Which laundry detergent is best for washing clothes?

When Consumer NZ put 46 laundry detergents to the test recently, researchers found three were no better than using water.

The products were tested against various stains (olive oil, baby food, tomato, grass/mud, sweat and “everyday grime”) with the three lowest-ranked scoring ‘poor’ for getting rid of most of these stains. To put it into perspective, water was rated ‘average’ for grass/mud and baby food stains and ‘poor’ for the remainder.

But people need a detergent that ranks well on all measures for a stress-free washing cycle that doesn’t involve sorting your clothes based on stains, says AUT associate professor of chemistry Jack Chen.

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Chen says detergents contain surfactants - chemicals that are good at removing dirt and oily substances. So, water alone – like the lowest-ranked detergents – is less likely to be effective at doing that.

Consumer NZ head of testing James le Page said the two laundry sheets tested ranked no better than water.

“They only weigh a couple of grams, so when you put them in your machine, they’re just not going to do a good job compared with a capful of laundry liquid or scoop of powder, both of which have the potential to contain more active ingredients.”

Chen believes that’s because sheets are a more recent development, so their formulations aren’t as advanced as the others.

While powders, liquids and pods are all generally effective, liquids don’t contain as much alkaline builders (chemicals that improve the detergent’s effectiveness by controlling the levels of pH) as powders do, he says.

“The alkaline builders are generally solids that is easier to formulate within a powder, so you can't actually have them inside the liquid. So the liquid-based detergents are mostly water and surfactants, so they're usually quite good on like greasy and oily stains.

“With the powders that contain more of these alkaline builders that help the effectiveness of the surfactants, they are quite good at removing like mud and clay and kind of ground-in dirt.”

The Housekeeper cleaner Rachael Quin says modern machines will recommend which product to use and for which cycles. Some detergents also outline whether they're more suited for a front loader versus a top loader machine.

“It used to be we just had washing powder or washing liquid but now there's bacterial agent and now there's dryer sheets and there's fabric softener and it's just a lot. I think like most of my ethos for cleaning is ‘less is more’.”

Adding more doesn’t result in cleaner clothes, Chen says. Instead, the detergent that holds on to the dirt isn’t washed away properly.

“So, you essentially have that kind of accumulating with your clothes even after the wash.”

Quin says people are often using too much detergent and fragrance in the wash.

“You might be wasting detergent, more than likely, or you might be putting in too much and it’s not able to rinse through the clothing enough and then that could cause a skin irritation, or it could just not clean the clothes as well as you think.”

Surfactants and alkaline builders are some of the standard ingredients, Chen says.

But enzymes (like amylases and proteases), found in more advanced formulations, are good at removing starchy stains, blood and sweat, he says.

“Generally, I think most of the high-end [detergents] … would contain enzymes in addition to the bulking agents and the builders.”

Christchurch-based ‘Queen of Clean’ Sonia Barrish makes her own cleaning detergents and has a recipe for a laundry one.

“My husband unblocks drains for a living, so he gets very muddy and dirty and [the DIY detergent] works on all that stuff and then I use it like on our cloth nappies as well and it's really great on that too.”

Chen says soap is a surfactant that is good at getting rid of “general oily stains” and makes for a good combination with washing soda (sodium carbonate, an alkaline builder).

“What a lot of these DIY detergents won’t contain are the additional enzymes that can help break down the specific stains – things like starchy stains are quite hard to break down, and blood, protein-based stains.”

For tough stains, Barrish says she might choose to lather it up with Castile soap ahead of throwing it in the washing machine or soak in washing soda.

“There is a concern for septic tanks with the sodium carbonate, but the amounts that you'll use [for washing or soaking], it's not gonna upset the septic tank balance.”

Quin says DIY products are good economic value for people on a budget, those who have big families or need to do a lot of washing often. But you’d need to consider the time and effort involved, space to store leftover ingredients, and whether you’ll stick with it.

“I do like the idea of some of these DIY laundry detergents because you know exactly what you're putting in there, you can control it, and I think … the less ingredients we have in things, it's better for us holistically.”