Borax in laundry: what it is and how it works
A natural water softener that boosts detergent in laundry and softens fibres.
Borax is the common name for decahydrate tetraborate disodium (Na2B4O7·10H2O), also known as sodium borate. It's a white, crystalline powder that dissolves in water and has been a staple in home laundry guides for decades.
It's not the same as boric acid, sodium perborate (a popular oxygen-based bleach, CAS 10486-00-7), or washing soda or calcined soda: each of these substances has different pH and a different mechanism of action.
In this article, you'll learn what borax is, whether using it in laundry is safe for children, pets, and sensitive skin, and how to dose it.
1303-96-4
1330-43-4
215-540-4
9.3-9.5 (mildly alkaline)
Repr. 1B H360FD, Eye Irrit. 2 H319 (GHS08 pictogram)
Water softener and detergent booster, not a bleach
Borax's properties in laundry stem from its mild alkalinity: an aqueous solution has a pH of around 9.3-9.5, which creates two effects.
It softens water: borate ions bind calcium and magnesium responsible for water hardness, so fewer calcium soaps deposit on fibres and rinsing is more effective. It also boosts detergent by raising the pH of the bath, which favours alkaline laundry enzymes with pH optimum in the 8-10 range.
Borax is not a bleach: unlike sodium perborate, it doesn't contain a peroxide group and doesn't oxidise dyes. The brightening effect on laundry is more a result of better removal of hard water deposits and grease, not a reaction with stains.
Is borax safe?
For children, pets, and sensitive skin
The CLP classification Repr. 1B H360FD applies to borax: it marks a substance that may harm fertility and the developing child. Context matters, however. The classification refers to long-term or occupational exposure to the pure substance, not a single use in home laundry.
That's why consumer sales of borax in the EU are restricted by REACH regulations (Annex XVII, entry 30): mixtures with over 0.3% by weight of Category 1A or 1B reprotoxic substances don't reach consumers. This is a systemic safeguard, not a signal that laundry with borax is unsafe.
Real risk lies in eye or skin irritation from direct contact with the dry powder, consistent with Eye Irrit. 2 classification. Borax is not a typical contact allergen.
Do
- Wear gloves when scooping dry powder to avoid eye and skin irritation
- Dissolve borax in warm water before adding to the drum or drawer
- Store in a sealed, original container, away from children, pets, and food
Don't
- Don't confuse borax with baking soda or washing soda: these are different substances with different pH
- Don't mix with strong acids or chlorine bleach without checking the safety data sheet
- Don't use undiluted borax on wool and silk: high pH weakens protein fibres
How to dose borax in laundry
Step by step: quantity, temperature, and common mistakes
Borax works well in three situations: as an additive to main wash in hard water, for soaking protein and fatty stains, and for refreshing laundry. The quantities given are home practice, not a technical standard: exact dosing depends on water hardness and the detergent maker's recommendations.
You always add borax together with a normal dose of detergent, never instead of it: it contains no surfactants by itself.
- 1
Dissolve borax in warm water
Measure 1-2 tablespoons (about 15-30 g) per load and dissolve in warm water before laundry goes in.
- 2
Add with detergent
Pour dissolved borax into the drum or drawer alongside a normal dose of detergent, wash at 40-50°C.
- 3
Adjust dose to use
For soaking stains use 2 tablespoons per litre of lukewarm water (about 30°C) for 30-60 minutes; for refreshing in hard water 1 tablespoon is enough.
This white powder is a laundry booster, not a standalone cleaning agent or bleach: it softens water and raises bath pH, but won't remove dye stains or greasy technical stains as effectively as a dedicated stain remover.
A professional laundry has dedicated water-softening systems using ion exchange and tailors chemicals to the fabric. With delicate materials like wool, silk, suits, or coats, home experiments with borax carry risk because of high pH: it's better to trust specialists.
Now you know the theory. Practice can be less forgiving.
If you would rather not risk your favourite piece, leave it to the specialists at Gorące Żelazko laundry in Lublin.
Frequently asked questions
These are two different substances with different mechanisms: borax solution has pH 9.3-9.5 and is distinctly alkaline, baking soda is much weaker alkaline. Borax softens water and binds hardness ions, baking soda mainly neutralises odours and gently scours. They are not 1:1 interchangeable.
It dissolves best and works most effectively in warm water, around 40-50°C for main wash. For soaking stains, lukewarm water, around 30°C, is adequate.
There are no verified sources of machine damage from proper use. The key is not to pour dry powder directly into the drum, but to dissolve it in water first.
You'll find it in drugstores, chemists, and chemical suppliers. Consumer sales are subject to REACH restrictions due to borax's reprotoxic classification (described in the safety section), so concentrated commercial packs have limited availability.
About the author
Małgorzata Małecka
Owner of the Gorące Żelazko laundry
Małgorzata Małecka runs the Gorące Żelazko laundry in Lublin. Together with her team, she makes sure customers' clothes, shoes and fabrics come back clean and in the best possible condition.
