Caustic Soda and Soda Crystals

What’s the Difference Between Caustic Soda and Soda Crystals?

Caustic soda and soda crystals can both be used for household cleaning. However, while they have similar names and are great for cleaning, they’re not the same substance. In fact, both are vastly different compounds that you must be careful not to muddle up.

But what’s the difference between caustic soda and soda crystals? Aside from the name, are there any similarities between these two substances? And which is the best option for cleaning specific surfaces around the home?

In this article, we run through the main differences between caustic soda and soda crystals, including their chemical structure, strength, cleaning uses, safety considerations, and where to buy each product.

We also help you choose the most appropriate option for your cleaning needs. Keep reading for all you need to know!


The Difference Between Caustic Soda vs. Soda Crystals

Caustic Soda vs. Soda Crystals

Despite both caustic soda and soda crystals having “soda” in the name, the two are incredibly different in many ways. Below are the key differences to be aware of.

1. Chemical structure

Caustic soda (also known as lye) is chemically referred to as sodium hydroxide with the formula NaOH. It is made from sodium ions (Na+) and hydroxide ions (OH-).

On the other hand, soda crystals (also known as washing soda) have the chemical name sodium carbonate and the formula Na₂CO₃. It’s made from sodium ions (Na+) and carbonate ions (CO₃-).

Both compounds are alkaline, and the “soda” part in the names of both substances comes from the sodium ions (Na+) that make up part of their chemical formulas.

However, the OH and CO₃ ions that make the remaining part of each compound are entirely different.


2. Appearance

Both caustic soda and soda crystals are white in colour, but the texture is slightly different. Soda crystals have a finer and more powdery consistency and look a little like yeast. On the other hand, caustic soda most commonly comes as larger white flakes.

That said, sodium hydroxide (caustic soda) is also available to purchase as “micro-pearls”—tiny white spheres with a more powder-like appearance. They look a bit like fish eggs or caviar.

Pearls are more expensive than flakes and are typically used in large-scale industrial settings only, such as in the production of petrol, paper bleaching, and chemical processing of cotton.

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2. Strength and abrasiveness

Both caustic soda and soda crystals are abrasive substances that make them useful for cleaning. However, the strength of the chemicals varies dramatically.

Whereas soda crystals are only mildly abrasive due to their alkaline nature, caustic soda is extremely powerful and a highly corrosive product. If handled incorrectly, it can cause chemical burns to the skin.

The overall strength of the cleaning product also depends on how diluted the chemicals are.

You should always dilute both caustic soda and soda crystals before using them for cleaning. The more water you add, the lower the strength of the cleaning solution.


3. Cleaning uses

Because of its corrosive nature, caustic soda can easily damage surfaces around your home. In fact, it only has one real cleaning use: unblocking drains and pipes.

Mix 100g of caustic soda with a litre of water and pour it down the clogged drains. It will corrode and remove the blockage within 30 minutes.

So, what can soda crystals be used for? As they’re not corrosive, soda crystals have much more wide-ranging uses around the home.

They’re mildly alkaline and abrasive and are great at eliminating oily residues, mould and mildew, and hard-to-remove organic stains like blood and coffee.

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In fact, you can use soda crystals for cleaning all the following things and more:

  • Greasy extractor fans
  • Ovens and oven racks
  • Burned pots and pans
  • Stained grout and tiles
  • Algae-stained decks and patios
  • Mouldy washing machines
  • Stained items of clothing


4. Where to buy in the UK

Soda crystals are one of the most common DIY cleaning products in the United Kingdom.

You can purchase soda crystals in almost all supermarkets, such as Tesco, Sainsbury’s and Morrisons, or at online marketplaces, such as Amazon.

On the other hand, caustic soda is a semi-restricted product and can be difficult to source in the UK as it can be used to manufacture illegal drugs and is very dangerous when used in large quantities.

If you want to buy caustic soda, your best option is to purchase cleaning products that contain caustic soda rather than the product itself. These can be found at shops like B&Q or online.

woman wearing cleaning gloves


5. Safety considerations

Soda crystals can act as a mild irritant but are generally safe to use without significant safety considerations.

However, you should wear rubber gloves when cleaning with strong concentrations and wash any residue from your hands or eyes as quickly as possible.

Comparatively, caustic soda is a very corrosive chemical and can be extremely dangerous if not handled with care.

You should ideally wear protective clothing (gloves, apron, etc.), a face shield, and safety goggles when handling the product.

If you get any on your skin, rinse immediately with water to reduce the severity of chemical burns.

The main dangers of using caustic soda arise when using the pure product directly, which is uncommon in the UK due to its semi-restricted status.

However, while commercial cleaners that contain caustic soda will be diluted, appropriate care should still be taken.


Soda Crystals or Caustic Soda – Which Is Best?

Soda Crystals or Caustic Soda

Caustic soda is the top option for unblocking pipes and drains. Its strong corrosive properties mean it effortlessly unclogs even the worst blockages.

If you’re dealing with stubborn blockages, a strong drain unblocker like this one available on Amazon, containing sodium hydroxide, is an excellent option when handled with care.

While caustic soda is more powerful, soda crystals can also effectively remove “normal” blockages while also being safe and more accessible.

Simply pour boiling water down your drain, followed by a cup of soda crystals, followed by more boiling water. After five minutes, the blockage should be cleared. Alternatively, try this drain-cleaning method that combines using soda crystals and vinegar.

Soda crystals are almost always your best option for cleaning other surfaces, too. They’re incredibly versatile, available in most UK supermarkets, and are much safer to use.

You can use them to clean everything from stains on your carpets and clothes to your greasy oven, dirty garden patio, or even your washing machine.