How manufacturers make smartphones waterproof

History is populated by unfortunate anecdotes involving mobile phones and water.

There are tales of phones that fell into the sink while applying hair dye, handsets falling out of trouser pockets while boarding a boat, and so on.

A few years ago, each tale would have had a sad conclusion as a combination of hairdryers, silica gel pads and cotton wool buds failed to bring the device back to life.

Owners would be left with an expensive paperweight, and the growing realisation that almost everything on their device had been lost forever.

Happily, handset manufacturers quickly recognised that phones will occasionally end up in the washing up bowl, the swimming pool and even the toilet.

Indeed, over a third of all device repairs in the UK last year are estimated to have involved liquid damage.

As such, waterproof smartphones have become a key differentiator in what’s otherwise a fairly generic marketplace full of handsets which perform the same functions equally well.

Apple’s iPhone 7 and Samsung’s Galaxy S7 were among the first mainstream devices to abolish the need for separate waterproof casings, and other manufacturers have followed suit.

However, waterproof smartphones deliver differing degrees of protection…

The proof is in the pouring

There are two types of smartphone waterproofing.

Splash-proof handsets are designed to cope with being used in the rain, or those annoying moments where turning on a tap splashes water everywhere.

Fully waterproof smartphones are intended to be submersible – suitable for taking photos while snorkelling, or accompanying you into the shower.

Different devices offer varying levels of protection, albeit generally falling into one of these two categories.

However, to avoid factors like exceptionally salty water affecting their resistance and leading to customer complaints, manufacturers refer to water-resistance rather than waterproofing.

An Ingress Protection rating is applied to smartphones, indicating how effectively they’ve been sealed against both moisture and dust.

Oddly, the dust rating comes first. And confusingly, different numerical values are applied to each category.

The highest IP rating a dust-proof smartphone will receive is 6, which should support taking pictures in the middle of an Arabian sandstorm.

Waterproof ratings go from 0 to 8. The latter covers protracted immersion in more than one metre of water, which becomes increasingly pressurised as you descend from the surface.

The first three ratings effectively insure against rain and mist. A 4 rating means the device is splash-proof, whereas a 6 should be able to withstand a 12.5mm nozzle jet for three minutes.

Do bear in mind that ratings are allocated in response to laboratory testing, whose conditions may be rather different to attempting an underwater selfie in the Dead Sea.

(If either the dust or moisture protection is listed with an X instead of a number, it hasn’t been officially tested and graded yet – often an issue on newly-launched handsets.)

Sealed with a kiss

Every device’s outer casing is assembled from at least two separate parts, like bonding together the halves of an Easter egg. And where there’s a join, there’s an inherent weakness.

Manufacturers have found two ways to protect these seals against particle ingress. One involves sealants, and the other requires a nano-coating.

At present, the latter is only capable of splash resistance, though scientists are attempting to develop nano-coatings which support immersion in up to a metre of water for 30 minutes.

Airtight adhesive seals across the device’s body currently represent the best barrier against water damage, such as water-resistant glue around screens and rubber O-rings behind sockets.

Phones featuring this level of protection tend to be high-end models like the Samsung Galaxy S10, Google’s Pixel 3 and the Sony Xperia XZ3.

Even so, the vagaries of immersion mean manufacturers probably won’t offer repairs under warranty if a device ends up damaged as a result of protracted or repeated immersion.

And if exposure to water is a daily part of your job, you might be better investing in rugged waterproof smartphones, like Caterpillar’s impressively specified Cat S61.