Driven by TikTok tutorials and the DIY boom through lockdown, the trend for expanding foam decor has taken off, at the expense of an independent Danish designer.

You might have seen it seeping out from the corner of an influencer’s mirror selfie on Instagram, likened to popcorn, marshmallows or clouds. The latest social-media-driven decor trend is in fact expanding polyurethane-based builder’s foam, available from any hardware shop.

In recent months it has gone from insulation to interior design, sprayed around mirrors – and either painted in pastel or neon, or left to assume its natural yellowish hue – to create a statement frame for selfies.

These “foam mirrors” have exploded across social media – first on design blogs as an aspirational objet, then as a craft project as people set out to make their own. According to Google Trends, global search interest in foam mirrors coincided with the DIY boom through lockdown.

“It was definitely a perfect storm,” says Lillian Ahenkan, a Sydney-based podcaster and entrepreneur, popular on Instagram (as @flex.mami) for her DIY approach to decor. She posted perhaps the first “DIY spray foam mirror” tutorial back in January.

“It wasn’t well received when I made it,” she says. “The comments are like: ‘it looks like intestines’, ‘it looks like guts’.” Ahenkan was not put off, describing the result as “jolie-laide”: “I made it to make my house look cute.”

In sharing her process – later covered by design blogs – she no doubt contributed to foam mirrors’ outwards spiral. “Up until then it was a cool thing to be retweeted.”

In April the model Mathilde Gøhler shared her own “little DIY project” with her 1.1 million followers on Instagram – just after the influencer Maria Kragmann started shooting her outfit photos in a mirror she described with the popcorn emoji.

Caitlin Stockton, of Leeds, was inspired to make her own a few weeks later, applying 151 Gorilla Filler to a mirrored wardrobe door she’d found in her loft. She was pleased with the result but says she “probably wouldn’t have bothered if it wasn’t for lockdown”.

TikTok has also been instrumental in driving the trend, with 15m views to videos tagged #foammirror, many of them tutorials. “I couldn’t actually avoid it – the foam mirror trend was everywhere,” says Elle Adams, a London-based YouTuber who vlogs as The Elle Next Door.

“But I loved how it looked and was so intrigued that I couldn’t stop watching.” Adams made her own mirror back in May (and her own mirror how-to, which has since amassed 50,000 views).

Using spray foam is generally considered safe, though protective clothing and goggles and ventilation are advised. Adams says it was an “incredibly easy” DIY task – “the fact that I managed to pull it off says it all” – but striking in its divisiveness.

“People are quite vocal in their hatred of it … but months on, I still genuinely love it.” Whatever you make of the result, with filler costing less than £10, it is low-cost, but high-impact.

Leon Pullin and his girlfriend Lucy Brooksbank, of Barnes, west London, made their foam mirror during lockdown after seeing the Swedish designer Gustaf Westman’s similar-looking “popcorn” sideboard online. Those retail for thousands of pounds, says Pullin: “We thought we would have a go at home for fun.”

Described as “the popular kid of Instagram design”, Westman is part of a broader move away from minimalist interiors, arguably driven by social media.

But in the spread of foam mirrors across the internet, one name has been buried by the hype: that of Anna Louise Kragelund, the independent Danish designer credited with creating them.

As Studio Anna Thoma, Kragelund’s custom-made mirrors cost around 10,000 kroner (£1,200), though she only ships within Scandinavia. “I hadn’t thought about it at all becoming a trend, that it would be a DIY,” she says.

Kragelund first exhibited mirrors upcycled with expanding foam at a design fair in Copenhagen early last year, generating online buzz that “Danish design is cool again”.

She was later commissioned to make a large-scale mirror, in millennial pink, for the shopping centre Magasin du Nord. “Then all the bloggers and Instagrammers started showing up,” Kragelund says – and posted photos of themselves reflected in her creation.

One selfie posted by the Danish fashion influencer Anne Johannsen inspired a glut of tutorials, including Ahenkan’s. Kragelund admits she panicked at first to see reports of the “foam mirror flourishing all over Instagram”: But she has come to view the imitation as flattery, she says. “It would be different if it were a big company copying my mirrors rather than the girl next door making her own.”

Ahenkan points out that beneath the “avalanche” of expanding foam were people inspired to attempt DIY, perhaps for the first time. “That was exciting to see,” she says. “The next step is encouraging people to actually conceptualise things from their mind.”