Think ink!

Writing with ink requires using a pen or brush. The earliest pens were probably pointed sticks or the like dipped into ink. People gradually learned how to make a pen that could hold more ink so it didn't have to be dipped so often. They would sharpen the point of a bird's feather and cut a shallow trough to hold the ink. The Romans made pens from the stems of marsh grasses, including bamboo. The tubelike stems could hold a small amount of ink, and the end could be cut to a point to make a finer line. Squeezing the reed forced ink in the stem to flow to the nib. It was the earliest kind of fountain pen, perhaps.

For more than 1,000 years, beginning around AD 700, the quill pen was the favored writing instrument. The finest ones were (and still are) made from one of the five flight feathers from the left wing of a domesticated goose. Swan feathers were more expensive because they were harder to get. Crow feathers were good for making fine lines. Quill pens must be resharpened often, using a special knife - a pen knife, in fact. A quill pen lasted about a week.

Inventors tried to make more durable pens that could hold more ink. The oldest known example of a pen with an ink reservoir (an early fountain pen) was created by Frenchman M. Bion about 1702. Early fountain pens were prone to spills and breakdowns.

An American 19th-century insurance salesman named Lewis Waterman became determined to improve the fountain pen when a leaky pen ruined an important sales contract. He added an air hole in the nib and put grooves inside the mechanism that moved the ink to the point. He patented the pen in 1884.

19th-century American inventor Thomas Edison also focused some of his creative energy on writing instruments. He developed an electric pen, an early example of a copy machine. At that time, if people wanted a copy of a document, they had to recopy it by hand. Stencil copying was also an option. First a drawing or manuscript was made by making tiny pinpricks through a piece of paper. Ink was pressed through the holes in the paper onto a paper underneath to make an image. Several copies could be made from one stencil.

Edison's electric pen had a battery-powered motor to move a sharp stylus up and down through a hollow tube. A writer could guide the pen to form letters for a stencil at high speed. About 60,000 electric pens were sold, but other stencilmaking technologies evolved that were less expensive. The typewriter - and the carbon copy - made stencils obsolete in the 20th century.

Ink, on the other hand, is far from obsolete. As mechanical copying and printing became more popular, new inks were developed. A special green ink was invented in 1857 by American chemist Thomas Sterry Hunt. It resisted attack by acids, bases, and other chemicals. It couldn't be reproduced accurately in a photograph - and so was used to print US currency.

Printing ink is greasier than ink used for writing. Printer's inks are designed to work with specific kinds of printing equipment to form the clearest image without accumulating in the machinery.

Now you can walk in a store and choose from a rainbow of inks in pens of all shapes and sizes. They may not improve the quality of what you write, but they do make it easy and fun.

• To learn how to make your own "invisible ink," visit chemistry.about.com.

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