Updated

Scientists in Poland are working on body armor technology that uses specially-designed liquid to protect against bullets, according to Reuters.

Unlike Newtonian liquids such as water, the Shear-Thickening Fluid (STF) hardens on impact from a projectile, the report says, offering protection from bullets.

The technology has already been touted as a potential replacement for Kevlar in body armor.

Reuters says that the exact composition of the fluid is known only to Poland’s Institute of Security Technologies, known as Moratex, and inventors at the Military Institute of Armament Technology in Warsaw.

Popular Science notes that, with STF (also known as ooblek), a bullet’s force is absorbed by the liquid, and then dissipated outwards through the fluid.  STF, which has been described as “bulletproof custard,” consists of hard nanoparticles suspended in a liquid that turns rigid when struck by a projectile.

The Polish scientists are not the first to work in this space – defense giant BAE Systems has worked on body armor that combines STF and Kevlar, according to Popular Science, while the U.S. Army Research Lab has conducted liquid body armor research with the University of Delaware.