Wax on pens

I'm not sure how it all started, but in the past ten years or so it seems a significant number of enthusiasts have begun waxing their pens. While this may make some sense for pens with finishes that cannot take much polishing, or which are especially vulnerable to environmental exposure, there are many cases where wax is decidedly not a good idea.

Heading the list are pens made of celluloid or cellulose acetate. Both materials give off acid gases as they age, gases which can accelerate the aging process if not allowed to escape (more on celluloid storage here). Coating a celluloid or cellulose acetate pen in wax will prevent escape of those acids, trapping them within the material. The harder waxes favored for use on pens, such as carnauba, are also the least permeable, despite recent claims of breathability on pen forums (see Greener Donhowe, O. Fennema, "Water vapor and oxygen permeability of wax films", Journal of the American Oil Chemists’ Society, Sept 1993, vol. 70, issue 9, pp. 867-873).

Wax on hard rubber is a more mixed case. Protection from light and in particular UV will be minimal, so the main benefit would be to exclude moisture. Water will have no effect on pristine hard rubber, but exposure to light will eventually break down the crosslinks formed during vulcanization. This surface damage is often invisible until the rubber is exposed to water, at which point it will fade instantaneously as de-crosslinked material is washed away. Humid air can have a similar effect, though without the loose surface compounds being washed away. Instead, one ends up with an acidic crust, thanks to the free sulfur in the damaged surface. Waxing hard rubber that has latent surface damage (that is, exposure to light, but no exposure to water) would help prevent both fading and formation and release of acids.

Wax does change the look and feel of a surface, however, and waxes do inevitably break down, losing their ability to protect and turning cloudy or yellow. If the dulled wax is difficult to remove, this can be a serious problem. What seems wonderful for the first few years can become a nightmare after ten or twenty. For while polishing off old wax residue may be no big deal on a wooden table or a steel knife blade, it's quite another matter to get it off something like the delicate and irregular surface of Japanese maki-e lacquer work.

As important as knowing when and when not to wax, is knowing what wax to use. For a knockabout pen of no historic value it doesn't really matter. For something rare and significant, though, you'll want to approach wax selection like a conservator. Commercial products for household or automotive use would be disqualified immediately. You'll want to avoid waxes such as beeswax and carnauba, which are either acidic or prone to become acidic as they age. You'll also want to avoid polyethylene waxes, which under some circumstances can be almost impossible to remove (see Danal L. Moffett, "Wax coatings on ethnographic metal objects: justifications for allowing a tradition to wane", Journal of the American Institute of Conservation, vol. 35, no. 1, 1996, pp. 1-7, where removal required nothing less than immersion in hot xylene). A pure microcrystalline wax such as Cosmolloid 80H would be the conservator's choice, according to the current literature. I would advise against Renaissance Wax, which is a mixture of microcrystalline and polyethylene waxes. It is widely advertised as a museum-grade product, but what was museum-grade back in the 1950s when it was developed is very different from what is museum-grade today.

ADDENDUM: In this thread at FPN, users of Renaissance Wax report it discoloring hard rubber upon application. These would appear to be instances of solvents in the wax reacting with a surface layer already degraded by exposure to light, akin to how such surfaces can instantly fade when exposed to water.