There are some safety issues to consider. Working with corrosive substances is dangerous, and if some basic rules are not followed, accidents can happen.
Always work with gloves, wear long-sleeved clothes, possibly with an apron or robe over clothes. Protect your eyes with goggles, wear gloves even when washing dishes and utensils after the preparation, because the soap composition is still reactive when fresh.
Whenever the hydroxide solution (lye) is prepared, caustic soda should be added over water and not the other way around. Even so, the prepared solution will heat up and emit vapors that must be avoided from being inhaled. Prepare the hydroxide solution in well-ventilated areas, possibly under a kitchen hood. Allow the hydroxide solution to cool to a temperature as close as possible to that of the oils used in the recipe. Containers in which hydroxide solution is prepared must be resistant to high temperatures and not be used for other purposes.
For your safety, keep a bottle of vinegar on the work table during soap preparation. In case the hydroxide solution spills out, you can neutralize it using vinegar.
When mixing with the blender, avoid inserting air bubbles into the composition and avoid spilling or spraying the composition on the workspace. Protect the table you are working on with a tablecloth or other materials, as the hydroxide solution can dull or stain surfaces.
When preparing the soap, make sure that there are no children or animals around you that could come into contact with the substances. Label your containers with solutions or substances, and keep them out of the reach of children.
In order to prepare cold process soap, you will need the following tools/equipment:
- an electronic (kitchen) scale, preferably one that has an accuracy of at least one decimal place, if you need to measure less than 1 g
- a vertical blender for mixing the composition. In case you do not have one available, you can also use a whisk, only the process will take considerably longer.
- gloves, because corrosive substances are used, the hands need to be protected
- goggles to protect the eyes from possible splashes
- heat-resistant containers, stainless steel or enameled pots, higher temperature-resistant plastic containers used to mix the composition, to melt or heat the oils
- Berzelius beakers or other heat-resistant containers used to prepare the NaOH solution, which can reach a temperature of 100°C
- silicone spatulas or plastic/stainless steel spoons, with which to dose and mix the ingredients
- vessels/bowls for weighing different ingredients
- molds or silicone molds for pouring the soap composition
It is recommended that the vessels and tools used for soap making to be used exclusively for this purpose. It is also good to prepare more containers than necessary, in case you need to weigh or portion different ingredients. The volume of the containers in which the soap composition will be mixed is recommended to be higher than the final composition, because during mixing with the blender, the composition may splash out.
Other equipment you may need:
- dishes/pots for water baths
- stove to heat the ingredients
- suitable thermometer, to be able to measure the temperature of liquids
- mini-mixer to mix dyes or other additives
- Pasteur pipettes for dosing liquid ingredients in small volumes
- sieve for powdered substances
- soap cutting tools, knifes, wooden or plastic cutting boards
- paper towels and kitchen cloths for cleaning
- a vial with a pump, filled with 70° sanitary alcohol or 96° pure ethyl alcohol for spraying the poured soap, and for cleaning the workspace
Before you start preparing the soap, place all the utensils and equipment on the work table, to be at hand. Place the scale in the middle of the table, and the containers you will be working with around it.
Weigh the necessary substances for the recipe: for example the caustic soda, distilled water and oils. After weighing, the oils can be placed in a water bath or in a microwave oven for melting or heating.
Once you have all the materials weighed, you can move on to dissolving the caustic soda in water.
The equipment that is no longer needed is then removed from the work table, and the containers in which the soap composition will be made are prepared. Place the mixing bowl in the center of the workspace. The heated oils, the sodium hydroxide solution (lye), the recipe and the blender will be placed around the bowl.
In the mixing bowl, pour the heated oils over which you slowly pour the hydroxide solution, both at 35-50°C.
Immerse the blender, taking care not to introduce too many air bubbles in the composition, and mix. The mixture will begin to become milky opaque, once the oils and sodium hydroxide have begun to emulsify. Continue to mix with the blender and possibly, alternately with a spatula until the composition reaches the consistency of a fine, soft pudding.
The moment you can draw lines with the blender on the surface of the mixture, and they keep their shape for a while, you have reached the "trace" phase. Depending on the oils and additives used, this can happen after 5-15 minutes of mixing. Various substances such as essential oils or fragrance oils, clays or waxes can accelerate the production of "trace", the water discount as well. Some additives are added in different stages of "trace" for this very reason, they can thicken the composition a lot, and pouring it into shapes is more difficult.
Once you have reached the desired level of consistency, you can proceed to pour the composition into molds. For molds with patterns, the composition should be more fluid, and if you want to make patterns on the surface of the soap, it should have a thicker consistency.
