2. Mixing the soap liquid

In the second step, the cleaned oil is mixed with more liquid soda and stirred thoroughly. The correct mixing ratio is crucial: for every 2 liters of cleaned oil, exactly 1 liter of soda must be added. If this step is not done carefully, the entire process can fail – if the soda concentration is too low, the soap won’t clean effectively; if it is too high, the soap can become toxic and harmful to users. That is why a device called a hydrometer is used to check the exact concentration level.