What causes ink to find its way inside the cap?

[Blade Runner]

In the absence of an obvious leak or jostling, i find some ink inside the cap of a couple of my pens. I notice this when i've carried them in my shirt pocket.

Body heat and condensation? Anyone else run into this?

 

Thanks,

 

Jeen

[KCat]

often. but never gave much thought to why it happens. Depends on the pen though. A slip cap like a Parker or Hero seems to be more prone to this. i always figured in *that* case it was due to the suction and pressure of pulling off the cap and putting it back on. Especially if you use the two-handed method of uncapping. one-handed should reduce this.

 

but i see it on screw-caps as well so i'd go with the jostling theory for the most part.

 

if it were just condensation, the liquid should be clear as the dye would be left behind. at least, if i'm remembering basic chemistry properly. I'm no dye expert so maybe there's something I don't know about it that would change my conclusion.

[southpaw]

if it were just condensation, the liquid should be clear as the dye would be left behind. at least, if i'm remembering basic chemistry properly. I'm no dye expert so maybe there's something I don't know about it that would change my conclusion.

Ink evaporating would leave the pigments / dyes behind - just the water and any VOC's would evaporate (VOC = volatile organic compounds).

 

I think y'all are right on target as to the source of ink in the cap. Most likely jarring, but also thermal expansion from body heat if it has a sac - one of the main reasons I got rid of nearly all of mine - I'm just too hot I guess (hold your fire - meant that in body temp only!!!!!).

[Blade Runner]

Thanks Kcat and Southpaw,

 

I think the prob is often due to condensation, esp with big pens with conical caps like the 149 on hot days. But i was very interested to hear Kcat about your statement about ink getting pulled out by the suction effect of removing the cap. I have a modern pen with a twist off cap that sometimes has a small amount of ink on the nib upon removing the cap, and i think this suction effect is at least part of the reason. Strangely, it hasn't happened lately, and there be other factors such as the amount of ink in the chamber or how much air got pulled into the chamber upon filling. The last time i filled i made sure the section was immersed precluding air entering the chamber, and no ink appears on the nib upon removing the cap.

 

Regards,

Jeen

[antoniosz]

Southpaw's observation is correct. It can not be evaporation/condensation (which is observed too but the dropless are clear).

It comes from small sudden movements that tend to "eject" the ink into the cap.

Having it in your shirt's pocket makes it succeptible to such motions from waling, running, driving over a pot hole etc. Kcat point is also possible re snap caps, but it is often observed in screw caps (like Pelikans). Example my Kaweco sports that I carry in my pocket. Wet writers are more prone - hot weather might also be a factor.

 

Remember that ink stays in the feed/nib under the action of underpressure in the ink chamber, capillary in the nib/feed, atmospheric pressure and gravity - in other words very small forces. Sudden motions cause the ink to be ejected by inertia.