Bizarre chalk hack claiming to prevent moisture and mould divides online: ‘Absolutely dry’

An unusual hack is garnering viral attention online for its claim to prevent moisture and mould in the home – and all you’ll need is a piece of chalk. In a recent post in the Australian Facebook group ‘Mums on a budget’, one of more than 145,000 members shared her discovery of the trick that allegedly fixed her condensation problem at home.

In the post, the mum shared a photo of a large piece of chalk on her window sill, claiming that it was a “hack for those who struggled with moisture on the windows”.

“Every morning we woke up and the bedroom windows had condensation on them,” she wrote in the post. “And in the long term it’ll probably turn into mould. So I tried. For the last three mornings our windows have been dry. Absolutely dry.”

She continued to explain that the hack had worked in two bedrooms and one bathroom, with only one piece of chalk needed for three large glass windows.

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“I don’t know how long the chalk will be good for but certainly cheaper than getting a dehumidifier or the moisture absorbing stuff,” the mother added. “Hope this helps someone else too! Also if you have only coloured (chalk), maybe put a plate or bowl under it just in case.”

Chalk hack divides internet

The post stirred a flurry of comments from other mums who were eager to try the hack for themselves.

“Great idea,” one member wrote. “I can only imagine that you can reuse and leave the chalk in the sun to dry out each day.”

“Apparently this will do the trick – place the chalk on window sills or other areas that are affected by condensation, and it will help to soak up moisture in the air,” another explained.

“Just Googled and apparently rock salt is even better,” a third added.

“I’m just trying this now – two days with the chalk on the sill, window dry,” another member wrote. “Day three, windows wet. So I’m thinking I need to replace the chalk every second day and air out the old chalk in the sun to dry it.”

A fellow commenter said that had tried a similar technique of placing a stick of chalk in clothes drawers to avoid any mould build-up on clothing.

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However there were also others who had tried the hack for themselves and were less impressed.

“Saw this last week and tried it,” one commenter wrote. “100% does not work.”

“Didn’t work for me,” echoed another.

Mould specialist weighs in on chalk debate

Certified indoor environmental consultant and managing director of mould removal service Mould Rescue, Penny Tralau explained to Yahoo Lifestyle Australia that the chalk hack, or similar hacks using vinegar, clove oil or rock salt, did not work as well as claimed.

“People are just convincing themselves, it’s the same reason that everyone on the internet thinks that vinegar is a solution,” Tralau said. “Mould is microscopic as well, so just because you think it’s gone doesn’t mean it’s gone, and non-viable mould spores are more toxic than even live mould spores.”

She added that the temperature of a surface was directly relevant to the dew point overnight, when vapour turns into liquid, and that single-glazed windows would always condensate unless a dehumidifier was in place.

“And if it’s condensating on windows, it’s going to be condensating on other parts that you aren’t aware of, like a chest of drawers,” Tralau said. “A home is like a human, it has to breathe all the time.”

She noted that implementing a dehumidifier or leaving windows slightly open overnight would help to prevent excess moisture far better than a piece of chalk.

Try it for yourself – but this hack might be best left on the internet, after all.

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