as a burn from lye) are "slow" burns, meaning that by the time you feel the burn, sufficient damage has already occurred. They tend to feel itchy or irritating as opposed to heat burns, which demand an immediate reaction.

* Always mix the Sodium Hydroxide INTO the WATER, never the other way around. To do so can cause a volcanic reaction. Always mix the LYE solution INTO the OIL. The other way around will form lye-heavy chunks of soap (which can burn the skin when used.

* Always mix the lye in a safe space with adequate ventilation – fumes are emitted when the sodium hydroxide is mixed into the water. These fumes will make you cough violently if inhaled. A safe space might be a sink (which is ideal for spills), but may not be for reasons of ventilation. A basin by a window or under a stove range hood with the fan on is ideal. If by a window, note which way the wind is blowing and place yourself out of the breeze.

* Always move carefully when walking with lye, especially if you are mixing your lye away from your work area. Keep your floor space clear to avoid tripping at inopportune moments.

* Don’t leave your lye unmarked and unattended – I know of a case where a new soap maker’s husband drank her lye thinking it was water and had to be rushed to the hospital. He sustained major damage to his esophagus and stomach.

* Be careful when measuring the sodium hydroxide crystals and make sure to clean up all spills promptly. Vinegar will help to neutralize spills or burns quickly. Sodium hydroxide crystals can cause burns when they come into contact with the skin because it will react with the skin’s natural moisture.

* Always use your best judgment and have fun!

The Basic Chemistry of Soap

Before getting to the chemistry of soap, it is worth noting that there is a big difference between handmade soap and commercially made soap – anyone who has used handmade soap will be able to attest to this, but there is also a big difference in how they are made.

The very basic idea of soap is that oil + lye = soap. For clarification, lye is a liquid solution of sodium hydroxide (or potassium hydroxide, used for making liquid soap), and water. Oil is alkaline and lye is basic. The oil, sodium hydroxide and water create a chemical reaction, which produce "soap", glycerin and water. It’s this glycerin in the finished product of handmade soap (about 25%) that distinguishes it from commercially made soap. Pure soap (remember Ivory’s 99.44 pure ad campaign?) is drying and harsh. Glycerin is very gentle, which reduces the harshness of the soap. It is also a humectant, meaning it draws moisture from the air to your skin, which helps keep your skin hydrated, even after you’ve showered.

On to the chemistry: The common alkalis used in soapmaking are sodium hydroxide (NaOH) for solid soaps, also called caustic soda; and potassium hydroxide (KOH) for liquid soap, also called caustic potash. For our purpose, we will only be using sodium hydroxide (NaOH).

The process of soapmaking that I’ll be covering is saponification, specifically cold-process saponification. The word “cold” is a bit of a misnomer, as the oils used need to be heated to a specific temperature to encourage proper saponification. As well, heat is produced through the chemical reaction (an exothermic reaction) that occurs when mixing oil and lye. Cold process refers to the fact that no heat is added during the saponification process, as is done with hot process soapmaking.

Saponification involves heating fats and oils and reacting them with a liquid alkali to produce soap and water (neat soap) plus glycerin. There is a very exact amount of sodium hydroxide to be used for each type of oil, referred to as a SAP value. A lye calculator (available online at http://www.the-sage.com/calcs/lyecalc2.php) is recommended for calculating how much lye is necessary to properly saponify the oils you’ve chosen (see the recipes near the end for pre-calculated amounts).

When making a recipe, it’s common practice to "super-fat" a soap, or include a "lye discount". This is to make the soap milder, as it will leave unsaponified oils in your finished bar of soap. It also helps to ensure that all the sodium hydroxide is properly saponified and none is left in your finished soap. A super-fat (or lye discount) of 5% is standard, and 9% is the recommended maximum. Less may cause your recipe to become lye-heavy in the case of a miss-measurement, and more will make your soap soft and prone to rancidity if left unused for a year or more.

NOTE: When made properly, there is no lye or sodium hydroxide left in a finished bar of soap. The process of saponification changes the lye and oil into soap and glycerin, with a pH of approx 8.5 to 10 when fully cured (about 4-6 weeks depending on who you talk to). The troubleshooting section will explain possible variations on soapy mess-ups and what they look like.

Do and Don’ts

* Do use only stainless steel or enamel utensils. Chipped enamel pots or any other metal alloy will be eaten by the lye, leaving the metal residue in your soap and a hole in your pot! Hard plastic utensils or wooden spoons are best.

* Do weigh all your ingredients if possible. It is possible to use volume measurements, but your results are not guaranteed. Your soap may either be “lye-heavy” or “oil-heavy”, especially in the case of small batches (less than 2 kg of soap or about 15 bars) where the margin of error is very small.

* Do resist the temptation to use your soap the same day you cut it! Allow your soap to cure at least 4-6 weeks as saponification continues to occur for the duration of this period. Your soap may burn or irritate your skin if used before the curing period is done. It will also last longer if you wait as it will dry and harden while it cures. Some people say a minimum of 6 weeks is necessary to fully cure soap.

* Don’t reuse wooden spoons or any other porous dishes for food.

* Don’t use plastic measuring cups or bowls with essential oils if you want to use the bowl later for food. It will take a long time (if ever) to get the smell out.

* Do dedicate soap making dishes if you plan to make soap frequently.

Necessary Tools (gather these before you begin)

* Soap Mould (can be a box lined with plastic, empty tetra pack or juice carton, plastic lined baking dish, etc.)

* Mixing bowl large enough for total recipe size (heat-safe, heavy duty plastic or stainless steel)

* Metal pot for melting oils if using plastic mixing bowl

* Mixing spoon

* Plastic or metal measuring cups

* Scale accurate to 1 gram (highly recommended if your ingredients are not pre-weighed)

* Rubber or silicone spatula

* Heat safe measuring cup for lye (a pyrex measuring cup or bowl works well)

* Thermometer - glass or stainless steel which ranges at least between 100˚F-150˚F or 35˚C-60˚C

* Stick blender or immersion blender (optional)

* Protective eye wear

* Rubber gloves

* Stove element or hot plate.

If you want to know more about soap making, take a workshop with us or contact us for more information.