Whether soap nuts actually clean your clothes is heavily debated within the zero waste community. Some swear by them, but others say that they do not do anything. Here's what you need to know before using them…

Bag of soap nuts held out by a hand in front of street art

We lay bare the pros and cons of soap nuts shared by those who have successfully used them for years and those who have tried using them without success. We also look into the science behind soap nuts and see what studies done on their effectiveness have to say.

Is there a difference between soap nuts and soap berries?

No, there is no difference between soap nuts and soap berries. Both names are used to describe the same thing – the dried shell of berries from a variety of plants in the Sapindus plant family that contain saponin, which possess soap-like qualities and produces a lather when mixed with water, that are used as a natural, eco-friendly alternative to laundry powder and household cleaner.

How do you use soap nuts?

A few soap nuts are put inside a small bag that is usually supplied with them, this bag is securely closed and then placed in the washing machine together with your clothes. When agitated in water, the soap berries release saponin, which is a natural cleaner that “works as a surfactant, breaking the surface tension of the water to penetrate the fibres of your clothing, lifting stains from the fabric, and leaving dirt suspended in the water that is rinsed away”, according to Eco Nuts.

They can be made into a liquid concentrate by boiling them. It’ll take about 20 minutes of boiling for their natural detergent to be released, turning the boiled water into liquid soap. This liquid soap can be used as a base for liquid laundry detergent and other cleansers.

Read more advice on how to get the most out of soap nuts in the next section!

FOR SOAP NUTS: Those who go nuts for soap nuts say

A research paper (here) assessing the efficacy of soap nut as a scouring agent and checking the bursting strength of the knit fabric scoured with soap nut instead of detergent for industrial purposes, especially during the pretreatment of fabric has found that “soap nut could be a sustainable and cheaper alternative to synthetic detergent in knit fabric scouring method”.

This research on naturally soiled cotton fabrics that investigated the primary and secondary washing effect of soap nuts at different temperatures (60 and 90 °C) found “good washing performance of soap nut shells evaluated through primary effect was obtained especially at 90 °C”.

This study “establishes them as a potentially safe and eco-friendly source of saponins for processing cotton fabrics”.

In addition, the “multifunctional ability of saponins from herbal extracts [including soap nuts] for color protection and enhanced UPF [ultraviolet protection factor] of washed cotton and wool fabrics” was confirmed by this study, showing that they are gentler on fabric compared to standard detergents and commercial products.

Many zero wasters have used soap nuts for years and say their clothes come out of the washing machine clean, as long as they aren’t too dirty.

They are not recommended for dirty nappies, grubby kids clothes and very smelly gym and work clothes, as these will need something stronger. Some soap nut users say rubbing very dirty patches with a bar of soap or a paste of bicarb and water before washing solves this problem.

Those who use them recommend pre-soaking stained clothing and bleaching whites using percarbonate to keep them white, else they will start going grey after a while.

Some say that soap nuts need to be activated before use by soaking them in a cup of hot water before adding them to your cold-water wash cycle. A high spin is recommended to ensure agitation. You may also need to use a hot water cycle.

In addition, some say that they work better in a top loader and don’t work well in a front loader because there is not enough agitation.

They are an inexpensive option for washing clothes, as the same berries can be used for multiple loads, making them cost effective.

Some people like the fact that their clothing doesn’t have a chemical smell when they come out of the washing machine, however others don’t like the smell clothes washed with soap nuts have, finding it a bit weird. If you’re not a fan of soap nuts’ natural smell, those who use them recommend adding a drop or two of an essential oil to liquid soap nut laundry detergent.

The quality of the berries does apparently make a difference though, with sellers of soap nuts advising buying quality soap nuts for good results as these will have higher saponin content.

In other applications, the Sapindus Mukorossi species was used as a flow improver of heavy crude oil in this study and results were compared with a commercially available surfactant. It was found that the “addition of soapnut reduces viscosity and yield stress of crude by 87% and 83% respectively at 30 °C which is helpful for economical transportation of the heavy crude”. And in a study on the performance of two plant-based surfactants in the removal of heavy metals (Cu, Cd, Pb and Zn) from soil, “the overall performance of the batch washing process indicates that both surfactants were very effective in soil washing” and “the effectiveness of these surfactants is due to their ability to form micelles and subsequent removal of heavy metals from the soil surface by reducing the interfacial tension”.