Spray the surface of the soap with alcohol to limit the formation of sodium carbonate (the caustic soda reacts with the CO2 from the atmosphere and a thin, white layer appears on the surface of the soap).
After pouring into molds, the soap is placed in a clean and dust-free place and left to cool and solidify. This can take between 1-3 days depending on the recipe. If the soap is still soft to the touch, it can be left in the mold for a few more days or it can be put in the refrigerator to harden.
After the soap has hardened, remove from the molds and cut, if necessary, with a knife or special soap cutting equipment.
After hardening, the soap can be removed from the mold and cut as needed. You can use kitchen knives or special soap cutters. The cut soaps can be "cosmeticized" with a vegetable peeler, to have a more finished look.
Soaps are cured in clean, dust-free spaces, preferably on shelves or in crates, having enough space between them so that air can circulate freely and facilitate their drying. If you do not have spaces specially designed for soap curing, they can be stored in boxes and covered with paper towels so that no dust settles on their surface.
The soaps are left to cure for at least 4 weeks. The best results are obtained after 6 months. Do not use soaps that are not cured, as the composition of the soap is still reactive and, in contact with water, may cause skin irritations.
If you want the soap to go through the gel phase, immediately after pouring into molds, while it is still hot, you can cover or wrap it with foil, kitchen towels or blankets (insulate it).
You can choose one of two options:
a) after finishing, put the dishes and utensils in the sink and wash them with hot water and dishwashing detergent. Keep wearing gloves for this stage as well, because the soap composition is still reactive. Clean the dishes with paper towels, to remove as much of the oily substances as possible, making it easier to wash them.
b) some soap manufacturers prefer to place all used containers and utensils in a household bag after the preparation is completed, and allow the soap composition to harden on them.
The next day, remove the solidified soap from the dishes and wash them regularly with water and detergent.
Soap – product obtained by saponification of fatty acids or fats with solutions containing sodium or potassium hydroxide, and which together with water is used for cleaning.
Saponification – reaction by which a fat (vegetable or animal) in combination with a strongly alkaline substance: sodium hydroxide (NaOH) or potassium hydroxide (KOH) forms glycerin (a humectant) and a salt of fatty acids, called "soap". When sodium hydroxide is used, a solid soap is obtained. The use of potassium hydroxide results in a liquid soap. Only through this process can the "real" or "traditional" soap be obtained. During the saponification process, the soap composition will heat up, even if you use a cold process or work with substances at room temperature. The working temperature of the sodium hydroxide solution and oils used in the manufacture of soaps is between 35-50°C. It is preferable that the two substances to be at approximately the same temperature before mixing. You can also work with solutions and oils at room temperature, but the saponification process will take longer, more mixing will be needed.
Exothermic reaction – chemical reaction that produces a release of heat. Whenever working with caustic soda, it will be dissolved in water, not the other way around. Never put water over sodium hydroxide as it will cause a violent reaction.
Water bath – "bain marie", a vessel filled with water that is boiled, used to melt or slightly heat various products, such as oils used in the production of soap, without them coming into direct contact with the heat source.
Syndet – the word comes from the combination of the terms “synthetic” and “detergent”, and these are products that contain synthetic ingredients and result from the mixing of surfactants or detergents derived from oils, fats or petroleum products that are refined by many chemical processes other than traditional saponification.
Superfat – is a term used in the manufacture of cold process soaps, which refers to the amount of fat left free after the end of the saponification process. It is specifically calculated in the formulation of a recipe and is expressed as a percentage. Basically, it is about reducing the amount of soda needed to saponify the entire amount of oil used in the recipe, usually between 1-10%. By keeping an amount of unsaponified oils, the soap will be more moisturizing. It is also practiced if the recipe contains a high amount of vegetable butters that are solid at room temperature, to prevent the formation of a too strong or crumbly soap.
Water discount – reducing the amount of water used in the recipe, usually by 5-15%, to accelerate the production of "trace", hardening of the soap and its faster removal from the form.
Trace – term used to describe the time when the composition begins to thicken and has the texture of a pudding. It is the result of emulsifying the fats with the sodium (or potassium) hydroxide solution and can be of 3 types depending on how thick the composition is: light, medium or thick. Depending on how much the composition is mixed with the blender, different trace levels can be reached, the more it is emulsified, the thicker the composition will be. Once the right level of trace has been reached, the prepared soap can be transferred into molds. It is left to rest for 1-2 days depending on the recipe, during which time it will harden. After the soap has hardened, it can be cut, in the case of soaps poured in "block" shapes, or they can be removed from the molds and left to cure.
