'Pee-back time' for drunken behaviour

If you're on a night out in Germany, you might want to think twice before relieving yourself on the streets.

Fed up with drunks using buildings in the party district of St Pauli in Hamburg as a toilet, a community group is getting its revenge.

Walls have been coated with water-repellent paint which causes "splash-back", so anyone who urinates against them will get an unexpected, ahem, taste of their own medicine.

This graphic shows how the paint works and causes splash-back
Image caption The paint uses nanotechnology to create "splash-back"

It's being called "pee-back" time.

The paint, called Ultra-Ever Dry, uses nanotechnology to cover a surface and create a barrier of air. The maker's website says it will "completely repel almost any liquid."

A sign saying "Do not pee here. We pee back."
Image caption The community group say it's about educating tourists

The paint, called Ultra-Ever Dry, uses nanotechnology to cover a surface and create a barrier of air. The maker's website says it will "completely repel almost any liquid."

Julia Staron, from IG St Pauli, the community group behind the idea, told Newsbeat the paint is usually used on boats and aircraft, but with 20 million tourists coming to the district every year, and drinking a lot, another use has been found for it.

The party district of St Pauli
Image caption St Pauli attracts 20 million tourists every year

Julia says the paint seems to be working and, "the problem has finally got the attention it deserves."

So far only two buildings have been treated, but there are plans to paint more in the next couple of weeks.

It's not the first time so-called "hostile architecture" has been used to change people's behaviour.

You might remember the row that started when metal spikes appeared outside some buildings in London to stop homeless people sleeping there.

Other examples include studs on low window ledges to prevent sitting, and slanting seats at bus stops to put you off hanging out there for too long.

Armrests on public benches are also designed to stop people sleeping on them.

A bench with arm rests dividing it to stop people sleeping
Image caption Armrests deter people sleeping on this bench

Metal wedges called 'pigs' ears' or 'skate stoppers' on benches and ledges are designed to stop skaters using them as ramps.

The practice can also extend to sound deterrents called "Mosquito" devices which emit an annoying high pitch sound only audible to teenagers, to stop them loitering in certain places.

As for the idea of "splash-back" paint, Julia Staron told Newsbeat, she thinks it will catch on.