How we test laundry detergents

The rigorous testing that helps you find the best laundry detergent for your washing machine.

Laundry detergent testing explained

We test hundreds of laundry detergents a year, and we test them at least once a year because they, and your washing machine, are the key to clean clothes. They also make up a third of the running cost of your washing machine. Why do we need to test so often? While you may have your favourite detergent that you've been using forever, that brand's current formula probably has no relation to how it was formulated five years ago. Advances in chemical technology mean that you can't rely on your favourite brand to stay the same, because they're always trying to beat the competition - which is why we test so often.

One of the big questions is what kind of stains is your laundry detergent best for? This depends on the stain type and the detergent. Are you an auto mechanic? Do you work in a surgery, do you have children, regularly spill chocolate ice cream or are you a chef? They'll all call for different types of stains. It's also why we ask you via Voice Your Choice which stains you get most, so you can decide which stains we test against.

Our expert testers

With over 30 years' experience in the laundry lab, we're proud of our expert testers. They've seen all types of laundry detergents come through the labs, but one thing never changes – they need to find what gets your clothes clean. We focus on the basics so that when it's time to buy, you can be sure the laundry detergent you buy will work well.

How we choose what we test

Why do we choose one laundry detergent over another? There are a number of reasons for this, but our priority is to test what you'll see in the retailers. That means that sometimes we might not cover a brand that sells directly, and instead focus on the big brand models that you'll most likely see in the retailer. That means you can at least see it before you buy it and see if you're happy with it. How do we know what's in retailers? We check current market figures to see what's selling well. We'll also include models that you've requested – if a lot of members want it, we'll test it.

Once we know what you want to read about, our buyers go out and use your member fees to buy the laundry detergents from a variety of retailers, then bring them in as is. This means we get what you'd get, so we can be sure the results are what you'll find rather than potentially 'tweaked'.

How we test

Contrary to popular opinion, we don't get CHOICE employees to bring in their dirty laundry. We use set loads of cotton materials, and attach a variety of stains to them. These stains are made in the Netherlands and include 10 that you tell us are the most common in your households. Why do we use pre-stained swatches of cloth? Because if you want to compare laundry detergents fairly, you have to use the same conditions for all of them.

The swatches of cloth that are embedded with a specific amount of dirt are identical and made up of a very specific formula. These are used all over the world by large detergent makers, plus other consumer organisations and are considered a standard in testing detergents. Using these is a means to minimise the amount of variables so you can see which detergent comes out best when comparing them.

After we put the recommended dose of detergent in either a front or top loader (we have four identical of each washer so there is minimal difference in machine type), we use a cold wash (20C) on a standard wash to get our main score. Sometimes we also run a warm wash on the highest and lowest scorers to see what difference it makes, as there are still many people who use a warm wash. We don't do this all the time, due to timing and the fact that we know most people are moving to a cold wash.

Once we run the wash, we retrieve the stained swatches and compare how clean they are post wash to how dirty they were pre-wash. We use a spectrophotometer to measure the difference which is a better measure than the human eye.

Stain selection and weighting

This is the list of swatches we use, as chosen by you, our members. They usually change every few years in response to surveys we send to out to members.

  • General detergency (35%)
  • Sebum - natural oils, perspiration (20%)
  • Grass/mud (15%)
  • Olive oil (6%)
  • Tomato (4%)
  • Makeup (4%)
  • Chocolate ice cream (4%)
  • Baby food (4%)
  • Mineral oil (4%)
  • Aged blood (4%)

Why don't we test smell?

There are a variety of reasons for this, but it mostly comes down to subjectiveness. Some detergents are strong sellers in the market, so we assume many people don't care about the smell, or don't think it's strong. There would be other people who do think a smell is overpowering. How do we make an assessment on what's strong and what's OK?

I've contacted professional fragrance makers about this aspect, and really they could only tell us what the fragrance is supposed to be representative of in terms of fragrance type (lemon, orange, etc), not strength of smell. Again, because what they consider strong could be quite different to what someone else considers strong.

This will also depend on how old the detergent is - the newer the box is the more likely it is to be a strong smell, whereas over time this will fade. Many manufacturers don't tend to be transparent about when something is made, so if we found one was strong, and another was weak (assuming we even could) then it could be based on how old the box is. And that kind of assessment wouldn't be fair to the manufacturer or our members.

Your best bet for the moment is to take the smell test in the retailer, assuming you can take the container far enough away from the pungent smell that is the detergents aisle. No, we aren't advocating opening the box in the retailer, but often smell permeates through the cardboard of boxes, and the lids can be opened - as long as they aren't secured with a twist top - of bottles to take a whiff.

Our test lab

We maintain a lab that is up to date with the latest reference machines and calibrated measurement tools for our testers to bring you the right results.

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