Gelling – stage through which the final composition of the soap passes, after insulation, and has the effect of changing the appearance of the product. It becomes more translucent in some regions or on its entire surface. This stage can be influenced by the temperature at which the soap is stored after it is poured into molds, or by the amount of sugars present or added to the composition. This process only aesthetically influences the finished product. Soaps that have not gone through the gelling phase remain duller, their quality not being affected by this aspect.
Emulsification – is defined as a process by which a liquid is dispersed into another immiscible liquid, by mechanical mixing. Good examples of emulsions are mayonnaise, creams (lotions) or homogenized milk.
Curing – process by which the prepared soap hardens. During this time the water contained in the soap will evaporate, forming a durable and long-lasting soap which will be gentler on the skin. Soap curing is usually done in rooms or places without moisture, on shelves or in crates that allow air circulation. The curing process lasts at least 1 month. The recommended period is 6 months, but can be extended to 12 months in the case of soft oil soaps. Freshly prepared soaps will not be used until they have been left to cure for at least 4 weeks. Some recipes produce soaps that have a soft consistency, even after they have been removed from the molds.
Caustic soda – or sodium hydroxide is a white crystalline substance, strongly alkaline (base), natural, in the form of flakes, pearls or powder, corrosive and hygroscopic (attracts water). It is soluble in water, and in contact with it produces an exothermic reaction (heat release). During the dissolution of caustic soda in water or other liquids, caustic vapors will form which should not be inhaled. Therefore, during the preparation of sodium hydroxide solutions (lye), work in a well-ventilated room. If this possibility does not exist, prepare the solution under a kitchen hood.
Distilled water –also called demineralised water, is the water from which the impurities were removed by the distillation process, which involves boiling water (vaporization) and then condensing the vapors obtained in another container. Other production processes also include deionization and reverse osmosis. It is chemically pure water. When preparing sodium hydroxide solutions it is necessary to use distilled water, because caustic soda can interact with impurities contained in ordinary tap water.
Insulation – process that prevents the cooling of the soap composition and encourages its entry into the gelling phase. This involves covering the mold in which the soap is poured with different materials to maintain a high temperature for a period of time. It is not a mandatory step in soap making, some manufacturers choose to let the soap cool to room temperature. If the temperature is not uniform throughout the composition, after the soap has hardened and can be removed from the shape or cut, the color or texture may be different in the areas where the gelling has occurred. Product quality is not affected. The insulation time differs depending on the ambient temperature and the recipe, and care must be taken that the soap does not overheat, resulting in cracks or eruption of the composition, and its flow from the mold.
Lye calculator – tool used to calculate the required proportions of ingredients to be added to the recipe. There are many online calculators that also provide information on the properties of the chosen oils, the recommended amount of fragrance/essential oil but also options to reduce the amount of water used, or increase the amount of oil left free after saponification (superfat). These calculators are based on the saponification value specific to each oil/butter, and display the amount of sodium hydroxide and water needed to prepare a certain amount of soap chosen by the user.
Oils and butters (vegetable fats) – are a mixture of triglycerides, can be extracted from the seeds or fruits of various plants, and form soap in reaction with sodium/potassium hydroxide. The best soaps result from the combination of different types of oil, but there is also soap obtained from a single oil: Castile or Marseille soap - made only from olive oil. Most oils are not recommended to be used in the maximum percentage because the soaps obtained can be too soft (in the case of fluid oils) or too hard (in the case of butter), so the combinations of oils and butters are the most successful, especially when taking into account and the properties of each.
Saponification value – how many grams of sodium or potassium hydroxide are needed to completely saponify 1 gram of fat (oil or butter). Each oil or butter has its specific saponification value, for example, extra virgin olive oil has a saponification value of 0.185, which means that 0.185 g of NaOH is needed to saponify 1 g of oil.
This formula was developed by Elemental's qualified staff. The recipes are intended to exemplify the use of products marketed by Elemental and are believed to be accurate, however, Elemental assumes no liability or risk associated with the use of its products for the preparation and evaluation of the recipe as the conditions of preparation and use are beyond its control. The Elemental customer must ensure that the reproduction of the formulation does not infringe any intellectual property rights and that it complies with the specific rules and regulations in force. The person who prepares the recipe must refer to the safety data sheets to ensure the safe handling of all raw materials and bears full responsibility for ensuring the safe and correct use and storage of all materials procured and used. Assessments of the safety, stability, regulatory compliance and suitability of this recipe, methods and the finished product are the sole responsibility of the user and/or the legal entity placing the product on the market. Elemental is not liable for any damages resulting from the use of this information, and assumes no responsibility for misuse of selected materials, formula or method, in whole or in part.