Is sunning out stains ever okay? ☀️

Most people are either in the camp of “the sun removes all stains” or say that “sunning out stains never actually works.” None of them are entirely right, and being dogmatic about this undercuts people’s real-life experiences. So let’s talk about what really happens when you try to sun out stains, and whether there are times when this is a legitimate stain-removal option.

The critical point is determining the difference between embedded soiling and cosmetic stains. When it comes to sunning:
❌ soiling
✅ stains

Knowing the difference between what is soiling and what is staining can be tricky, especially as the two words are often used interchangeably. 

In laundry, soiling is something that can be physically removed by scraping off with a brush or being washed away during the wash cycle. Staining is an area of discolouration that remains after washing even when soiling has been removed.

Getting to know poo 💩 

The most vibrant stains in cloth nappies come from poo. Different foods and different stages of your baby’s development alter its colour and texture. You’ll notice their poo change from newborn meconium black to mustard yellow, then to shades of brown. 

In an ideal world, all poo stains at every stage of your baby’s life would vanish after a two-step warm/hot wash routine with a quality detergent. However, even with the best wash routine, some pigment occasionally remains, even when all physical poo particles have been washed away.

What makes poo stainy

Poo consists of water, solids and a tiny amount of bile and undigested plant pigments. It is the bile and pigments that cause stains. 

Brightly coloured fruits, vegetables and spices contain more pigments:

• Anthocyanins (blueberries, blackberries, strawberries, raspberries and red cabbages)
• Beta-carotene (carrots, pumpkin and sweet potato)
• Carotenoids (oranges and watermelon)
• Chlorophyll (leafy greens)
• Cocoa tannins (chocolate)
• Curcumin (turmeric)
• Betalains (beetroot and dragon fruit)
• Lycopene (tomatoes and tomato sauce)

If you are breastfeeding, your baby’s poo will also include pigments from your diet (passed through your milk).

Baby, especially newborn, poo contain higher levels of bilirubin. Bilirubin is a yellow-orange compound that is a natural byproduct of broken-down red blood cells. As your newborn’s developing liver and intestinal tract are not mature enough to fully process bilirubin yet, it is excreted with your baby’s poo.

Together, these concentrated pigments can leave behind stubborn cosmetic stains on your nappies, even with a great wash routine.

Removing stains with your wash routine 

Before you consider sunning out leftover stains, you need to make sure your wash routine is as effective as possible. Most stains, including vibrant pigments in newborn poo, can be removed with an effective wash routine. 

The impact of detergent quality

Although stains can happen with premium detergents, they are more likely to appear with lower-priced ones and ones that market themselves as ‘gentle’ or ‘eco friendly’. By design, non-premium formulas have fewer active ingredients, which means less stain-removal power. 

Weaker formulations also struggle to remove embedded soiling. If you notice frequent stains, especially stains that cover a large surface area, it is important to increase the cleaning factors through longer, hotter cycles; a different detergent; or adding a laundry booster or chlorine bleach. 

In some parts of the cloth nappy internet, a standard routine consists of a cool rinse followed by a lukewarm wash with a teaspoon of detergent. These routines do not effectively remove soiling or staining, and result in nappies that have large visible yellow and orange marks. 

If you have persistent staining like this, the sun is not the answer. Make a post in our Facebook group and we can help you improve your washing routine. ♥️

Photodegradation: the science behind the sun

When you hang stained nappies or clothes in the sun, it triggers a reaction called photodegradation. 

The pigments in bile and plant matter have sensitive molecular structures that absorb light, making stains visible. Sunlight contains high-energy ultraviolet (UV) radiation that breaks the chemical bonds within these molecules. With sun exposure, the pigment breaks down into smaller, colourless compounds. Once those bonds are broken, the molecule can no longer hold onto its colour and the stain fades from view. 

We see the same mechanism when the sun sun-bleaches our hair, degrades outdoor furniture, or fades clothing and fabric. 

It’s important to remember that photodegradation is a chemical reaction that breaks things down, rather than a physical cleaning process. Just like the faded cap pictured below, the sun hasn’t ‘cleaned’ the fabric; it has simply destroyed the dye’s chemical bonds and faded the colour where it was exposed.

Won’t the stain ‘come back’? 🧟

One thing you might hear is that sun-faded stains come back. This is a misunderstanding of photodegradation, and misses the point about differentiating between staining and soiling.

If nappies or clothes are put in storage looking clean and develop yellow marks over time, this isn’t because the stains returned. It’s because the items weren’t completely clean in the first place. The appearance of new marks means there was residual soiling buried deep within the fibres that continued to oxidise while the items were in storage.

Spit-up on newborn clothes, especially around the neckline, is a common source of these delayed marks. Breastmilk and infant formula are inherently fatty, and the spit-up requires a thorough washing process to remove. Either manual pretreatment or double washing is often needed to remove the hidden soiling trapped deep within the fibres. Consequently, these ‘zombie marks’ frequently appear on items washed prior to adopting your Clean Cloth Nappies routine. 

Before you sun

If your nappy or clothing is physically clean, free of trapped soiling, and smells completely fresh straight out of the washing machine, don’t be too hung up on using the sun for some added stain removal.

Before you do, run through this quick checklist to ensure you are actually dealing with a cosmetic stain:

• Was the wash routine adequate? Use an appropriate dose of quality detergent, a solid two-step wash routine, and warm to hot water.
• Does it smell fresh? The item should have absolutely no lingering poo, barnyard, or ammonia smell out of the washing machine.
• Is all physical soiling gone? The fabric must be entirely free of trapped poo, vomit, spit-up, food, dirt and grease.
• Is it just a shadow? The remaining mark should purely be a flat discolouration (leftover pigment), not a crusty, slimy, or raised patch of fabric.

If you can confidently answer ‘yes’ to all of the above, the stains you have are purely cosmetic. All the physical soiling has been removed and only pigment remains. 

The golden rule of sunning 🌞

Always ensure your wash routine has done the heavy lifting first. As long as you have washed away the embedded soiling and are only dealing with a harmless cosmetic stain, don’t be too hung up on what you hang out in the sun.

However, sunlight is never a replacement for a good wash routine, and it is always our last resort for nappies.