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Loss of ink volume in Jinhao models 777 and 993 (aka Shark) compared


A Smug Dill

I received dozens of cheap Jinhao pens at once, ten or so days ago, along with lots of 3.4mm-bore ink cartridges to fit them.

As they are either intended as future giveaways, or of an identical model to pens I've ordered (as gifts) sight unseen for delivery directly to the recipient, I wanted to get an idea of how they perform, not the least with regard to (what I've always described with the term) cap seal effectiveness. So, as a common "line in the sand", I plugged ink cartridges from the same tub into a couple of the pens.

For what does not appear to be a very wet-writing pen with an F nib, some 20% of the cartridge's ink volume was gone overnight, from the first Jinhao 993 pen I tested (note: not the one shown in the photo) having only written sparsely on a few A5 pages with it before bed. Alarmed, and in something close to disbelief, I decided to test a second Jinhao 993 (shown above) of the same colour and of the same lot with a new ink cartridge. Once ink has started flowing from the nib's tip, and I was satisfied that the nib writes OK out-of-the-box, I didn't write all that much with it, just a few lines every so often to check whether it's prone to hard-starting.

Yet, in spite of having a screw-cap, the second Jinhao 993 still manage to visibly lose significantly more ink volume in about four days than the Jinhao 777 with a snap-cap. I could see, through the translucent grip section and cap, that there was no pooling of ink in those parts; so it was definitely due to evaporation, and not just ink being drained into parts of the pen and remaining there in a liquid state.

I left the pens capped and mostly undisturbed for a few days, not so much a planned test tactic as simply having turned my attention elsewhere.

To my surprise, when I got around to checking them again, I could see the loss of ink from the Jinhao 993 appears to have been arrested, or at least greatly slowed. Could it be that the pen model's cap seal effectiveness is not as bad as I originally thought? All the same, the Jinhao 777 is obviously far superior in that regard.

While I was editing the comparison photo and annotating it, suddenly it hit me as to why the Jinhao 993 defied my expectations.

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The issue is that the interior of the Jinhao 993's pen cap has a large volume. Evaporation of solvents in the ink causes pressure to build up inside the closed cap, which increasingly suppresses further evaporation. With such a large interior space, it takes longer, and evaporation of more ink, for the process to come (close enough) to a halt.

But every time the pen is uncapped, the pressure is released, and so evaporation starts anew, and more ink volume is lost until the pressure inside the cap has built up sufficiently again after it has been screwed back on.

The same thing happens with the Jinhao 777 too, of course; but, given the much tighter fitting inner cap, it does not take long or much for evaporation to stop.

So, if both pens are uncapped (say) thrice every day, the Jinhao 993 is going to lose more ink to evaporation than the Jinhao 777. But if a filled Jinhao 993 was merely tossed into a drawer and left untouched for three weeks, it will probably still be ready to write, without having lost all that much ink from the pen's reservoir.

That goes against the conventional "wisdom" of writing with one's filled pens regularly and often, even if just to scribble a couple of lines, so as to keep the ink in the nib and feed liquid and prevent hard-starts. Uncapping a pen with a well-sealing cap more frequently, than is necessary for meaningful use, could actually promote evaporation of the ink, resulting in loss of volume and thickening of the ink, which causes ink flow problems and eventually dry-out.

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2ouvenir

Posted

@A Smug Dill May I ask how you add text to your pictures? Do you just do it in MS Paint? I find that when I try to add text with MS Paint, the resolution of the text turns out to be very low.

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A Smug Dill

Posted

7 hours ago, 2ouvenir said:

Do you just do it in MS Paint?

 

No. I haven't used a Windows PC in years, but I remember MS Paint. Ugh.

 

I alternately use GIMP (which will also run on a PC) and the standard Preview application on my Mac to annotate images, depending on what I'm doing. The text in the image here was added using GIMP, but the lines and arrows were drawn on it using Preview.

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2ouvenir

Posted

13 hours ago, A Smug Dill said:

 

No. I haven't used a Windows PC in years, but I remember MS Paint. Ugh.

 

I alternately use GIMP (which will also run on a PC) and the standard Preview application on my Mac to annotate images, depending on what I'm doing. The text in the image here was added using GIMP, but the lines and arrows were drawn on it using Preview.

 

Ah I see. I've never heard of GIMP, so thanks for telling me about it. Hopefully it isn't too difficult to use 😅

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