The exact composition of the STF is known only to Moratex and its inventors at the Military Institute of Armament Technology in Warsaw, but ballistic tests proved its resistance to a wide range of projectiles.
"We needed to find, design a liquid that functions both with projectiles hitting at the velocity of 450 meters per second and higher. We have succeeded," said Deputy Director for Research at the Moratex institute, Marcin Struszczyk.
Struszczyk said the liquid's stopping capability, combined with the lower indentation of its surface, provides a higher safety level for the user compared with traditional, mostly Kevlar-based, solutions.
"If a protective vest is fitted to the body, then a four centimeter deep deflection may cause injury to the sternum, sternum fracture, myocardial infarction, lethal damage to the spleen," Struszczyk said.
"Thanks to the properties of the liquid, thanks to the proper formation of the insert, we eliminate one hundred percent of this threat because we have reduced the deflection from four centimeters to one centimeter."
SF fans of course remember the Flexible Armor Suit from the 1966 novella Neutron Star by Larry Niven.
He was weaponless, but his suit was a kind of defense. No projectile short of a fast meteorite could harm him. Like a silicone plastic, the pressure suit was soft and malleable under gentle pressures, such as walking, but instantly became rigid all over when something struck it...
Seabreacher, H.G. Winter's 1939 Torpoon
'Ken lay full-length in the padded body compartment, his feet resting on the controlling bars of the directional planes, hands on the torpoon's engine levers.' - HG Winters, 1939.