Drying Nappies in Wet Weather

Here in South-East Queensland the wet weather is brewing, which is wonderful for the garden but a bit tricky on the nappy drying front! If you have a smaller stash of nappies or you have nappies such as All-In-Ones that are slow to dry, then you may run into issues when the rain sets in. A clothes dryer is an obvious solution,  but not everybody owns or uses a dryer and for many families, keeping their electricity usage low is part of the waste-minimisation ethos that they apply to their lives.

In this blog I bring you a little science so that you can apply the principles of evaporation (aka drying) to your laundry during wet weather.

Evaporation is driven by
1. Solar Radiation/Heat Source
2. Vapour Pressure Deficit
3. Wind Speed

Solar Radiation is energy provided by the sun. Higher Solar Radiation = more energy for drying = faster drying. You would have already observed this when your clothes dry quickly in summer compared to winter. When you use a clothes dryer, or your hair dryer, the heater element provides the Radiation (heat). Higher temp = faster drying, just like on a hot day.

Vapour Pressure Deficit is the difference between the humidity of the air and the amount of moisture that the air can hold when it is saturated. This is similar to "relative humidity" but is not dependent on temperature. A larger value of Vapor Pressure Deficit (corresponding to lower humidity) will facilitate higher drying speed. A nice example of this is hanging out your laundry on a really dry day- it dries really quickly! When you hang out your nappies on a humid day, they dry more slowly, as the Vapour Pressure Deficit is low.  Higher Vapour Pressure Deficit = Low Humidity = Faster Drying. When it's raining, the humidity of the air is 100%, so there is no Vapour Pressure Deficit to drive evaporation and dry your laundry. You can dry your laundry faster by putting it somewhere that the air has lower humidity than out in the rain. Air conditioned spaces are one example, or even just indoors if your house isn't as drafty as my timber abode.

Wind Speed is the third factor that influences evaporation rate. As the wind blows, it blows away tiny water particles that are on the surface of whatever item is wet eg. your nappies, meaning that the humidity is reduced, Vapour Pressure Deficit is increased and faster drying occurs. You can generate faster Wind Speed by drying your laundry on a clothes airer in front of a pedestal fan or under a ceiling fan.

So there you have it! High incoming Radiation, high Vapour Pressure Deficit and High Wind Speed combine to dry your laundry super quickly. When it's raining and you need to dry your laundry, your best bet is to dry it somewhere warm and dry in front of a fan. It may not dry as quickly as on that hot summer day but it will be much faster than not drying at all!