Introduction: Zero Waste Project: Eco-friendly Handmade Soap Making With Kids From Used Cooking Oil

About: Happy Sagi~


Let's enjoy the soap-making journey together with kids! The most effective way would be to involve the children in raising environmental awareness by conducting them some awareness-raising activities. This eco-friendly soap making activity not only elevate environmental awareness but also instil good personal hygiene in children such as inculcating hand washing habits.

How to recycle waste cooking oil and turn into eco-friendly soap?

The soap making process is environmentally-friendly and cost-effective. Recycling used cooking oil into homemade soap is a great way to create less waste as it utilizes used cooking oil as its raw material. Making a batch of lye soap takes 1-2 hours initially and then an additional 4-6 weeks before your family members should use or gift it.

Fun and interesting science experiments for kids.

With a few simple safety precautions, making soap can be a fun and efficient way to understand chemical reaction between water and sodium hydroxide (lye). Proper ventilation, along with gloves/eye protection will increase your level of safety in soap making process. Do your research before you begin this awareness-raising activity with kids. Always read the soap making recipes carefully, and enjoy!

Step 1: Tools & Ingredients:


Stainless Steel Pot,

Measuring Cup



Cooking Thermometer

Digital Scale

Mould (soap mould or any recycled mould such as yogurt cup or milk container is also applicable).


1kg Used Cooking Oil

150g Sodium Hydroxide (Lye)

280ml Water

Color or Scent/Essential oil (optional)


Sodium Hydroxide (lye) must be handled with care. You and kids should wear glove or other protection before activity start. The whole process must be done in a ventilated place.

Step 2: ​Cover Work Area With Old Newspaper.

Cover your work area with newspaper, then carefully fold up and seal the used newspaper in a trash bag when you are done working.

Step 3: ​Filter the Used Cooking Oil and Weight 1kg Into a Stainless Steel Pot.

After using cooking oil for frying food, you may have leftover dark, so you can reuse that oil to DIY Eco-friendly soap, as long as you filter it out.

Step 4: Measure 280ml of Water.

Step 5: Wear Glove. Weight 150g of Lye and Add Slowly Into Water.


a. Make soap near a water source so you can flush the affected area if needed.

b. Handle a lye carefully with a protective gloves.

c. The chemical reaction will heat up the lye solution.

d. Be cautious that the water temperature may increase drastically during this steps (around 80°C).

e. Cover the steam with newspaper for 2 minutes then start stiring.

Step 6: Stir the Lye Solution in a Well Ventilated Place Until Clear Mixture.

Step 7: Prepare Thermometer and Wait the Mixture Cool Down to 50°C - 45°C.

Step 8: Add 1kg Used Cooking Oil Into a Stainless Steel Pot.

Step 9: Pour the Lye Solution Carefully Into the Oil and Keep Stiring Until “tracing” Occur.

Step 10: Add Few Drops Color or Scent/essential Oil If Desired and Continue Stirring.

Step 11: Pour the Soup Mixture Into Moulds Quickly When It Become Thicker Texture.

When soup mixture become thicker, pour it into the mould quickly (any recycled mould such as yogurt cup/milk container is also applicable).

Step 12: Please Remove the Solidified Soap Carefully After 48 Hours.

Remove the solidified soap from the mould carefully after 2 to 3 days and let it air dry (avoid too much direct sunlight).

Step 13: Homemade Soaps Are Ready to Use After 4 Weeks.

Making eco-friendly soap with kids is fun and easy. The soaps will turn hard. They are ready to use after 4 to 6 weeks. Hand washing is one simple solution that children can learn to protect themselves against infectious diseases. This activity not only turn over waste oil to increase awareness and implement a zero-waste but also inculcate children hand-washing habits in a fun and engaging way!

Step 14: Safety Guide & Summary of Soap Making Process.

Soap Making Process:

1.Select a deeper & heat-proof containers to contain all the water, oils, and lye while avoiding spills & splashes.

2. Never add water to the lye and always add add lye slowly to water and wear protective clothing/gloves.

3. Mixing lye solution creates fumes which should not be inhaled. An exothermic reaction that causes a dramatic temperature increase in this step.

4. The working area should have good ventilation to avoid breathing in lye fumes.

5. Carefully pour the lye solution into the oil.

6. Lye can burn the skin and damage the eyes in the dry or wet form. As a result, please wash your hands and arms when you are done making soap.


1. Store lye appropriately. Always be kept out of reach of children and should be properly labeled to ensure nobody touches or tampers with it.

2. Placing the soap bars in a cool & dry location with plenty of air flow for 4 weeks or longer.

3. The handmade soap can last months to years, it depends on proper storage.

4. Airflow is key to avoiding rancidity. Don't enclose soap in an airtight container or covering for storage.

Safety Tips:

1. Vinegar will counteract lye and stop its burning.

2. In case the lye gets on the skin, flush it with lots of water with some salt if there is no vinegar.

3. Milk will neutralize lye and can be used if the lye is accidentally swallowed.

4. Do not give vinegar or induce vomiting to someone who has swallowed lye.

5. If either of these thing happen, get medical help and call emergency line immediately.

The lye soap has to be aged to allow the fat in the soap to mellow the lye. Therefore, the eco-friendly homemade soap will not be harsh to the skin!

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