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2 - Using caustic soda: safety precautions

0 - Why and how to make your own soap?
1 - How: the saponification process
2 - Using caustic soda: safety precautions


Using caustic soda: safety precautions
Sodium hydroxide is very corrosive; its pH varies between 12 and 14 (FYI, water has a pH of 7, skin around 6, and hair around 5).

Making soap requires you to mix caustic soda with water (or another liquid, for example, herb tea), which will significantly increase the liquid temperature. To avoid dangerous splashes, it's very important to POUR THE CAUSTIC SODA INTO THE WATER (not the water into the soda), and this lye mixture into the oil.
Pouring water into caustic soda would provoke a "volcano effect". The same thing will happen at this point if you use objects made of materials that react with lye e.g. metals (except stainless steel) and wood. Using glass containers and a stainless steel spoon to stir is a good solution.

And you don't want the volcano effect to happen because:
             
Caustic soda is irritating and corrosive to skin, eyes, respiratory and digestive tracts.

Knowing that, here are a few recommendations that are important to follow:

  • Be sure to have time and to be alone for at least 2 hours. Keep children, husbands, and animals away.
  • Cover yourself: it's very important to use gloves, preferably a long-sleeved top and safety glasses. You should also use gloves to unmold and cut the finished soap.
  •  Cover your workspace (old newspapers). 
  •  Use an electronic scale; a kitchen scale with 1g precision is fine if you make batches of over 400 g of oil.
  •  Do not breathe lye emanation when mixing water and lye; you should use a mask, and/or work in a well-ventilated area.
  •  You will use a hand blender to mix the oil and water solution. It’s pretty obvious but does not lift the blender while it’s turned on.
  •  The utensils and containers you use for soap making are from then on strictly reserved for soap making: you must never use them again for cooking (risk of food poisoning).
  • The process of saponification requires a precise quantity of lye; this quantity varies depending on the oil(s) you use. So always use a lye calculator, even if you reuse a recipe seen on the internet (check twice!) (read more on lye calculators). 
  • Wait at least 4 weeks (we call it the cure time) before using your newly made soap and test its pH. It should not be higher than 10. Use pH paper strips or do the "tongue test": touch the tip of your tongue to a fresh bar of soap. If no electric zing, it is safe to use. 

  • Finally, if you really want to make soap, read this article entirely and also some others before you start.
 
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