AGAINST SOAP NUTS: Those who say using soap nuts is nuts say

The Choice website tested soap nuts and found that they were no more effective than washing your clothing in plain water. The website’s review of soap nuts, which can be found here, scored them an overall score of 42%. However, the method used is questioned.

There is the argument though that soap nuts need to be activated in or used in hot water and they were only used in cold water for Choice’s test. Also, they used a front loader for the test, which some say soap nuts don’t work in because there is not enough agitation. According to soap nut sellers, the quality of the soap nuts used would have also made a difference to the results and this is uncertain as the researchers do not say where the soap nuts used for this review came from and what the soap nut species was.

It is claimed that soap nuts are a general cleaning detergent and not that they remove stains. The items used for the general detergency swatch can be considered stains and not general dirtiness.

Those in the soap nut industry refute these claims and note the following weaknesses of this test:

“They strongly focused on stains, not the general cleaning capacity of soap nuts.
The category for ‘general cleaning’ tested 3 types of ‘dirt’, but 2 of them were actually stains. General cleaning was regarded as milk, nut oil and an unspecified pigment dye. Oil and colour dye cannot be considered general dirt. Even chemical detergents will struggle to remove oil and dye stains. This was really disappointing from Choice.
The way they test is with pre-stained test strips imported from the Netherlands. They attach these test strips to some fabric and throw them in the wash. Everybody knows that the longer stains are left on clothing, the harder they are to get out. I don’t think many of us get our clothes dirty and stained, leave them TO SET for a few months, and then ship them across the world to be washed”

Clean Cloth Nappies Down Under, which uses Fluff Love University’s science-based laundry methods to test detergents, also does not recommend using soap nuts in its Detergent Index. This relates to soiling and not to general cleaning.

A study by Anke Kruschwitz, Aline Augsburg and Rainer Stamminger found that at 30°C, stain monitors showed some cleaning effect on all stains for all treatments where detergent is added, but no effect when soap nuts and wash balls were used. For this study, a 60°C program was also tested and the results were similar. The study concludes that “soap nuts and all kinds of wash balls do not show a significant difference in cleaning performance compared to the treatment in pure water”. The full study can be found here.

So, according to these studies, they don’t do anything and if clothes are getting cleaner when they are used, plain water and machine agitation are cleaning the clothes, not the soap nuts; however, this is strongly disputed by the soap nut industry for the reasons mentioned above, especially their focus on stains rather than general cleaning, and questioned by those who swear by using soap nuts.

There is also the argument that their increase in popularity in Western countries has upped their price in India, where they have been used to clean clothes for centuries, meaning they are no longer affordable for those who used to use them and their use is being replaced by cheaper chemical solutions, which are polluting the river water, as they wash their clothes in the river.

In addition, all soap nuts are imported into Australia. So, that is something else to take into consideration.

CONCLUSION: Do soap nuts work?

While, some scientific studies have found that they don’t work and you get the same effect with plain water, the way the testing was done for these studies was not perfect and is questioned by some, who specifically argue that they show that soap nuts don’t remove stains and that they don’t show that they aren’t effective as a general detergent.

It is openly acknowledged by the soap nut industry that soap nuts are not as effective on stains as chemical detergents, but they maintain that “based on our experience and countless other people’s opinions from around the world, Sapindus Mukorossi soap nuts are excellent for general laundry needs, multi-purpose cleaning, personal care, and various other uses”.

They suggest doing your own test by handwashing a dirty cotton face mask or cotton T-shirt in water first, followed by a handwashing it in soapnut liquid.

If you do decide to use them, see the advice by those who do use them above and follow it for the best results. Let us know how you go! They are not expensive and can be bought in bulk at certain stores, so you can buy a few to try out without committing to a huge bag.

There are other eco-friendly laundry powder options. You can buy it in cardboard boxes without any plastic, so while, this isn’t waste free, it is a plastic-free option. You can also buy washing powder in bulk using your own container at certain bulk stores.

Another option is to make your own washing powder. You’ll find lots of recipes online. However, Butter Believer warns against making your own detergent, as you can’t create the type of surfactants needed for a detergent to work at home in your kitchen and washing machines are designed to work with detergents not soap, so they are generally not good for your machine or your clothes. Read more on this here.

For more on zero waste laundry and to learn what can we do on a personal level to reduce the amount of microfibres our clothes shed, read our Preventing Microfibres From Flowing Any Further post.

For this article, the information was obtained from zero wasters in Facebook groups like Zero Waste Victoria and the following links:

Waste-Free Laundry: Do Soap Nuts Work?