Does the Moon Really Whiten Laundry?
In days gone by, our grandmothers would hang out their laundry on full moon nights, convinced that it helped remove stains. For centuries, this celestial body has fuelled beliefs and legends, from werewolves to early births, and even a supposed influence on hair growth. But what is the truth about its effect on laundry? Does the Moon really have bleaching powers? Does it fade colours? Is it wise to dry your washing outdoors during full moon nights? Embrin unravels fact from fiction regarding this mysterious lunar influence.
Morning dew: a natural bleaching agent
A quick science note: morning dew contains peroxides. These are formed from the dissolution of ozone, which itself results from the chemical reaction that occurs when sunlight interacts with molecules in the earth’s soil.
Peroxide, for its part, is always a natural bleaching agent. It’s used in many cleaning products, as well as in substances that allow us to lighten unwanted body hair, for example—yes, really! Some even claim that peroxide also fades car paintwork!
Is the Moon responsible for this bleaching?
In truth, the Moon has no direct link with the bleaching observed, though there may be an indirect effect related to atmospheric conditions. Moonlight is especially visible when the sky is clear, which often coincides with nights when dew is most abundant. This nocturnal moisture settles on laundry, encouraging a natural chemical reaction involving water, oxygen, and sometimes traces of peroxide naturally present in the environment.
When the Sun rises after a night of heavy dew, its rays intensify these reactions on the fibres, gradually increasing the bleaching effect. This phenomenon becomes particularly noticeable over the years, explaining why our ancestors made a connection between the Moon and these changes. Furthermore, the cycles of the new moon and full moon influence tides and air humidity, which could indirectly affect dew formation.
Visible moon = Clear sky = Lots of dew = Significant bleaching
But in fact, it is only the dew that is responsible for this bleaching. So, it is incorrect to say that moonlight strictly speaking bleaches laundry. The lunar cycle that gives rise to the full moon and new moon, therefore, has no effect on laundry by extension.
How should you dry your linen laundry?
To preserve the vibrancy of colours, it is advisable to dry your laundry away from morning dew, as well as from direct sunlight. Ideally, you should dry it under shelter outdoors or in a utility room: in a covered space that is protected from the elements.
For public health reasons, it is not recommended to dry laundry inside the home, particularly in living areas. This encourages humidity, which can be harmful for people with asthma or lung conditions.
That said, there are alternatives for every situation:
- if you have no outdoor shelter, hang your laundry out when the sun is not at its strongest and bring it in before nightfall to avoid it being left out overnight and exposed to dew;
- if you have no outdoor space, you can hang your laundry indoors using a dehumidifier to absorb the moisture produced. In the height of summer, you can also leave all the windows open to allow humidity to evaporate naturally.
Finally, if you have a tumble dryer, its use is perfectly recommended, provided you select the programme suitable for delicate fabrics.
