Why do pens burst when they're sitting in your pant or shirt pocket?

November 24, 2006 1:10 AM

Why do pens almost always burst forth their precious ink when they get put in your shirt pocket or pant pockets?
posted by Effigy2000 to grab bag (20 comments total)

Cos they're warm?
posted by pompomtom at 1:47 AM on November 24, 2006

Murphy's law.
posted by IronLizard at 2:26 AM on November 24, 2006

You know how with some pens, if you start writing on a piece of paper but then leave the tip in the same spot, the paper will keep absorbing ink? Like markers, only not nearly as severe?

Fabrics are generally more absorbent than paper, so prolonged contact between exposed tip and fabric = more ink spillage.

I made this theory up just now, but it sounds viable to me.
posted by chrominance at 2:44 AM on November 24, 2006

Chrominance is correct for those cases where the ball of the pen is in contact with the fabric.

The other reason is what pompomtom says: they get warm, and just like a thermometer, the ink runs up and out. It's worse in the wash. The old Bic pens were especially bad this way.
posted by Goofyy at 3:13 AM on November 24, 2006

I think pants pocket ink leaks might also have to do with increased stress on the pen if the pocket is too tight. This might encourage seepage in a normally non-leaky pen.

Anectdotal evidance that might point to the correctness of chrominance's theory: I left an uncapped ballpoint pen in my jacket pocket. I took a nap on the pen in my truck for a couple of hours. It soaked through the pocket and into the seat fabric.

I think I know what my next askme question is going to be.
posted by Mister Cheese at 3:22 AM on November 24, 2006

It might also happen if you change altitude. I've had pens that peed all over my pocket in airplanes. Some pens are made with pressurized cartridges, so they will write upside down, and but many, like the Parker pen I remember decorating my shirt, aren't. I don't know whether pressurization of cartridges is a predictor of unleakiness. My guess is that price probably is. FWIW, that Parker T-ball was the last pen to misbehave like that, and that was about six years ago. (Also, it was not a fabric-contact leak; the whole barrel of the pen was slimed inside.) I carry a pen every day.
posted by Kirth Gerson at 3:46 AM on November 24, 2006

I've kept them in pen holders (without lids) and they have leaked out and inked up other pens, and everything goes green and icky. I think it might be the combination of being upright, without a lid on.
posted by b33j at 4:24 AM on November 24, 2006

The material acts as a wick, like in an oil lamp. Body warmth probably facilitates the process.
posted by furtive at 5:28 AM on November 24, 2006

I've carried pens in my pockets for more than twenty years and never had this happen...
posted by jdroth at 5:41 AM on November 24, 2006

Ditto, jdroth. I think it's because I put the cap on the pen before pocketing it. Why on earth are people walking around with uncapped pens in their pockets? Asking for trouble.
posted by jack_mo at 5:51 AM on November 24, 2006

Quite apart from anything else, that uncapped pen in your pocket probably won't be any use for writing anyway, since the nib will have dried out. Always cap your pens, people.
posted by reklaw at 7:11 AM on November 24, 2006

Confirmation bias?
posted by sourwookie at 7:50 AM on November 24, 2006

Not all pens have caps. Parker T-ball jotters, for instance, and the Cross pens I've seen. That's why there "are people walking around with uncapped pens in their pockets."
posted by Kirth Gerson at 8:30 AM on November 24, 2006

The concept a number of people are referring to is capillary action.
posted by kimota at 8:58 AM on November 24, 2006

Osmosis. What furtive said.
posted by rokusan at 9:50 AM on November 24, 2006

I think confirmation bias, because (like people above) I carry a pen in my pants pocket almost always (for the last 5-6 years), and I've had a pen burst in my pocket exactly once ever. And that one time I'm pretty sure was in an airplane, as a result of a pressure change.
posted by advil at 12:40 PM on November 24, 2006

It's a trait retained from octopuses: when confined and frightened, they squirt. Sometimes they will also jab your thigh.
posted by Clyde Mnestra at 1:32 PM on November 24, 2006 [2 favorites]

I've only had pens do this when they've been used a while.
posted by metaswell at 10:19 PM on November 24, 2006

I've only had pens do this when they've been used a while.

Theory: Roller ball wear and deformation of the housing allow ink to pass freely, particularly when viscosity thinned by heat.

To test theory: Put an assortment of pens sorted by age in your pocket, point down on a hot day. Report back.
posted by IronLizard at 10:25 PM on November 24, 2006

I'm going with capillary action, or pressure change depending on the type of pen.

My experimental results. (of a sort)

Retractable pen in a bag. for 3 months, no problems. Then one day I notice a lot of ink in the bag. The pen was stowed without retracting it. I cleaned the bag, and since then have made sure the (Very same) pen has been retracted when I stow it.

To confirm the results, I should once again place it in the bag extended. However the completion of the experiment is pending funding to replace my 'spensive bag and/or pen.

I believe that movement probably also exacerbates problem, putting more fibers in contact with the ink and spreading it further.
posted by Ookseer at 12:43 AM on November 25, 2006