Eco Cleaning Guide
DIY Natural Laundry Detergent with Sodium Carbonate (Soda Ash)
Powerful, eco-friendly, and cheaper per load than anything from the supermarket shelf. Four ingredients. Twenty minutes to make. Enough for 40–50 loads per batch.
Commercial laundry detergents are packed with synthetic surfactants, optical brighteners, artificial fragrances, and petroleum-derived compounds that linger in waterways long after they go down the drain. Sodium carbonate — one of the most effective, biodegradable, and affordable cleaning minerals available — is the backbone of traditional washing powders and forms the heart of any genuinely effective homemade detergent. Here is everything you need to make your own, understand why it works, and get the best results from every wash.
What Is Sodium Carbonate (Soda Ash)?
Sodium carbonate (Na₂CO₃) is a naturally occurring alkaline mineral salt also known as soda ash or washing soda. It has been used in cleaning and soap making for thousands of years — the ancient Egyptians used naturally occurring natron (a mixture of sodium carbonate and sodium bicarbonate) for cleaning, preservation, and ritual purposes.
Today sodium carbonate is produced commercially via the Solvay process or sourced from natural trona ore deposits. It is classified as biodegradable, non-toxic in standard cleaning concentrations, and is approved for use in ECOCERT and Australian Certified Organic cleaning product formulations.
- Chemical formula: Na₂CO₃
- Also known as: Soda ash, washing soda, soda crystals
- pH in solution: Approximately 11 — strongly alkaline
- Appearance: White crystalline powder or granules
- Biodegradable: Yes — breaks down to sodium and carbonate ions in waterways
- ECOCERT approved: Yes — permitted in certified organic cleaning formulations
- Not the same as: Baking soda (sodium bicarbonate, pH ~8.3) or caustic soda (sodium hydroxide, pH ~14)
"Sodium carbonate has been cleaning clothes for over 4,000 years. It doesn't need petroleum chemistry to work — just water, alkalinity, and a surfactant alongside it."
The Science: Why Sodium Carbonate Cleans So Well
Understanding what each ingredient does helps you adapt the recipe for different needs — harder water, sensitive skin, heavily soiled loads, or specific fabric types.
How Sodium Carbonate Compares to Other Laundry Additives
The Recipe: Homemade Natural Laundry Powder
Homemade Natural Laundry Powder
HE & Top-Load Safe · Makes ~800g · 40–50 Loads- Sodium carbonate (soda ash)400g — 50%
- Baking soda (bicarbonate of soda)300g — 37.5%
- Natural soap bar, finely grated100g — 12.5%
- Essential oil (optional)20–40 drops
- Grate the soap bar using a box grater or food processor. Finer grating produces better results — aim for small flakes rather than shreds. Dry grated soap dissolves more easily in the wash.
- Combine sodium carbonate and baking soda in a large stainless steel or glass bowl. Mix well with a spoon or whisk to distribute evenly.
- Add grated soap flakes and mix thoroughly until evenly distributed throughout the dry powder. Break up any clumps with your fingers.
- If using essential oils, add drop by drop while stirring continuously to prevent localised clumping. Mix for 1–2 minutes after the last drop.
- Transfer to an airtight glass or BPA-free plastic container. Store in a cool, dry place away from moisture. A sealed container is important — sodium carbonate absorbs moisture from the air and can clump if exposed.
- Standard load15–20g (1 tbsp) per wash
- Heavily soiled load30g (2 tbsp) per wash
- HE front-loaderAdd directly to drum, not dispenser
- Cold washPre-dissolve in 200ml hot water first
Soap bar choice matters. A simple, unscented tallow or coconut oil soap bar produces the best cleaning results — the high saturated fat content makes it a more effective surfactant in alkaline conditions. If using a commercial soap bar, choose the simplest, most additive-free option available. Your own homemade CP soap (especially a high-coconut formula) works exceptionally well here.
Liquid Detergent Variation
Prefer a liquid detergent? The same formula can be made as a liquid concentrate — useful for cold washes (where powder may not fully dissolve) and for pre-treating stains directly on fabric.
Liquid Laundry Concentrate
Cold Wash Friendly · Makes ~2 Litres · 40–50 Loads- Boiling water2 litres
- Sodium carbonate (soda ash)150g
- Baking soda (bicarbonate of soda)100g
- Natural soap bar, finely grated80g
- Essential oil (optional)30–50 drops
- Bring 2 litres of water to the boil, then remove from heat and allow to cool to approximately 80°C.
- Add grated soap to the hot water and stir continuously until completely dissolved — approximately 3–5 minutes. The soap must dissolve fully before adding other ingredients.
- Add sodium carbonate and stir until dissolved. Then add baking soda and stir again. The mixture will foam slightly.
- Allow to cool to room temperature. The concentrate will thicken as it cools — this is normal. Some separation may occur; stir before each use.
- Add essential oils to the cooled liquid and stir well. Transfer to a sealed, labelled container. Store in a cool, dark place for up to 4 weeks.
- Standard load60–80ml per wash
- Front-loader HE40–60ml — add to drum directly
- Pre-treatmentApply undiluted to stain, leave 15 min
Stain Pre-Treatment with Sodium Carbonate
For tough stains, sodium carbonate used directly as a paste before washing dramatically increases removal effectiveness. The concentrated alkaline exposure breaks down stain compounds that the wash cycle alone may not shift.
- Basic paste: Mix 1 part sodium carbonate with 1 part warm water to form a thick paste. Apply directly to the stain, work in gently with a soft brush or fingers, and leave for 15–30 minutes before washing as normal.
