I haven't reviewed many Private Reserve inks so far, and Invincible Aqua Blue makes my third. It's also the most "exotic" of them, mostly because it has been discontinued (correct me if I'm wrong). This means that you won't be able to buy it anywhere, which makes this review almost pointless. However, since I managed to grab a sample before it disappeared completely, and because I tested it anyway, I thought it might be worth posting a review just for completeness' sake.
The other thing that makes Private Reserve Invincible Aqua Blue special is its water resistance, denoted by the term "invincible" in its name. I rather like this. I wish other brands followed a similar naming scheme. Noodler's Ink comes close with certain ink series (Hunter, Bad..., Baystate, etc) but it's still erratic.
But enough chit-chat. Let's get down to reviewing this now-defunct ink, which I tested in my Pilot Varsity.
Back when you could still buy it, Private Reserve Invincible Aqua Blue retailed for... hmm... I don't know anymore, because I failed to record the price. However, going by the price of its surviving sibling, Invincible Black, you will notice that it costs about $9.75 for a 2 oz (60 ml) bottle, or $0.16 per milliliter. That's not very expensive at all for a waterproof ink.
Color and saturation
Invincible Aqua Blue is an aqua-bluish kind of ink. That means it is a lightly saturated light blue color. It reminds me in a way of Noodler's Polar Blue, which also happens to be a waterproof ink, with the special distinction that it is also cold-resistant. Although the two inks are distinctly different (with Polar Blue darker and more saturated), they both have the "faded jeans" look.
Invincible Aqua Blue is quite flat and doesn't show any shading.
Unfortunately this ink tends to penetrate the paper a little. It doesn't bleed heavily but it ghosts a little on cheap paper and almost shows through where the nib presses harder. In this case it's a good thing the ink is only lightly saturated.
Flow and lubrication
Invincible Aqua Blue flowed well in the Pilot Varsity, perhaps a bit on the wet side.
One good feature of this ink is that it dried extremely quickly. As you can see from the two samples, it dried in less than 5 seconds even on the shiny Rhodia 80g paper.
Smearing when dry
Private Reserve Invincible Aqua Blue was marketed as a waterproof ink and, true to its purpose, it casually rejected any attempts to wash it off with water. I didn't try other liquids.
I have no idea why Private Reserve decided to discontinue Invincible Aqua Blue. It's not a bad ink by any means. The only negative is that it bleeds a little on cheaper paper but that shouldn't be a major detractor. I'm sure they had their reasons for it and I'm not going to waste time googling it. Too bad it is not among us anymore but what can we do about it? If you are looking for a waterproof ink with these qualities, the closest I can recommend is Noodler's Polar Blue. You can even dilute it a little with water if you want to match colors.
Following are the two samples written on photocopy and Rhodia 80g paper, respectively.