Friday, August 4, 2023

Plastic replacement cartridges for Eagle glass-cartridge pens


Eagle's glass-cartridge fountain pens are relics that I've always been content to regard as nonfunctional historic curiosities. A few years ago though after multiple requests for usable examples I adapted a few to use rubber sacs as simple squeeze-fillers. I only used pens missing their cartridge attachment nipples (originally soft rubber, they harden with age and sometimes crumble away entirely) which I replaced using hard rubber or plastic. A sac could just as well have been attached to an original hardened nipple, which would have been completely reversible. Nonetheless, I felt more comfortable installing sacs only on pens which already needed some degree of reconstruction, a few of which I already had around. Though the squeeze-filler conversion was less than elegant, implementing something closer to the original design was stymied by my inability to find a suitable modern replacement cartridge.

Completely by chance a small hoard of plastic storage vials came my way that turned out to be just the right size, requiring only to be shortened by 1/4 inch. Since their wall thickness is significantly less than that of the original glass cartridges, an original cartridge nipple is too small to fit.

The pen above was missing its original nipple so a new one of hard rubber was made to original dimensions. As an experiment, a retaining groove was cut so an O-ring could be installed to provide a seal. While the same could be done to an original nipple, leaving it intact would be far preferable. And, as I found out after further experimentation, far easier.

The section assembly above retains its original cartridge nipple. Rather than fit it for an O-ring, I cut a short ring from the end of a #14 ink sac and attached it with shellac. A smaller size sac was used so it would stretch to fit, its end wrapping around the end of the nipple slightly to create a rounded profile, allowing for easy insertion into the cartridge.

The photo above shows the same assembly with the cartridge mounted (though barely visible: I should have roughened or fogged the clear plastic to make it more visible). This adaptation is both cheap and fully reversible. If you try it, you will probably find that the rubber plug that the nipple is part of does not fit the section's metal outer shell tightly enough to prevent leakage. Since the material was originally soft rubber, when new it would have fit inside the metal shell like the cork in a bottle. Now that it has hardened, an ink-tight seal can be obtained using shellac or a product such as Captain Tolley's.

Please don't try mounting an original glass cartridge onto a nipple modified in this way. The glass is thin and sure to break. Instead, you could cut a slightly longer piece from a #16 sac, attaching it to the nipple with shellac and inserting the other end into the glass cartridge. A smear of silicone grease should keep the joint ink-tight. Make sure the sac is big enough; not all #16 sacs are identical, so it would be wise to pick one that is on the larger size.

The photo above should give you an idea of how this works, though I only had a damaged original cartridge handy (you can see the mouth isn't fully intact). The intact cartridge shown at the bottom of the photo below might have served, but it was stuck too firmly in place. 

NOTE: When cut to 2.75 inches long the new plastic cartridges fit Eagle barrels perfectly. So why are the original glass cartridges 1/4 inch shorter? The reduction in ink capacity is not a big deal, but that extra space at the end of the barrel could conceivably allow the cartridge to move far enough to come off the nipple. The answer is that these cartridges were designed to fit inside the barrel, filled and stoppered with a little cork plug, abutting the section nipple without being mounted upon it. 

The cartridge above has been emptied and cleaned, but the photo otherwise shows how these pens were originally sold, with a cartridge inside the barrel, sealed and uninstalled.

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