- Soak method (for white or light-coloured fabrics): Dissolve 50g sodium carbonate in 1 litre of warm water. Submerge the stained item and soak for 1–2 hours before washing.
- Works best on: Coffee, tea, wine, fruit juice, grass, sweat, blood (cold water only for blood — hot water sets protein stains), curry, and grease.
- Not recommended for: Silk, wool, or other protein fibres — the high alkalinity can damage protein-based fabrics. Use enzyme-based stain removers or gentle wool wash for these.
- Always test: On a hidden seam or inside fold before treating the front of a coloured garment.
Other Cleaning Uses for Sodium Carbonate
Sodium carbonate is one of the most versatile ingredients in an eco cleaning toolkit — far beyond just laundry.
Tips for Best Results
If you live in a hard water area (most of Australia's inland and suburban areas have hard water), increase the sodium carbonate to 500g and reduce baking soda to 200g in the powder formula. The extra sodium carbonate binds more calcium and magnesium ions, allowing the soap surfactant to work more effectively without being deactivated by mineral compounds.
You can check your water hardness by adding a few drops of liquid castile soap to a glass of tap water and shaking — if it foams easily and clears quickly, your water is reasonably soft. If it forms a white curd film and won't foam, your water is hard and you need more sodium carbonate.
For sensitive skin or babies' laundry: Reduce sodium carbonate to 200g and increase baking soda to 500g. Use a completely unscented, fragrance-free soap bar and omit essential oils entirely. The lower sodium carbonate content reduces alkalinity while the higher baking soda content maintains odour control. Add an extra rinse cycle to ensure thorough removal of all detergent residue.
For eczema-prone skin, running an additional rinse cycle is more important than the formula adjustment — detergent residue left in fabric is a significant skin irritant regardless of the ingredients used.
Cold wash tip: Sodium carbonate dissolves best in warm to hot water. For cold washes (below 30°C), pre-dissolve your measured powder in a cup of hot tap water and add the solution to the drum before loading clothes. This ensures complete dissolution and maximum cleaning effectiveness even in cold cycles.
Grey water safe? Yes — at standard wash concentrations, sodium carbonate is safe for grey water systems and septic tanks. The carbonate ions break down naturally in soil and do not accumulate. Avoid using white vinegar in the rinse cycle of grey water systems though — the acid-alkaline reaction produces carbonic acid and carbon dioxide, which can affect the microbial balance in septic systems over time.
Safe handling: Sodium carbonate at pH 11 can cause mild irritation to eyes and skin with prolonged contact. Wear rubber or nitrile gloves when handling the dry powder or concentrated paste, and avoid touching your eyes. Rinse affected areas with clean water if contact occurs. At standard laundry concentrations in wash water, it is safe and causes no harm to skin. Keep the dry product in a sealed container away from children.
Frequently Asked Questions
What is the difference between sodium carbonate and baking soda?
Sodium carbonate (soda ash) has a pH of approximately 11 — strongly alkaline, powerful for cleaning, water softening, and stain removal. Baking soda (sodium bicarbonate) has a pH of approximately 8.3 — much milder, better for odour neutralisation and gentle cleaning. In a laundry formula, sodium carbonate does the heavy cleaning work while baking soda adds gentleness and odour control.
Is homemade laundry detergent safe for HE washing machines?
Yes. This formula is low-suds and compatible with HE front-loaders and top-loaders. Use the lower end of the dosage (1 tablespoon / 15g per load) for HE machines and add directly to the drum rather than the dispenser drawer to prevent residue buildup. Avoid high-foaming liquid castile soaps or synthetics — the grated natural soap bar formula produces minimal suds which is exactly what HE machines require.
Can I use sodium carbonate on coloured or dark clothes?
Yes — at normal wash concentrations it is safe for most coloured fabrics. For the first wash of new or heavily dyed garments, test a hidden seam first. Avoid extended soaking of dark clothes in concentrated sodium carbonate solution as prolonged alkaline exposure can affect some dyes over time. For darks, reduce sodium carbonate to 200g and increase baking soda to 500g for a gentler formula.
Can I use homemade laundry detergent on wool and silk?
No — sodium carbonate is too alkaline for protein fibres (wool, silk, cashmere, alpaca). The alkaline environment can permanently damage the protein structure of these fibres, causing shrinkage, felting, and loss of softness. Always use a purpose-formulated wool wash (pH neutral or slightly acidic) for these fabrics. The baking soda version alone (omitting sodium carbonate entirely) is safer for protein fibres but provides less cleaning power.
How long does homemade laundry powder keep?
The dry powder formula keeps indefinitely if stored in an airtight container in a cool, dry place. Sodium carbonate is hygroscopic — it absorbs moisture from the air, which causes clumping. A clumped powder still works; simply break up the lumps before use. The liquid version should be used within 3–4 weeks due to the water content promoting potential microbial growth over time.
Is this formula suitable for a septic system or grey water reuse?
Yes — at standard wash dilutions, sodium carbonate breaks down into sodium and carbonate ions in soil and water, and is compatible with septic systems and grey water reuse. Use the minimum effective dose (1 tablespoon per standard load) and choose a simple, biodegradable soap bar. Avoid synthetic fragrance oils — stick to essential oils or no fragrance for grey water applications.
Shop Sodium Carbonate (Soda Ash)
Available in 3kg buckets for home use and 25kg bags for bulk DIY makers. Click & collect in Springvale South or delivery Australia-wide.
Everything You Need for Natural Cleaning
All available from Soapmaid Australia — delivered Australia-wide or click & collect in Springvale South, Victoria.
Cleaning Minerals