Although other kinds of pen have also been called "safeties" – usually, early screw-cap models with inner caps – to most collectors, a safety pen is a fountain pen with a nib that can be retracted into the barrel, permitting the cap's inner surface to seal the ink chamber like a cork plugging a bottle. In the United States, Waterman was the main maker of safety pens, though by no means the first. A Waterman 442 1/2 Filigree appears above; as with most safety pens, the end knob is turned to extend and retract the nib by means of an internal screw mechanism. For more on Waterman safeties, look here.
A notable and long-lived exception to this basic design was the Moore, which used a simple push-pull action. A Moore Non-Leakable cutaway appears above; you can read more about Moore safeties here.
Although safety pens were first made in America – the Horton, shown above, was put into production in 1894 – their popularity was greatest and most lasting in Europe, most notably in France, Germany, and Italy.
While the market for safety pens in Germany was dominated by German penmakers, Waterman was the market leader elsewhere in Europe. Nor did Waterman settle for a one-size-fits-all approach, instead offering a broad range of country-specific models and overlay patterns. Local pen makers also produced safeties, but they tended to be followers rather than leaders.
The richest range of overlays was to be found in Italy; an example from the 1920s with relief decoration that combines Art Nouveau foliage with a classicizing mask appears above. The Italian-overlaid Watermans are sometimes misleadingly termed "Continental" safeties. In fact, they are distinctly Italian; no other European country so embraced elaborately-worked overlays. France, for example, favored pens in mottled or woodgrain hard rubber, preferring simpler overlays with regular engine turned patterning. The pen below exemplifies French taste in safety pens, and is typical in carrying a rather small, 18K gold nib.
Virtually all safety pens were made of hard rubber. An unusual exception in black and pearl celluloid is shown below. Some later German and French safeties were made in demonstrator form, with transparent barrels. These are not commonly seen.
Safety pens are still practical writing instruments, but it is necessary to replace their seals before they are put into use. Note that most repairmen outside Italy and Germany are not experienced in safety seal replacement, so beware of sellers who offer "working" pens whose ancient seals are likely to fail within days if they are placed in regular service. A properly restored safety lives up to its name, in that it holds its ink more securely than any other pen. Normal pens will eventually dry out if left unused for a matter of weeks, even if capped, but ink evaporation in a safety is so minimal that it would take years before drying out. And since a safety's nib remains immersed in ink when not in use, safeties can be used with thick inks that would gum up just about any other fountain pen -- even India ink (though we offer no guarantee if you choose to experiment!). For this reason, around 1940 Waterman offered specialized safety pens targeted specifically at artists and musicians. Another was marketed for aviation, since safeties are largely unaffected by changes in atmospheric pressure between uses (each time they are uncapped, outside and inside air pressure is equalized).
To fill a safety pen, the nib must be retracted, and ink put into the barrel using an eyedropper. The barrel must always be held upright whenever the pen is uncapped and the nib retracted, otherwise the ink will pour out the open barrel end.
FAQ article: Practical advantages of safety pens
Pen Profiles: Waterman safeties, Moore safeties
Original 1920s Waterman eyedropper instruction sheet