9 amazing machines we use to uncover Which? Best Buys

At Which?, we leave no stone unturned in our tests. We put products through their paces with the most rigorous test programmes, and utilise some pretty ingenious machines.

Unlike other review sites, we independently test products under strict, lab-controlled conditions. That means making the most of advanced machines, from a child car seat crash rig to an enormous wooden barrel used to test mattresses.

Below, we lift the lid on some of the most eye-catching testing equipment from our labs, and hear directly from our expert Scientists to see what really makes a Which? Best Buy.

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1. Smartphones – the robotic arm

'Battery life is a key feature we think about when purchasing a new phone – we all know the struggle of forgetting to charge our mobile and having to get by on that final 10% charge. To save you from buying a phone that needs plugging into the wall too often, we use a nifty robotic arm to mimic how people use their mobiles on a typical day, from making calls to watching videos and taking pictures.

'With our willing robo-assistant, we can see exactly how long a phone's battery will last. The multi-talented robotic arm is also used to test foldable phones, opening and closing them 30,000 times (yes, really) to check the durability of the hinges.'

Jus Rai, Scientific Advisor, Which?

• Best Buy performance: The battery will take longer to drain while the robotic arm performs its various actions during the test cycle.
• Don't Buy drawbacks: Don't Buys typically will discharge a lot quicker with a much shorter battery running time.

2. Mattresses – the spine alignment test and rolling barrel

'Our mattress testing equipment might look like it belongs in a medieval torture chamber, but it’s actually been designed to test whether mattresses offer good body support over their lifetime.

'A good mattress will keep your spine in the same position when you’re lying down as when you’re standing up, whether that’s on your back, front or side. In fact, we measure the shape of the spine at 36 different places when standing up and then again when lying down. Plus, we use different body types to check that the mattress is supportive for everyone.

'To make sure your mattress will stand the test of time, we roll heavy barrels across every mattress 30,000 times to simulate around 10 years of tossing and turning. Doing this by hand wouldn't be much fun, so we use automated equipment instead. This also means we can simulate 10 years of use in just 24 hours.'

Dr Steph Kipling, Science Team Manager, Which?

• Best Buy performance: Best Buys typically provide good support for your spine in most, if not all, sleeping positions over the life of the mattress.
• Don't Buy drawbacks: Don't Buys typically fall down in important areas by being either unsupportive or unable to stand the test of time, or both.

Find out which mattresses offer plenty of support with our expert mattress reviews.

3. Pushchairs – the rolling road

'The ‘rolling road’ in our pushchairs test lab is a continuous treadmill that features bumps along the track, but we don't use it to burn calories. Instead, we put pushchairs through their paces by rolling them along the belt for 72,000 cycles, or 96,000 for pushchairs designed to carry older children. That’s equivalent to over 200km, which is the same as walking from London to Birmingham – quite a trek!

'Each model is fully loaded with weights in the seat and basket, so we hear plenty of clanking as the pushchairs roll over those bumps. Thankfully, we've seen many models survive the rolling road over the years, although occasionally the wheels do fall off – literally. If we spot any durability issues, you can be sure you'll hear about it in our full review.'

Kamisha Darroux, Principal Scientific Advisor, Which?

• Best Buy performance: A high-scoring pushchair will remain intact and be fully functional after its time on the rolling road. A little wear and tear on the wheels is understandable!
• Don't Buy drawbacks: A Don’t Buy pushchair usually has its wheels falling off, cracks within the frame, screws falling out and some even collapse completely.

4. Child car seats – the crash rig

'We’ve specially designed our child car seat tests to find the best models that protect in a crash, even going beyond the legal minimum standard. Our test rig zooms forward at 40 mph and then collides with a panel to simulate a head-on collision.

'Each child dummy has sensors attached to its body and we use these to analyse the forces exerted. The data from our crash rig lets us assess potential injury to a child in a crash, including whether the child’s head is protected, if the seat belt cuts into the neck or stomach, and if the car seat breaks during impact.'

Kamisha Darroux, Principal Scientific Advisor, Which?

• Best Buy performance: The child car seat will remain completely intact without any breaks or cracks on display. The body sensors should not flag up any extreme forces on the dummy.
• Don't Buy drawbacks: A Don’t Buy might break under the pressure of forces exerted in our simulated crash. It also might not provide enough support for a child’s head in a side-on crash.

We test harder in the lab so you can choose the right child car seat when you shop. See our child car seat reviews.

5. Vacuum cleaners – the dust trolley

'The most important feature of any vacuum is its ability to pick up dust. To test this, we weigh out some dust and use a high-tech trolley to spread it evenly across a carpet. We then go over the carpet with a roller that embeds the dust – just as you would do at home by walking on it.

