That cloudy shape is the mold, or some sort of organic growth. Among fountain pen people, it’s often called SITB — slime in the bottle.
You can see it’s organic matter: the shape changes when the cartridge is turned over and the mold moves around.
Here it is moments later.
Every single one of the eight cartridges has this inside, although in the photo below it’s easier to see in cartridges three through five.
So, unfortunately, I won’t be sending these Golden Yellow cartridges to friends, or using them myself.
I bought the cartridges about two weeks ago at the Chicago Pen Show. This isn’t a stale batch of inks. The expiration date is May 2018. All cartridges are unused and sealed.
Luckily I noticed this before putting in in an expensive pen.
But the most annoying thing? Montblanc USA won’t do anything for me. The phone representative was extremely nice, polite and well-trained, and he seemed grateful I called — he said he’d notify the warehouse to check their new stocks of Golden Yellow. However, Montblanc USA policy apparently requires me to return the item (at my expense) to the place of purchase. He didn’t even take my name.
Candidly, having bought a lot of Montblanc products before, and always having been happy with their service before, I expected better. Especially in a situation with a clear manufacturing issue.