Ask The Desk: Condensation in my TWSBI

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Chris asks:

My wife bought me my first TWSBI for Christmas this year–a TWSBI Mini demonstrator. I’ve filled it with Iroshizuku Kon-Peki and carry it in my front shirt pocket, right next to my heart.

One problem: I’ve had trouble with moisture collecting inside the cap and the grip section of the pen. Initially the cap was the only culprit. Now, the condensation is found in both locations. The cap is easy enough to clear with a cue-tip, but the grip is a little more difficult.

Have you had problems with moisture so collecting in any of your TWSBIs or is there something I could do to prevent it?

I suspect the moisture is a result of condensation from the temperature changes. Especially if you are keeping your pen close to your body, it may warm up. Then when it cools on your desk or faces the arctic outdoor temperature shifts, there may be some moisture that builds up in the cap. I suspect that other fountain pens may face the same issue but without the clear cap and grip, we don’t ever notice it.

A quick search on the internet for “demonstrator fountain pen condensation” revealed that this is not an issue exclusive to the TWSBIs. It appears that most demonstrator pens will reveal some sort of condensation or ink in the cap over time.

disassembled TWSBI mini

My Mini tends to get it less frequently in the grip area unless I’ve recently cleaned it. If I don’t let it dry completely before reassembly, I get moisture in the grip section as well. With a firm push on the threaded end of the nib unit, it should pop out of the grip area allowing you to easily swab out any condensation build-up. Then reassemble it.

I have some of those long cotton swabs on a wooden stick that let me wipe away any moisture or stray ink from the inside of the cap though a standard issue Q-Tip should reach just fine.

Does anyone have advice for minimizing the condensation build-up?

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  1. I’ve had the exact same issue with my 580. Everytime it spends more than 10 minutes in my shirt pocket I get condensation in those two places. Unfortunately the only solutions I’ve discovered are obvious: don’t carry it in that pocket or don’t worry about it because this won’t cause enough condensation to hurt the pen. No matter how much of a human oven you are.

  2. Keep the pen full. Try a different ink? I don’t see this condensation with my demonstrator pens. But I live in a country on the equator, so temperature changes from pocket to ambient and vice-versa are not extreme.

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