Testing is actually done on painted plates (yellow) rather than miniature cars

Testing is actually done on painted plates (yellow) rather than miniature cars

A miniature car wash, about the size and shape of a popcorn machine, plays an important role at the Nissan Technical Center North America in Michigan.

Equipped with a spinning brush that has vibrant blue bristles, this highly specialised machine allows engineers to test paint samples to make sure exterior paints hold up to the tough environment of automatic car washes.

To mimic an automatic wash cycle, which can scratch clearcoats and abrade paint, the miniature car wash spins the brush at around 180 rpm, causing the bristles to harshly slap the paint sample as water jets spray and special dirt, called 'Arizona test dirt' by testers, is applied to paint samples during the test cycle to replicate real world grit and ensure that paint is tough and long-lasting.

Though pictures show miniature cars, in actual testing, paint is applied to rectangular plates (such as the yellow sample seen in the photos), which are placed into the miniature car wash and tested multiple times to ensure a top quality finish that lasts.