Nibs
The modern fountain pen nib may be traced back to the original gold nib which had a tiny fragment of ruby attached to form the wear-point. Following the discovery of the Platinum group of metals which include ruthenium, palladium, osmium and iridium, a small quantity of iridium was isolated and used on the iridium-tipped gold dip pen nibs of the 1830s. Today, nibs are usually made of stainless steel or gold alloys, with the most popular gold content being 14 carat (58⅓%) and 18 carat (75%). Gold is considered the optimum metal for its flexibility and its resistance to corrosion, although gold's corrosion resistance is less of an issue than in the past because of better stainless steel alloys and less corrosive inks. Gold nibs are tipped with a hard, wear-resistant alloy that typically uses metals from the platinum group. The tipping material is often called "iridium", but there are few, if any, penmakers that still use tipping alloys containing the metal. Steel nibs may also have harder tips; those with un-tipped steel points will wear more rapidly due to abrasion by the paper.
The nib usually has a slit cut down its centre, to convey the ink down the nib by capillary action, as well as a "breather hole" of varying shape to promote the exchange of air for ink in the pen's reservoir. The breather hole also acts as a stress relieving point, preventing the nib from cracking longitudinally from the end of the slit as a result of repeated flexing during use. The whole nib narrows to a point where the ink is transferred to the paper. Broad calligraphy pens may have several slits in the nib to increase ink flow and help distribute it evenly across the broad point. Nibs divided into three 'tines' are commonly known as 'music' nibs, as their line, which can be varied from broad to fine, is suited for writing musical scores. Although the most common nibs end in a round point of various sizes (fine, medium, broad), various other nib shapes are available. Examples of this are oblique, reverse oblique, stub, italic and 360 degree nibs. Flexibility in fountain pen nibs is determined in several ways. First, thickness of the nib is important. When the nib alloy has been pressed thick it will result in a hard nib, while thinly pressed nibs are more flexible. Also, should a nib be thinner at the feed and thicker at the tip flexibility is improved. Second, the curve of a nib determines in part how stiff the nib will be. Nibs pressed into more deeply convex curves, or into three or five faceted curves will be stiffer than flatter nibs. Third, the "breather hole" size, shape, and position alter the stiffness. Should a heart shaped hole be wider than normal it will imbue a flexibility to the nib, while round, small holes give made a nib stiff. Fourth, the length of the tines determines how far they may spread under pressure. With shorter tines a nib will be stiffer. Fifth, the alloy used can affect stiffness, steel is stiffer than gold alloys, and more pure gold (18k, 21k) is softer than diluted gold.
Fountain pens dating from the first half of the 20th century are more likely to have flexible nibs, suited to the favored handwriting styles of the period (e.g.: Copperplate script and Spencerian Script). By the 1940s, writing preferences had shifted towards stiffer nibs that could withstand the greater pressure required for writing through copy paper to create duplicate documents. Furthermore, competition between the major pen brands such as Parker and Waterman, and the introduction of lifetime guarantees meant that flexible nibs could no longer be supported profitably. In countries where this rivalry was not present to the same degree, for example the UK and Germany, flexible nibs are more common. Nowadays, stiff nibs are the norm as people exchange between fountain pens and other writing modes. These more closely emulate the ballpoint pens modern users are experienced with, but are often described as feeling like "writing with a nail" by those who prefer the feel of a more flexible nib. (Nibs, especially more flexible nibs, can be easily damaged by ballpoint users who write with excessive pressure. Ideally, a fountain pen's nib glides across the paper using the ink as a lubricant, and requires no pressure.)
Good quality nibs that have been used appropriately are long lasting, often lasting longer than the lifetime of the original owner. Many vintage pens with decades-old nibs can still be used today.
Other styles of fountain pen nibs include Hooded Nibs (Examples of hooded nibs are Parker 51, Parker 61, or the current (2007) Parker 100, Hero 329), Inlaid Nibs (e.g., Sheaffer Targa or Sheaffer P.F.M) or Integral Nib (Parker T-1 and Falcon, Pilot Myu 701), which may also be ground to have different writing characteristics.
Users are often cautioned not to lend or borrow fountain pens as the nib "wears in" at an angle unique to each individual person. A different user is likely to find that a worn-in nib does not write satisfactorily in their hand and, furthermore, creates a second wear surface, ruining the nib for the original user. This, however, is not a point of concern in pens with modern, strong tipping material, as these pens take many years to develop any significant wear.
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