It’s a powerful pen. Its influence reaches beyond the school classroom. We use red ink for all kinds of corrections ...

It marks the origin of the pen knife. Before 1850, the process for vulcanization of rubber had not been discovered, and the only way to correct a writing mistake was to scratch the ink off the ...

Within the colours of visible light, red is the longest wavelength ... we can compare them to ordinary ballpoint pens. When light hits the ink of a blue pen, the ink reflects blue light and ...