When he wasn’t busy wrapping buildings and bridges in vast reams of fabric, Christo was wrapping absolutely nothing. The Bulgarian artist made his name – alongside his partner Jeanne-Claude – with a wrapped Reichstag, a swaddled Arc de Triomphe and an enveloped Pont Neuf. They found a way of containing, embracing, protecting and smothering the whole world. But in the 1960s, he was trying to wrap air. Nothing more.

Christo (Jeanne-Claude hadn’t been given full joint credit at this point) wanted to contain the air within a room, but the original idea was limited by technical constraints. Now, 50 years after it was first proposed for the Institute of Contemporary Art in Philadelphia, and six years after Christo’s death in 2020, he’s finally pulled it off. The opening room at Gagosian has been bisected horizontally, a huge polyethylene sack splitting the room in two, held to the ceiling by white ropes. It droops low, sinking into the middle of the space, forcing you to crouch to get under it. You’re forced into a physical relationship with the work, bullied into changing how you interact with the environment.

The space is still functionally, realistically, empty – there’s nothing up there but air. But now that air has been made physical. It has a visible presence.

The amazing trick of this work isn’t just making air into something tangible, it’s giving it a sense of weight. The plastic sack sags, bulges bulbously against the ropes. It hangs down into the space, presses itself heavily into the room. It looks like flesh that can’t be contained by clothes, love handles bursting over a too-tight waistband. How amazing is that? Making air visible, physical, heavy.

It’s not the only time Christo worked with air. He spent the 60s making wrapped bubble works, trying to contain the uncontainable. Photos in a vitrine show a work for Documenta in 1968: a giant polyethylene tube they could barely erect. It’s shown flapping about flaccidly before the US Air Force showed up and got it standing to full attention. It’s ridiculously, hilariously phallic, a superhuman boner of air and plastic reaching to the heavens in a German park. It makes the bodily implications of the main work all the more apparent: it’s not just air made visible, it’s air made flesh, bound by rope. Christo, you old dog.

In the last room, an old Volvo belonging to one of his art dealer mates has been wrapped in a sheet. The dealer had bought a new motor but was too attached to the old one to let it go to the scrapyard. Christo’s intervention is an act of conservation. He has preserved this car’s past life, saved all the memories worn into its leather, metal and rubber for eternity. It sits here as a monument to its own past.

Christo’s work is a funny mixture of profound and ridiculous. The car is just a Volvo in a sheet. The main installation looks like Gagosian got some dodgy builders in and they couldn’t be arsed to tidy up. But then the works trigger all these thoughts of space and weight, bodies and intimacy, history and memory. You think about your body in this room, the air that you’re breathing, the hours someone spent in that car driving down a motorway to see their family or go to the seaside, and wow, all of sudden you feel a bit emotional. And all Christo needed to achieve that effect was some ropes, a sheet and a really, really big plastic bag.

• Christo: Air is at Gagosian, Grosvenor Hill, London, until 21 August