By Ben L.
Anyone who’s purchased a TWSBI Eco has seen the little tag that comes under the clip warning you not to use alcohol based cleaners. But in these dire times when sanitation is paramount, are you putting your pens at risk by potentially exposing them to hand sanitizer?
The reason TWSBI Ecos have that warning tag is because they’re made of polymethyl methacrylate, which is marketed under brand names like Plexiglass and Perspex, and more widely known as acrylic. This is unique among TWSBI’s offerings, as their other models are made of polycarbonate resin that’s more resistant to solvents. However, acrylic is present in other pens, especially those with bodies made from resin blanks turned on a lathe, as the blanks frequently have acrylic as their primary ingredient.
Acrylic is reactive with a handful of polar solvents such as alcohols, and as a result could potentially be damaged by exposure. Conveniently for us, because knowing the resistance of different plastics to solvents is extremely important for knowing when they’re suitable for industrial applications, companies who sell them publish the results of comprehensive testing of their resistance to different solvents. The analysis I looked at assessed the behavior of acrylic with an extremely wide range of solvents and substances potentially encountered in industrial applications such as jet fuel and ozone. Reactivity was ranked on a four tier scale, from E: “30 days of constant exposure with no damage. Plastic may even tolerate chemical for years.” to N: “Not recommended for continuous use. Immediate damage may occur such as severe crazing, cracking, or permeation losses.”
The vast majority of hand sanitizers are alcohol based, with the active ingredients usually being some combination of isopropyl alcohol and ethanol at a concentration of 60 to 95%. At room temperature, isopropyl alcohol’s reactivity with acrylic was rated as the 2nd highest level, F, meaning that there was “Some effect after 7 days of constant exposure to the reagent. Solvents may cause softening, and swelling.”, and ethanol received the same rating.
What does this mean for you when you’re using hand sanitizer around your pens? Practically nothing. The samples tested by the lab were continuously exposed to a high concentration of each alcohol for several days, and unless you’re using so much hand sanitizer it’s dripping on the page as you write, the time your pens will spend in contact with the solvents is on the order of seconds each time you sanitize your hands before picking them up. Effects of excessive exposure to reactive solvents include discoloration, swelling, puffiness, softening, or cracking, so it’s still wise to avoid excessive contact between the acrylic of an Eco and any harmful solvents, but the impact of getting a reasonable amount of hand sanitizer on a pen isn’t big enough to worry about.