Laundry detergents

Overall score breakdown

Overall score is calculated from the following 10 scores for stain removal:

• Everyday grime
• Collar & cuff stains
• Tomato
• Grass
• Olive oil
• Make-up
• Engine oil
• Chocolate ice cream
• Baby food
• Blood

We only test in a front-loader machine now. Most products are now formulated for both machine types and previous tests have shown a correlation between performance in front and top loaders with front loader performance being better. It is fair to assume that if it a product performs well in a front loader it will perform well in a top loader.

How we test

We wash specially stained fabric swatches in our lab. These swatches are used by detergent companies and consumer organisations worldwide.

One swatch is stained with nut oil, milk and a colour pigment. This swatch is used to measure performance on “everyday grime”. The other swatches test a detergent’s cleaning ability on nine common stains: collar and cuff grime, grass/mud, olive oil, make-up, chocolate ice cream, baby food, tomato, engine oil and blood.

We measure the recommended amount of detergent for a normally soiled load and used this to wash test loads at 20⁰C, the most common wash temperature. Each load contains two swatches of each stain and each detergent is tested twice.

We test detergents in a “normal” wash cycle, which is what a consumer is most likely to choose for an everyday load. After washing, we measure how much of the stain was removed from each swatch.

The cost per wash is calculated using the manufacturer’s stated washes per pack. If the number of washes isn’t stated, there is no cost per wash. The reason for this is that it’s important for consumers know how many washes they will get from a product while in the supermarket aisle to make a fair comparison of products easier.

We include a wash using only water as part of our test so you can see how the products compare to washing with no detergent.

Cold vs warm water

In previous tests, we’ve tested some detergents using warm water (40°C) to check whether there’s any difference in performance.

Overall, we saw a small improvement in dirt removal when using warm water, but it depends on the type of stain you’re trying to remove. Some detergents perform better in cold water than warm with some stains. For example, blood stains tend to set in warmer water so you’re better off tackling these with a cold wash.

Other ratings

We also assess product packaging and claims made on the product. We award a rating of good, acceptable or poor. This doesn’t contribute to the overall score:

• Packaging: assesses what the packaging is made of, how recyclable it is in New Zealand and how clearly it’s labelled with recycling information.
• Environmental: considers whether it claims to be biodegradable, septic tank safe or grey water safe and if a standard is stated.
• Safety: we look at whether the packaging has important safety information such as the poisons centre phone number, instructions on what to do if ingested, gets in eyes or on skin and if ingredients are listed.