Ballpoint Pens
The first ball pen was invented in 1888, but it wasn't until the 1940s that Laszlo Biro began to develop what was to become the first commercially successful version. Ball pens use a viscous oil based ink which is fed to the ball by gravity and capillary action. Paul C Fisher developed the ball pen further by using a pressurised refill and a very thick ink. The Fisher Space Pen doesn't use gravity and can write upside down, in space and under water!
