In our daily lives, cooking oil is an indispensable resource, but we often don't know what to do with it once we've used it. Improper disposal of oil can cause major environmental problems, such as water and soil pollution, as well as damaging sewage systems. However, there is a creative and eco-friendly solution to reuse it: making homemade soap! In this article, you'll learn step by step how to turn used oil into a natural, effective and environmentally friendly soap.
Why make soap from used oil?
Before we get into the details of the soap making process, it is important to understand the benefits of using used oil as the main ingredient.
Environmental protection: Oil poured down the drain ends up in rivers, lakes and seas, causing serious damage to aquatic fauna. By recycling used oil, we reduce pollution.
Money saving: Making your own soap from recycled ingredients is cheaper than buying commercial soaps. You can also reuse bottles and containers to store soap.
More natural soap: Homemade soaps are free of many of the chemicals and additives found in industrial products. If you add natural ingredients such as essential oils, you will have a healthier product for your skin.
Creative and educational activity: Making soap is a great activity to share with your family, especially to teach about sustainability and the importance of recycling.
Ingredients and materials
To make soap from used oil, you'll need a few basic ingredients and tools. These are easy to find and you probably already have them at home.
Ingredients:
Used oil: Preferably olive or sunflower oil, although you can also use other vegetable oils. Filter the used oil to remove any food residue.
Caustic soda (sodium hydroxide): This is the chemical agent that enables saponification, that is, the reaction that turns oil into soap. It can be purchased at cleaning supply stores or pharmacies. It is important to handle it carefully, as it can be dangerous if not used correctly.
Water: Used to dissolve caustic soda.
Essential oils (optional): If you want to add a touch of fragrance to your soap, you can add a few drops of essential oils such as lavender, tea tree or eucalyptus. In addition to smelling good, some of these oils have beneficial properties for the skin.
Natural colorants (optional): If you want your soap to have a specific color, you can add natural colorants such as turmeric (for yellow tones), cocoa (brown), or green clay (soft green).
Materials:
Gloves and protective glasses: Caustic soda is highly corrosive and can cause burns, so it is essential to protect yourself properly.
Plastic or stainless steel container: To mix the ingredients. Do not use aluminum containers, as they react with the caustic soda.
Wooden or sturdy plastic spoon: To stir the mixture.
Silicone or plastic molds: These can be baking molds or recycled containers.
Hand mixer: It will facilitate the emulsification process.
Kitchen thermometer: To measure the temperature of the mixture.
Newspaper or cardboard: To protect work surfaces.
Steps to make soap with used oil
Below I explain the detailed process for making homemade soap using recycled oil. This method is simple, but requires patience and caution.
1. Preparing the workspace
Before you begin, make sure the area you're going to work in is well ventilated, as caustic soda releases fumes that can be irritating. Protect the surface with newspaper and have all the tools and materials you're going to use at hand. Don't forget to wear gloves and protective glasses throughout the process.
2. Filter the used oil
For good quality soap, it is important that the oil is clean. If you have used the oil for frying, it is likely to contain food residue. Strain it through a fine strainer or cloth to remove all impurities. Once filtered, the oil is ready to be used.
3. Prepare the mixture of caustic soda and water
This is the most delicate step, as caustic soda is dangerous if not handled correctly. Slowly add the caustic soda to the water (never the other way around) and stir carefully. You will see that the temperature of the mixture increases rapidly. It is important that you do this in a ventilated place and avoid inhaling the vapours. Allow the mixture to cool until it reaches about 40-50°C.
4. Mix the oil with the caustic soda
Once the caustic soda mixture is at a suitable temperature, slightly heat the used oil until it is also at about 40-50°C. It is important that both mixtures are at the same temperature for the saponification process to occur efficiently.
Pour the lye mixture into the used oil slowly, while stirring with a wooden spoon or hand mixer. Continue stirring until the mixture becomes smooth and thick, similar to a puree. This process can take between 15 and 30 minutes, depending on the amount of soap you are making.
5. Add essential oils and colorants (optional)
Once the mixture has reached the desired consistency, you can add essential oils and natural colorants if you wish. Add a few drops of essential oil and continue stirring to distribute the scent evenly. As for the colorants, add them in small amounts until you achieve the shade you prefer.
6. Pour the mixture into the molds
When the mixture is ready, carefully pour it into the molds. Tap the molds lightly against the table to remove any air bubbles. Once you have filled the molds, cover the top with a towel or paper to keep the heat in, which will help complete the saponification process.
7. Let the soap rest
Leave the molds in a dry place at room temperature for 24 to 48 hours. After this time, the soap will have hardened enough to be removed from the mold. If the soap is not solid enough, let it sit a little longer.
8. Cut and cure the soap
Once unmolded, cut the soap into portions if necessary. However, it is not yet ready for immediate use. The soap needs a curing time, which is usually 4 to 6 weeks. During this period, the caustic soda is completely neutralized and the soap acquires its final consistency. Place the soap bars in a cool, dry place, turning them over from time to time so that they cure evenly.
Additional Tips for Soap Making
Customize your soap: You can experiment with different essential oils, dried herbs, or natural exfoliants like oatmeal or coffee grounds to create unique soaps.
Storage: Store the soap in a cool, dry place. If you want to give it as a gift, you can wrap it in kraft paper or eco-friendly cloth bags.
Recycle your molds: Use recycled containers such as cut plastic bottles or yogurt containers to shape your soap.
Caution with caustic soda: Always handle caustic soda with great care, following all necessary safety measures.
Homemade soap has several advantages over commercial soaps. By making it yourself, you can control the ingredients and avoid harsh chemicals like sulfates and parabens, which are often present in industrial products. Additionally, homemade soap is gentler and kinder to the skin, making it a great choice for people with sensitive skin or allergies.
Finally, by reusing used oil, you are helping to reduce the environmental impact, transforming waste into a useful, quality product.