Ácido cítrico para limpeza doméstica — guia completo com dosagens

Citric acid — the "natural alternative" that actually works

Among the natural products on supermarket shelves there are only a handful that genuinely do the work they promise, and citric acid is at the top of the list. It's biodegradable, costs CHF 4–7 per kilo in bulk, and is backed by decades of technical literature attesting to its safety and effectiveness (E330 in Europe, GRAS in the United States). In a Swiss home, where water runs medium-hard and limescale is the chronic enemy, it's the one powder worth keeping permanently in the pantry.

What it is and why it works

Citric acid is a weak organic acid that occurs naturally in citrus fruits — lemon contains 5–7% — and the powdered version sold commercially is simply that same acid crystallised and standardised. Chemical formula C₆H₈O₇, pKa of 3.13, acidity comparable to vinegar. What makes it particularly useful for cleaning is the combination of proven effectiveness on limescale with a series of practical advantages over vinegar: it comes as a powder so it has no smell, it doses precisely, it costs less per useful application, and it keeps indefinitely in a dry sealed jar.

On the regulatory side it's solid: code E330 in the European Union as a food additive, GRAS status in the United States, complete biodegradability documented in the ECHA REACH dossiers and compliance with the EU Detergents Regulation (EC) 648/2004.

Where to buy it in Lugano

In supermarkets it's found in the bio or eco lines at Coop and Migros, in 500 g packs at around CHF 5–8: handy if you need it right away, but the per-kilo cost is higher. Drugstores and bio shops (Allnatura, BioCorner) sell 1–2 kg packs at CHF 5–7/kg, and online — Galaxus, Brack, Manor — 2–5 kg packs drop to CHF 4–7/kg, which is the best price if you use it regularly. At home, an airtight jar in a dry place is enough; it lasts essentially forever.

The main uses, with the doses that actually work

The recipes below cover the most frequent use cases in a Swiss home. The doses are the verified ones: less acid doesn't work, more acid adds nothing.

Washing machine and dishwasher

A monthly washing-machine descale uses 200 g of citric acid in total — 150 g distributed in the drum, 50 g in the detergent drawer — on a cotton cycle at 60 °C with no pre-wash. The full procedure, with when to do it and how to spot a washing machine that genuinely needs it, is in our washing-machine disinfection guide.

For a dishwasher gone yellow the same logic applies: 100 g of citric acid in the empty cutlery basket, intensive cycle at 70 °C. It's a deep clean of nozzles and pipes that you can't get from regenerating salt — it's a monthly or bi-monthly treatment, not a substitute for the salt.

Kettle, espresso machine, taps

The electric kettle is limescale's favourite victim in a hard-water home. The recipe is 50 g of citric acid in 1 L of water, boiled for five minutes, then rinsed two or three times. In Lugano and the Sottoceneri this needs repeating every two to three months if you drink a lot of tea or work from home.

The espresso machine follows the same dose — 50 g of citric acid in 1 L of water in the reservoir — but you trigger the manufacturer's automatic "descale" cycle; follow the manual because some machines need specific rinses. Final flush: two or three cycles with water only to remove any residue that could alter taste.

The taps are a small intervention that visibly transforms the kitchen and bathroom. Unscrew the aerator (the mesh under the spout), soak it for 30–60 minutes in 5% solution (50 g/L), rinse and screw it back. The limescale-clogged showerhead gets the whole head submerged in 10% solution (100 g/L) for an hour; on rinse, an old toothbrush takes off any residual scale and the flow returns to full.

Shower, glass and mirrors

For the shower enclosure the concentration is 10%, in a spray bottle: mist the walls, leave for 15–30 minutes, rinse with the hand shower. Stubborn stains call for a thicker paste — 100 g of citric acid with 50 ml of water — applied with a toothbrush on the localised spots.

For glass and mirrors the dilution drops to 5% (50 g in 1 L of warm water) in a spray bottle. Microfibre for cleaning, separate dry cloth for the finish: the secret to streak-free mirrors is drying immediately, in one direction, never in circles. For regular window cleaning, especially the high or rain-exposed ones, our window cleaning in Lugano guide covers the rest.

When NOT to use it: surfaces and mixes to avoid

Quick dosing reference

For those who'd rather hire a professional