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What is washing soda ? It’ often labelled sodium carbonate (Na₂CO₃) on packaging — is a highly alkaline, white crystalline powder widely used as a heavy-duty cleaning agent and laundry booster in homes across the UK. It’s the decahydrate form of sodium carbonate, which dissolves in water to form a strongly basic solution that cuts through grease, neutralises acids and lifts stubborn soils.
This powerful cleaner goes beyond everyday detergents. In laundry rooms, it softens hard water, boosts detergent performance and breaks down tough stains that ordinary wash powders struggle with — especially on cotton whites like white socks.
Sodium Carbonate — The Chemistry Behind Washing Soda
“Sodium carbonate” and “washing soda” are chemically the same thing, just different names reflecting context: scientific (sodium carbonate) vs cleaning (washing soda/soda crystals). The term soda ash is also used interchangeably in industrial or manufacturing contexts. When sodium carbonate dissolves in water it creates an alkaline solution with a pH often around 11 — much stronger than baking soda — which makes it excellent for tackling grease and oily residues.
This high pH also explains why washing soda can soften hard water: it reacts with calcium and magnesium ions that make water “hard”, allowing detergents to work more efficiently.
Soda Crystals Uses for Cleaning & Laundry
Using washing soda in its granulated form — commonly known as soda crystals — unlocks a range of practical cleaning tasks throughout the home:
1. Boosting Detergent in Laundry
When added to the wash, soda crystals help detergents penetrate fibres and lift stubborn stains like oil, grass or sweat from clothing. They’re especially useful in areas with hard water where detergents alone may under-perform.
2. Pre-Soaking Tough Stains
Dissolving a few spoonfuls of washing soda in hot water creates a soak solution that loosens dried-in soils before the main wash — ideal for whitening clothes like white socks or deeply set food stains.
3. General Surface De-Greasing
A warm soda crystals solution will cut through kitchen grease on tiles, splashbacks and cooker hoods. It’s also effective on textured grout where oils can hide.
4. Washing Machine & Drain Maintenance
Soda crystals help dislodge detergent build-up inside washing machines and can be used to unclog slow drains when mixed with hot water.
5. Removing Soap Scum & Hard Water Marks
Their alkaline nature dissolves soap residue and mineral deposits left from hard water on showers and taps.
Washing Soda for Laundry — How to Use
Washing soda works in multiple laundry roles:
- Water softener — add a tablespoon to each wash load to combat hard water.
- Detergent booster — combine with your regular detergent to enhance cleaning power.
- Pre-treat soak — dissolve in hot water, soak stained garments, then wash.
Because washing soda is more alkaline than detergent and baking soda, it should be used sparingly on delicate fabrics and always dissolved thoroughly before adding clothes.
Baking Soda vs Soda Crystals — What’s the Difference?
Baking soda (sodium bicarbonate) and washing soda (sodium carbonate) both appear as white powders but behave differently:
- Baking soda is mildly alkaline (pH around 8.4) and ideal for gentle deodorising, baking and light scouring.
- Washing soda/soda crystals are strongly alkaline (around pH 11), making them better suited to heavy-duty cleaning and laundry boosting.
They are not interchangeable in recipes: washing soda’s stronger alkalinity can damage delicate fabrics and surfaces if used where baking soda would suffice.
Is Borax the Same as Washing Soda?
No — while both are used in cleaning, borax (sodium borate) is a different compound. It has its own set of cleaning properties, including fungicidal activity, but does not soften water or break down soils in the same way as washing soda. Never substitute borax directly for washing soda without checking instructions for the task at hand.
What Is Washing Soda Called in the UK?
In UK shops and cleaning guides, you’ll see washing soda labelled as:
- Soda Crystals
- Washing Soda
- Sodium Carbonate
- Soda Ash (less common on consumer packaging)
These terms all refer to the same versatile cleaning ingredient used for laundry and household cleaning.
Where Can I Buy Washing Soda or Soda Crystals in the UK?
Washing soda (soda crystals/sodium carbonate) is widely available in the UK:
- Supermarkets (household aisles)
- Hardware stores and DIY centres
- Online marketplaces (e.g., Amazon UK)
- Eco cleaning specialist shops
Look for soda crystals or washing soda on the label in the laundry or cleaning sections.
Sodium Carbonate pH & Safety Notes
Washing soda dissolves to form a strongly alkaline solution (high pH), which is why it’s such a good cleaner but also why it can irritate skin and eyes if used undiluted. When handling soda crystals:
- Wear gloves
- Avoid inhaling dust
- Store dry away from children and pets
This alkalinity is what breaks down greasy soils and neutralises acids — but always respect the strength of the product when cleaning.
Sodium carbonate hydrochloric acid
When sodium carbonate encounters hydrochloric acid, a fascinating neutralization reaction occurs that demonstrates the practical chemistry behind everyday cleaning. The carbonate ions actively capture hydrogen ions from the acid, producing three distinct products: sodium chloride (table salt), water, and carbon dioxide gas.
This chemical interaction proves particularly useful for people working with cleaning solutions. The effervescent bubbles of CO₂ gas help lift stubborn dirt from surfaces, making this reaction valuable in specialized cleaning methods. For instance, when treating tea stains from ceramics, the gentle fizzing action can help dislodge discoloration without harsh scrubbing.
The reaction follows a predictable two-stage process, where sodium bicarbonate forms as an intermediate before converting to the final products. Understanding this mechanism helps explain why mixing carbonate-based cleaners with acidic substances creates that characteristic bubbling effect.
Common Misuses to Avoid
- Do not use washing soda on aluminium or delicate fabrics as high alkalinity can etch metals and degrade fibres.
- Avoid mixing with strong acids — the reaction can release heat or harmful fumes.
- Do not ingest — unlike baking soda, washing soda is not food safe.
Frequently Asked Questions
Is washing soda the same as baking soda?
No. Washing soda (sodium carbonate) is much more alkaline and powerful than baking soda (sodium bicarbonate). Baking soda is gentle and food-safe, while washing soda is a heavy-duty cleaner.
Is borax the same as washing soda?
No. Borax is sodium borate — a different compound with different cleaning actions. It does not soften water or act the same way as washing soda.
What is washing soda called in the UK?
In the UK it’s commonly sold as soda crystals or washing soda — both names refer to sodium carbonate used for cleaning and laundry.
What is a substitute for washing soda?
Baking soda can be used for cleaning. For heavy limescale or mineral build-up, specialized descalers are better suited since washing soda’s alkalinity isn’t ideal on sensitive surfaces.
What is washing soda?
Washing soda is the cleaning name for sodium carbonate — a highly alkaline powder used to soften water, boost detergents and cut through grease and stains in laundry and around the home.
Where can I buy washing soda or soda crystals in the UK?
You can find soda crystals in the laundry aisle of UK supermarkets, DIY stores, and online retailers — look for “washing soda” or “sodium carbonate” on the label.
