NURO Knowledge

Most people clean their glasses the wrong way – with a shirt hem, a paper towel, or a dry wipe across the lens. This guide explains why that damages coatings over time, which methods are actually safe, and how ultrasonic cleaning works.

Standard washing-up liquid is counterproductive in an ultrasonic cleaner: it creates heavy foam that demonstrably disrupts the cavitation effect – the actual cleaning mechanism. Manufacturers also explicitly warn against household cleaners in their devices.

An ultrasonic cleaner uses high-frequency sound waves (typically 40,000–48,000 Hz) to generate millions of microscopically small bubbles in a liquid. As these bubbles implode, they create a mechanical cleaning effect – with zero friction on the surface. This effect is called cavitation.

All three methods have their place – but different strengths. Microfibre cloths and sprays are quick and portable but can't reach every groove and carry a residual risk of fine scratches. Ultrasonic cleaning is contact-free and more thorough, but tied to a device at home or at the reception desk.

Clean glasses are more than a hygiene question – they're part of a well-groomed overall appearance, just like well-kept hands, teeth or hair. In professions with direct customer contact especially, smudged, greasy lenses stand out quickly in conversation.

If the same water-and-concentrate fill is used for multiple pairs of glasses in a row, grease, skin particles and dissolved dirt increasingly build up in the liquid. There's no exact 'change after X pairs of glasses' rule – visible and detectable signs matter more.

Ultrasonic cleaning is contact-free, thorough and fast – but it isn't the right solution for every situation. An honest weigh-up before you decide to buy one.

There's no single right answer – the right frequency depends on how you use them. Sports glasses, ideally after every sweaty session; everyday glasses, once or twice a week.

Yes, with important exceptions: gold, silver and most gemstones handle the cleaning without issue. Soft stones like pearls, opals or amber, as well as glued settings, should not go in an ultrasonic cleaner. Watches only if they're waterproof.

Polarizing and mirror coatings sit as an ultra-thin extra layer on the lens and are especially prone to scratches and peeling if cleaned incorrectly. Contact-free ultrasonic cleaning is the safest method here.

Sweat contains dissolved salts (mainly sodium chloride) that crystallize on your glasses as they dry. These crystals act like fine sandpaper the next time you wipe them, and also settle into hinges, where they can contribute to corrosion.

Anti-reflective coatings are ultra-thin, multi-layer treatments that reduce glare – and are therefore more scratch-sensitive than uncoated glass. Contact-free cleaning is the gentlest method here.

Beyond glasses and jewellery, plenty of small everyday objects are suitable for ultrasonic cleaning: razors and blades, combs and brushes, small tool parts, model-building pieces and coins.

For daily use at a reception desk or in a workshop, the effort involved is minimal: loading takes seconds, the cleaning cycle runs unattended for 180 seconds, and the water only needs changing when visibly dirty.

Toothpaste and baking soda are often recommended as 'gentle' lens cleaners – in reality, both contain fine abrasive particles that cause permanent micro-scratches. Vinegar can help with limescale spots on uncoated lenses, but attacks many modern coatings.

Standard washing-up liquid is optimised for heavy foaming and grease-cutting during manual washing. A dedicated ultrasonic cleaner concentrate, by contrast, is deliberately low-foaming, usually pH-neutral, and formulated for material compatibility with lens coatings.

Bacteria are everywhere – on your glasses, your smartphone, your keyboard, even in the fridge. This overview breaks down where the highest bacterial load in everyday life actually lurks, what studies really show, and which simple measures demonstrably help.

Two studies from Furtwangen University show: worn glasses are densely colonised with bacteria. The more comprehensive study from 2020 found 5,232 different bacterial species from 665 genera on just 30 pairs of glasses examined. More than 80% of the most common species are considered potentially pathogenic. In an earlier study by the same research group, damp cleaning reduced the bacterial load by up to 95%.

The toilet isn't the germiest spot in the house – mop heads, sponges and cutting boards are. A data-based overview of the most heavily bacteria-laden everyday objects, from smartphones to handbags.

According to Germany's Techniker Krankenkasse health insurer, an average smartphone hosts around 100 different bacterial species; individual studies have found up to 173 species plus eight fungal species on single devices. The reason: we touch our phones several hundred to over 2,500 times a day – usually without washing our hands first.

The desk is often seen as a clean place – but keyboards, phones and door handles frequently carry more germs than a toilet seat, simply because they're rarely cleaned. According to research cited by the US outlet MarketWatch, an office phone was found to carry over 1,600 bacteria per square inch, a hand-washed mug handle 2,200 – a toilet, by comparison, only 59.

Dirty glasses are a hygiene topic (see the Furtwangen studies), but not a direct infection vector for the eye, since they rest externally on skin and nose. Contact lenses, according to the German Ophthalmological Society (DOG), are a 'foreign body in the eye' with a significantly higher, well-documented infection risk when hygiene is lacking.

From recycled PET in microfibre cloths to the question of whether synthetic textiles are really the more eco-friendly choice: an overview of materials in eyewear care and what actually makes them sustainable.

rPET is made from collected PET bottles that are sorted, cleaned, shredded into flakes, melted down and spun into new fibres. According to the Waste and Resources Action Programme (WRAP), production requires around 59% less energy and produces about 32% fewer CO2 emissions than making polyester from new crude oil.

Microfibres are spun so finely that they absorb grease and dust rather than pushing it across the lens – unlike clothing, paper or tissues, whose coarser fibres and additives can cause micro-scratches.

A microfibre cloth should be washed separately from towels and without fabric softener – softener and lint from other laundry clog the fine fibres and turn the cloth itself into a scratch hazard.

Cotton farming consumes enormous amounts of water (around 2,000 litres for a cotton T-shirt) and often relies on concerning pesticides. rPET requires neither farmland nor significant water in production, but is fossil in origin and sheds microfibres when washed. There's no across-the-board 'better' fibre – just different environmental trade-offs.

An honest answer, even if it's uncomfortable: a study cited by VerbraucherService Bayern found that recycled polyester can shed on average around 55% MORE microplastic particles when washed than newly produced polyester. rPET solves the crude-oil and waste problem – not automatically the microplastic problem.

Ultrasonic cleaners vary widely in size, power and suitability for eyewear. This guide breaks down the key buying criteria – deliberately brand-agnostic, without favouring any manufacturer.

The tank needs to hold the entire pair of glasses – including the fully opened temples – fully submerged, without bending or wedging them in. That matters more than the device's raw wattage.

Many opticians offer ultrasonic cleaning as a free service, recommended roughly every four to six weeks – but it requires an in-person visit each time. A device of your own costs more upfront, but lets you clean on your own schedule, as often as you like.