Vinegar shifts limescale from a kettle. Soda crystals cut through a greasy roasting tin. Neither is much use at the other job, and the reason is the same: pH.
Knowing the pH of cleaning products tells you what a cleaner is built to tackle, which surfaces it can harm and why some products should never meet. Here's the scale in plain English, from citric acid to washing soda.
What the pH of cleaning products tells you
pH measures how acidic or alkaline a water-based liquid is, on a scale from 0 to 14. Pure water sits in the middle at 7, which is neutral. Below 7 is acidic and above 7 is alkaline.
The scale is logarithmic, so each whole number is a tenfold change. pH 2 is ten times more acidic than pH 3, and a hundred times more acidic than pH 4.
Typical pH of household cleaners
These are rough figures from public cleaning guidance. Individual products vary, so check the label or the safety data sheet.
- Lemon juice and white vinegar: around pH 2–3 (acidic).
- Plain water: pH 7 (neutral).
- Bicarbonate of soda in water: around pH 8–9 (mildly alkaline).
- Washing soda (soda crystals): around pH 11 (alkaline).
- Household ammonia: around pH 11–12 (alkaline).
- Chlorine bleach: around pH 11–13 (strongly alkaline).
Both ends of the scale need more care. Strong acids and strong alkalis can irritate skin and eyes and damage some surfaces, which is why their labels carry more warnings.
Acidic cleaners: citric acid and vinegar
Acids dissolve mineral deposits. Limescale is mostly calcium carbonate, and an acid breaks it down so it can be wiped or rinsed away.
That's why acids turn up in descalers, bathroom sprays and rust removers. White vinegar (acetic acid) and lemon juice (citric acid) are the mild kitchen-cupboard versions.
Citric acid: plant-derived and a chelating agent
Citric acid was first found in citrus fruit such as lemons and limes. Today most of it is made by fermenting plant sugars, which is why it's described as plant-derived.
It does two jobs. As an acid, it dissolves limescale and hard-water marks.
As a chelating agent, it binds the calcium and magnesium in hard water, so they interfere less with cleaning. Detergent makers use citrates as builders for the same reason.
Where acids don't belong
- Marble, limestone and travertine: these stones are calcium carbonate too, so acids can etch a dull mark into the surface.
- Metals left wet: acidic cleaners can corrode or discolour some metals, so rinse and dry afterwards.
- Greasy soil: acids on their own do little for fats and oils.
Alkaline cleaners: washing soda and ammonia
Alkalis are the grease shifters. They help break up fats and oily soil, which is why they're in oven cleaners, degreasers and many laundry products.
Washing soda (soda crystals)
Washing soda is sodium carbonate, sold in the UK as soda crystals. At around pH 11 it cuts grease on pans, hobs and drains, and it softens hard water in the wash.
It's strong enough to irritate skin, so wear gloves. Keep it off aluminium, which it can darken or corrode, and off wool and silk.
Ammonia
Household ammonia is ammonia gas dissolved in water, at around pH 11–12. It cuts grease and dries without streaks, so it turns up in some glass and hard-surface cleaners.
It has a strong smell, so open a window while you use it. And never use it alongside bleach (more on that below).
Neutral cleaners and where surfactants come in
Not every cleaner relies on a high or low pH. Many everyday cleaners sit nearer the middle of the scale and do their work with surfactants instead.
Surfactant molecules have one end that's attracted to water and one that's attracted to oil. They surround oily soil, lift it off the surface and hold it in the water so it can be blotted or rinsed away. For more on the plant-derived kind, read:
What are plant-based surfactants?
Why you should never mix cleaning products
Mixing cleaners doesn't make a stronger cleaner. At best the products cancel each other out, and at worst they react and release harmful gases.
Never mix bleach with acids or ammonia
UKHSA explains that bleach mixed with an acidic product, such as vinegar or some toilet cleaners, releases chlorine gas. Bleach mixed with an ammonia-containing cleaner produces chloramines. Both irritate the eyes, throat and airways.
HSE gives the same warning for workplaces: bleach mixed with acidic toilet cleaners or ammonia gives off harmful gases. For the full bleach safety rules, read:
Chlorine bleach vs oxygen bleach
Acid plus alkali just cancels out
Mix vinegar with bicarbonate of soda and you get a satisfying fizz. That fizz is carbon dioxide, and what's left is mostly water and a dissolved salt, with far less cleaning power than either started with.
Never-mix checklist
- Use one product at a time, and rinse or blot the area before switching.
- Don't pour different products down the same drain or toilet one after another.
- Keep products in their original, labelled containers, stored apart.
- Open a window while you clean.
- If products get mixed and you feel unwell, leave the property and call 999. If you're not sure, call NHS 111.
Choosing a cleaner for carpets, rugs and textiles
Fibres care about pH too. Wool carpet care guidance warns that highly alkaline cleaners can make dyes bleed and, in extreme cases, yellow and weaken wool fibres. Strong acids can damage cotton and rayon.
No single number suits every textile. Concentration, dwell time and rinsing all matter, so follow the care label and the product's directions.
- Read the care label on the carpet, rug or mat first.
- Check the product's safety data sheet: section 9 lists its pH.
- Patch test on a hidden area and check for colour change once it's dry.
- Use as little liquid as you can, and blot rather than rub.
Where STAIN LIFT fits
STAIN LIFT Ultra Strength Mat & Textile Stain Remover is made for mats and textiles and is labelled to eliminate stubborn wine, blood, oil & grime. It's built on plant-derived surfactants, not bleach. For a mark on a rug or mat:
- Prep: remove excess with a clean cloth.
- Apply: spray on the affected area.
- Dwell: leave for 1–2 minutes.
- Lift: work gently with a soft brush or scour sponge.
- Finish: wipe with a damp cloth and leave to air dry.
Always patch test on a hidden area first to check colour-fastness. Use it on its own, never mixed with bleach or another cleaner.
For how plant-based and conventional stain removers compare, read:
Plant-based vs conventional stain removers
Frequently asked questions
What is the pH of most cleaning products?
It depends on the job. Descalers and limescale removers are acidic, many everyday surfactant cleaners sit nearer neutral, and degreasers and laundry boosters are alkaline. Washing soda is around pH 11, household bleach around pH 11–13, and a product's safety data sheet lists its pH in section 9.
Is an acidic or alkaline cleaner better for grease?
Alkaline. Alkalis such as washing soda help break up fats and oils, which is why they're used in degreasers and oven cleaners, while acids such as vinegar and citric acid suit limescale and hard-water marks. On carpets and rugs, follow the care label and patch test first.
What is citric acid used for in cleaning?
Citric acid dissolves limescale and hard-water marks on kettles, taps, shower screens and glass. It's also a chelating agent: it binds the calcium and magnesium in hard water so they interfere less with cleaning. Keep it off marble and limestone, and rinse and dry metals afterwards.
Can you mix vinegar and bleach?
No. UKHSA warns that mixing bleach with an acidic product such as vinegar releases chlorine gas, and mixing it with ammonia produces chloramines, both of which irritate the eyes, throat and airways. Use one product at a time, rinse in between, and store products apart in their original containers.
Ready for the next spill?
Know the pH, know the job: acids for limescale, alkalis for grease, surfactants for lifting soil, and never a mix.
STAIN LIFT eliminates stubborn wine, blood, oil & grime on mats and textiles. It's plant-powered and biodegradable, with >30% plant-derived non-ionic green surfactants and vegetable extracts.
It's Made in Britain, an easy spray that revitalises fibres, and its safety data sheet shows it is not hazardous under GB CLP. It's available now; for the SDS or trade enquiries, email info@stainlift.co.uk.
