Archive for September 6th, 2015

HP 7475A Plotter: Zombie Pens

Following madbodger’s recommendation, but finding no local sources, a bottle of Koh-I-Noor Rapido-EZE Pen Cleaner solvent arrived. It’s billed as a solvent & cleaner for drafting ink, not plotter ink, which seems like an unnatural restriction.

I’d previously tried refilling some fossilized pens, only to find that the ink simply won’t flow through a nib filled with dried ink. So the pens you’ll see here have refilled reservoirs atop nibs that don’t write.

Dismantling the Koh-I-Noor black pen produced this unsightly mess:

HP 7475A - Koh-i-Noor black pen parts

HP 7475A – Koh-i-Noor black pen parts

I pushed the nib out of the shell using a pin punch, pretty thoroughly crushing the tip in the process. The ink reservoir looks like some sort of fluff inside a plastic sleeve, with a hole left by the butt end of the nib and a crust left by the evaporating ink. I scraped off the crust, put the nib in a cylinder filled with solvent, and let it sit for a few days, after which most of the black ink had vanished.

I reassembled the pen with the blunted end of the nib inside the body and the reservoir flipped end-for-end, in the hope that would work better.

Trying a different tactic with a Staedtler green pen, I removed the reservoir, filled the body with solvent, and dunked the tip in a solvent bath:

HP 7475A - Staedtler pen - nib soaking

HP 7475A – Staedtler pen – nib soaking

After a few days, the body was still mostly full of solvent, so it’s not flowing freely through the nib. Perhaps leaving the nib in air would encourage the fluid to move outward, at the risk of drying the nib even more.

Refilling them with inkjet printer ink produced this:

HP 7475A - Koh-I-Noor 2 - Staedtler 3 - zombie pens

HP 7475A – Koh-I-Noor 2 – Staedtler 3 – zombie pens

Pen 2, the gray K-I-N trace, seems a bit pallid, likely due to using cheap black inkjet ink. Apart from that, it’s continuous and presentable.

Pen 3, the green Staedtler, remains in the land of the undead; its ink flows better than before, but not enough to be worthwhile. The demo routine writes the annotation first and those characters came out well enouigh.

The other two pens also carry refilled ink: Pen 1 = ceramic tip, Pen 4 = Staedtler fiber (which, judging from the cap color, started out as gray and has become much darker after the inkjet ink refill).

All in all, a modest success and I’ll try again later. Better, however, to refill each pen before it dries out, as with the two “good” pens.

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