The problem with ‘sunning out’ stains

‘Sunning out’ stains is often suggested as a laundry hack on social media and blogs. They spruik sunlight as an affordable, effortless way to remove stains from cloth nappies and clothes. Some even suggest squeezing lemon juice onto wet nappies to aid stain removal. The problem with sunning out stains is that it does not actually produce clean laundry.

Drying laundry in the sunshine is totally fine! It’s only putting laundry in the sun to fade stains, rather than removing them through good laundry practice that’s the issue.

~ Laura, Australia

Sunlight does not clean your nappies

While sunlight can fade the appearance of stubborn stains in the short term, it is not a substitute for a decent wash routine. Sunning fades surface stains, whilst soiling embedded in the fibres remains. Marks that are sunned out reappear over time, such as when garments are stored and then removed from storage for a younger sibling.

Volatile gases like petrol, diesel or perfumes will dissipate in fresh air. However, hanging smelly nappies outside only lessens their odour; it does not get them clean.

Items should come out of the washing machine with no stains and no smells. If your laundry regularly has stains or smells, it is time to revisit the four cleaning factors: time, temperature, chemicals and mechanical action (agitation).

The right balance of cleaning factors will give you clean, fresh, stain-free laundry every time, regardless of the weather.

The difference between stains and soiling

Telling a stain apart from soiling takes an understanding of laundry science. Our goal is to educate people on the difference and make sure they are not attempting to ‘sun out’ embedded poo, vomit, food or dirt.

We often use the words ‘stains’ and ‘soiling’ interchangeably, in reality, they are two different things.

Soiling is something you can scrape off physically with a brush or that is physically washed away during the wash cycle. The most common soiling on cloth nappies is poo. Common soiling on household laundry includes food particles, baby spit-up (vomit), dirt and mud.

Staining is an area of discolouration that remains after washing even when soiling has been removed. Residual food stains (such as tomato sauce) on clothing, or sorbitol stains on nappies, are oxidisable stains. They are caused by leftover pigment.

Some fruits and vegetables stain, such as blueberries, watermelon, strawberries, bananas, carrots, and tomatoes. Exclusively breastfed (EBF) baby poo can also stain.

Stains from leftover pigment are predominantly cosmetic and do not always mean the item is dirty.

Before attempting to sun out stains, ask yourself if the marks are most likely to be a stain or soiling. Common examples of embedded soiling are poo in multilayered inserts or saliva and spit up in the neckline of baby clothes.

Pigment in poo

Faeces (poo) is made up of water, dead bacteria, indigestible food and other molecules. In some cases, this includes small amounts of pigment. The pigment itself is not dirty; however, that is only a tiny component of the faecal matter. This means the vast majority poo ‘stains’ are small poo particles that have not washed out properly.

Normally, feces are made up of 75 percent water and 25 percent solid matter. About 30 percent of the solid matter consists of dead bacteria; about 30 percent consists of indigestible food matter such as cellulose; 10 to 20 percent is cholesterol and other fats; 10 to 20 percent is inorganic substances such as calcium phosphate and iron phosphate; and 2 to 3 percent is protein.

~ Encyclopedia Britannica

Sunning out tomato stains

Tomato stains are caused by lycopene, which breaks down quickly in UV light, so sunning out a pigment from something like tomato sauce is effective. However, it will not remove any lingering soiling (grease or other food particles).

Does the sun or ultraviolet light sanitise?

The answer is: sometimes, in certain situations, but none apply to nappies or textiles.

Sunlight consists of electromagnetic radiation in the visible light, ultraviolet (UV) light and infrared radiation ranges of the electromagnetic spectrum.

Solar water disinfection 

UV light and heat from the sun are used to purify drinking water in polyethylene terephthalate (PET) plastic bottles. This method is called solar water disinfection, or SODIS.

Water poured into clear or blue polyethylene terephthalate water bottles (glass bottles also can be used) is exposed to sunlight for at least 6 hours, or up to 48 hours in cloudy weather. The heat and ultraviolet radiation of the sunlight kill bacteria and protozoan parasites and inactivate assorted viruses. 

~ National Center for Biotechnology Information

Ultraviolet Germicidal Irradiation

UV light consists of three different wavelengths: UVA, UVB and UVC. UVC is used in a sanitising method called Ultraviolet Germicidal Irradiation (UVGI). However, UVC is blocked by the ozone layer, and does not reach the Earth’s surface. 

Sunscreens only contain UVA and UVB filters because UVC is blocked by the Earth’s atmosphere.

The most effective, economical and readily available options for sanitising nappies and textiles are chlorine bleach or a 90/95°C sanitise cycle.

Embrace the sun’s power to dry your nappies and textiles, but focus your stain-removal efforts on the laundry.