Steel nib demonstrator with a piston, carried nib up in a jacket pocket for a forty minute train, and about twice a week I uncap at the office to a cap full of ink and a wet nib. At my desk the same pen with the same ink is faultless all day. The carriage is warm and I usually have it about a third full by the end of the week. Is this a temperature thing, a seal thing, or a pen I should stop carrying?
The physics, roughly, because it makes the behaviour predictable rather than mysterious. A third-full converter or barrel is carrying something on the order of a millilitre of air, and air expands by about a third of a percent per degree Celsius. Go from a cold platform to a heated carriage, call it fifteen degrees, and you are pushing a few percent of a millilitre of volume somewhere. That is not much liquid in absolute terms and it is plenty to make a mess of a cap. Aeroplanes are worse because it is pressure as well as temperature.
Going to disagree with pure thermodynamics, because plenty of us carry half-empty pens on warm trains without a cap full of ink. Pull the nib and feed and check the nib is fully seated and that the feed channel is not crudded up, especially if you have cleaned it recently and pushed things back in by feel. A feed that sits a fraction proud does not buffer properly and you get exactly this: fine when static, wet when moved and warmed.
Also check the piston seal by holding it nib down under a bright light and watching for a bead forming at the nib slit over a minute or two.
Fair, and the two are not exclusive. A well-fitted feed tolerates a warm train with a half-empty barrel, a badly seated one does not. Worth checking the cheap thing first though, which is filling it fuller for a week.
I ruined two shirts learning this. Jeans pocket, nib down, one very hot afternoon. Now the everyday carry is a cheap cartridge pen in a hard slip case and the nice pens stay in a two-pen case in the bag, nib up. It is not glamorous but I have not lost a shirt in three years.
Carry it nib up. Keep it above half. If it still burps, the feed is not seated. Three things, in that order.
One more thing to look at: how much you are writing at the desk versus on the train. A pen that is used constantly is venting through the nib all day and never builds up any pressure differential. The same pen capped and jostled for forty minutes with no writing is a sealed vessel with a warm gas in it. If you doodle for ten seconds when you sit down, half the problem goes away, which is a strange but real fix.
@lowell_frame · 5mo ago · 3 replies
Two thirds air and a warm train is the whole story. The air in the barrel expands when it warms, it has nowhere to go except through the feed, and the feed fins can only buffer so much before it comes out the front and pools in the cap.
Things that fixed it for me, in order of how much they helped: keep the pen above half full and top it up mid week rather than running it down to fumes, carry it nib up so gravity is at least not helping, and let it sit nib up for a minute before you uncap after coming in from the cold or into a warm building. A pen that is nearly full barely burps at all, which is the opposite of what most people expect.
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@margin_notes_mo · 5mo ago
The nearly full point surprises everyone. It also means the last fifth of a fill is the worst-behaved part of the fill, which is when people conclude their pen has developed a fault.
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@notetaking_ivo · 5mo ago
Kept it above half all week and had one dry uncapping every day. Feeling slightly silly.
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