Caustic soda, whose chemical compound name is NaOH (sodium hydroxide), is a strong alkali. Its pH can reach 14 in a 50% concentration solution. Do not let caustic soda get on your skin, especially your eyes.

It can damage glass, plastic, rubber, iron, copper, and aluminum. Avoid using a nonstick pot, because it is made of aluminum alloy under the surface coating, which is very risky if the coating has been scratched. Please choose suitable containers such as PP (polypropylene), HDPE (high-density polyethylene), or stainless steel.

Must wear safety goggles — even swimming goggles are better than nothing. If it accidentally touches your skin or eyes, immediately rinse with warm running water for 20–30 minutes and seek medical advice.

Of course, it is also better to wear gloves. I usually wear vinyl or latex gloves, which are easy to buy in supermarkets. Any waterproof glove will do the job. However, I would say goggles are a must-have item — even more important than gloves.

A strong exothermic reaction occurs when caustic soda contacts water — in other words, it releases a lot of heat. Imagine adding a small amount of water to caustic soda: the heat will instantly boil the water and cause dangerous splashing. This is the worst-case scenario we want to avoid.

The correct way is Adding caustic soda into water. A pot of water can absorb the heat; you may see some steam, but it is safe as long as you only add a spoonful of caustic soda at a time. Since you don’t want to breathe in the steam, I recommend doing this process in a well-ventilated place, such as a balcony.

For your family’s safety, especially if you are processing soap in the kitchen, I suggest letting everyone at home know that soap making is in progress. Also, use caustic soda only when needed and do not leave it unattended on the worktop or table.

Using caustic soda is the trickiest step in soap making. However, with the knowledge above, you can do it safely and successfully.