I was cleaning out my desk at home over the weekend and found two bottles of Waterman Intense Black ink. As far as I can tell they have never been opened, and they have been stored at moderate temperatures away from light. I probably bought them after I got my Parker UK Duofold, which would have been no more than nine years ago--probably more like seven or eight years. There's no date on the bottles or boxes. Would they still be safe to use? If I decide to try this ink, are there any warning signs I should watch for?