A couple of years ago, I wrote an article for Interesting Thing of the Day about Fisher Space Pens, those wonders of modern technology that can write upside-down, in zero gravity, in a vacuum, or underwater. I mentioned my happy discovery that Space Pen refills were available in purple, my favorite color. A few months later, Fisher sent me a prototype of a new pen model for testing, including a purple refill. And I was cautiously optimistic that I’d discovered the ultimate pen for my needs.
I was reminded of all this when writing my article about Non-Newtonian Fluids, because the thixotropic ink in Space Pens happens to be such a fluid. And I thought it was high time I posted a follow-up about my purple-ink Space Pen experience, because it turned out to be an unhappy one.
Whatever else you can say about Space Pens, I discovered that those with purple ink have one huge and unforgivable flaw: the ink isn’t waterproof. Sure, you can write on greasy paper in a snowstorm, but if you later try to read what you wrote, you might have problems.
To illustrate, I took an index card and wrote on it in both black and purple Space Pen ink, and then dunked it in room-temperature water for 30 seconds. Only the lower half of the writing was submerged, and I think you can see pretty clearly what happened (click the photos for larger versions):
The black ink bled a bit, but the purple bled a lot. I actually discovered this when a piece of paper in my pocket, inscribed with the purple ink, got a bit damp from sweat. And it turns out that it’s just as bad as I feared.
But wait: aren’t you supposed to be able to write underwater with these pens? I tried that too, and the results were interesting:
As you can see, the purple again runs much more than the black. A half hour later, the purple ink had faded to a very light, almost illegible hue, while the black (though very slightly runny) was still nice and dark.
So now, if I want the Space Pen benefits, I have to choose which trade-off I prefer: ink color or smeariness. Ack. I don’t know whether the same problem affects the other colors of Space Pen ink (there are quite a few), but I do know that in at least this respect, the pens don’t live up to their advertising.
On a cheerier and somewhat related note, have a look at 8 YouTube Videos Featuring Non-Newtonian Fluid Experiments at SenseList, none of which involves Space Pens.