'To make sure all vacuums are tested the same way, we use an advanced rig. The vacuum’s nozzle is pushed horizontally along the carpet and moved back and forth at a consistent speed. Specialised sensors hidden under the test floor measure how hard it is to push the vacuum.

'We also measure the weight of the dust receptacle before and after the test so we know how much dust has been picked up. Oh, and we repeat this test using real pet hair, too.'

Monika Gil, Senior Scientific Advisor, Which?

• Best Buy performance: Best Buys glide effortlessly across the carpet while picking up almost all the dust and pet hair.
• Don't Buy drawbacks: Don’t Buys require a lot of force to move and have weak suction power meaning lots of dirt is left on the carpet.

6. Washing machines – the spectrophotometer

'In our washing machine testing, we use an instrument known as a spectrophotometer. Yes, it sounds technical and possibly like something you’d find in an 80s sci-fi blockbuster, but it's actually an instrument that we use to measure washing efficiency.

'The machine is designed to see colour the way we do – it uses a light source to illuminate fabric samples (stained with substances including oil, grease and blood) and measures reflection and absorption. The darker or dirtier the clothes, the lower the reflectance.

'Our spectrophotometer produces spectral data of different wavelengths, which can be used to determine the degree of stain removal. In other words, we can calculate the cleaning power of each washing machine and compare it to our reference machine.'

Jus Rai, Scientific Advisor, Which?

• Best Buy performance: Best Buys will remove the stains with a much greater efficiency, meaning they would typically have a higher reflectance measurement which can be detected by the machine.
• Don't Buy drawbacks: Washing machines will have a much lower ability to remove the stains and therefore would produce lower reflectance scores from the machine.

To see which washing machines will clean your clothes without costing a fortune to run, consult our washing machine reviews.

7. Irons – the test rig

'Ironing that towering pile of laundry you’ve been avoiding can feel like a daunting task, but our tests reveal the irons that make your laundry days less of a chore. We strap irons to a rig that can simulate 16 weeks of ironing in just 252 hours.

'We iron a variety of creased laundry items including cotton shirts, light cotton skirts and linen trousers, measuring how easy it is to eliminate pesky creases. Then, we go one step further and iron our way through more crumpled fabrics, applying the average weight of a human arm to see how good an iron is with just a few swipes of the soleplate. Thanks to our testing rig, you can spend less time ironing and more time doing things you enjoy.'

Ruby Gordon, Scientific Advisor, Which?

• Best Buy performance: Best Buy irons are easy to use and can quickly smooth out creases with minimal effort required.
• Don't Buy drawbacks: Don't Buy irons make ironing hard work. They require much more time and effort to get rid of creases, meaning you’ll be pressing down harder, for longer and will likely be left with crumpled clothes.

8. Headphones – the rubber ear

'We thoroughly investigate headphones to measure technical performance and real-world experience. Our tests use a specially-designed mannequin head and torso – it has realistic rubber ears and an ear canal modeled on measurements from hundreds of thousands of people to accurately replicate the structure of a human ear.

'Our tests go the extra mile to measure real-life performance. That's why we secured permission from Transport for London to take live recordings at various tube stations, both inside the train and on the platform. These enable us to test the clarity of the headphones when faced with serious background noise to create an authentic user experience.'

Ruby Gordon, Scientific Advisor, Which?

• Best Buy performance: Best Buy headphones will give you great sound quality without letting those around you also hear what you're listening to. They'll also be comfortable to wear and cancel out external noise well to maximise your listening experience.
• Don't Buy drawbacks: Don't Buy headphones will leave you disappointed with poor performing sound quality, unnoticeable noise cancellation and high sound leakage.

A Best Buy pair of headphones are the perfect travel companion – see our headphones reviews for top picks.

9. Washing-up liquids - the scrubbing machine

'Removing grime from your cookware is often a tricky challenge, requiring plenty of elbow grease and washing-up liquid. We treat all washing-up liquids the same in our tests to find out which is the best at removing burnt-on grease.

'In the lab, we use an automated scrubbing machine that consistently applies pressure whilst mimicking how we would scrub kitchenware. The test rig moves washing-up liquid coated sponges back and forth over stainless-steel tiles coated with baked-on grease until they are scrubbed clean. It can take over 100 cycles to remove that burnt-on food – thank goodness we have automated equipment to get the job done.'

Dr Neal Rimmer, Senior Scientific Advisor, Which?

• Best Buy performance: Our machine is able to remove tough, burnt-on grease with a minimum amount of scrubbing.
• Don't Buy drawbacks: Poor-performing washing-up liquids struggle to remove burnt-on grease, meaning you should steer well clear.

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