Caustic Soda, Lye and Sodium Hydroxide

Wanting to use Caustic Soda, Lye or Sodium Hydroxide? But you don’t even know where to start? Like what’s with all the different names? Yes, we know it can be a little overwhelming but we are here to help break it down easier for you.

Caustic soda is sodium hydroxide which is lye - they are the exact same thing; just different names. The reason behind the different names is mainly to do with the chemical name being “sodium hydrate” and the chemical itself is “caustic or corrosive”, leading to being known as caustic soda. When it comes to the term “lye” it is a common name that relates to sodium hydroxide in the solution to make soap.


The nature of caustic soda is usually of a white powder consistency that is either in the form of flake, crystals or pearls, our caustic soda is normally pearls. The different types of forms do not change the outcome of what you are trying to do. Caustic soda can be used in a variety of applications such as soap making, frosting glass, unblocking drains, candle making and chemical experiments.


The reason caustic soda is great for unblocking drains and making soap is mainly because the caustic reacts with fat. This means that it changes the composition allowing it to dissolve the fats (in the sink or soap formula) to make soap consistency and this process is called saponification.


It is important to understand the reaction caustic soda has with water. Caustic soda is exothermic, which means that they generate heat and give off hydrogen. When you add hot water to caustic soda this process can be quite dangerous as it can cause an explosion of alkali where acid can be distributed all over the place. Instead use cold water, even though the process may take longer, it is far safer as the caustic soda is exothermic which means the hot water isn’t necessary (but is still dangerous, so handle with care).


If you have any questions, leave a comment below or send us an email we are happy to help.

All information provided is based on research. Merely recommendations.

Potassium Hydroxide 4KG

Potassium Hydroxide 4KG


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Potassium Hydroxide 17kg

Potassium Hydroxide 17kg


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Comments (2)

Hot caustic bath

By: on 25 November 2021
I'm building a hot caustic bath for cleaning mechanical parts. Which one do I need? Thanks

Sydney Solvents Response
Hello, Our Caustic Soda in powder form will be best. Please be careful when adding the powder to liquid as there can be a reaction.

instruction for cleaning/unblocking drain

By: on 7 January 2020
Hi, I bouth 5kg of caustic soda and was wondering if you could provide an instruction on how to use caustic soda to clean/unblock pipes, eg. dillution required, etc... thanks, Eric

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