This is the 3rd of 4 inks that make up the Blackstone CMYK Ink kit - designed so you can mix your own custom colours. At the moment I'm just reviewing the 4 base colours (cyan, magenta, yellow and black)... Maybe later I'll mix some custom colours and post on the 'Inky Recipes' forum (?).
Yellow is the least usable of the base colour inks - for obvious reasons. I'd call this a 'pure' yellow, as compared with the stronger, slightly orange yellows I've compared it to (Blakcstone Golden Wattle and Diamine Sunshine Yellow). I'm sure it'll mix in a treat with the other colours - just don't expect to get much use of this ink on its own, unless you're wanting to cause eye strain! [To be fair, it dries a little darker than it appears while writing - though this means it's harder to see what you're writing than to read what you've written, which causes some hassles of its own...]
These are not my first mixable inks - I bought the whole Toucan range when Kevin from Just Write Pens (and now also Blackstone Inks) first started spruiking them. The Toucan inks are highly mixable, but aren't the most lubricated of inks - they tend to need a fairly wet pen to get reasonable flow and saturation. These inks, by contrast, have excellent 'inky' qualities, and play very nicely with my 'regular' pens.
By way of disclaimer, I purchased the CMYK mixing kit with my own funds, but have received complimentary ink samples (and prototype pens) from the manufacturer in the past. I have not received any financial compensation for putting up this review - it's entirely my own initiative.
For more comments , see my first review of the range (http://www.fountainp...cmyk-inks-cyan/). You can check out the manufacturer's summary at http://www.blackstone.ink/index.php/blackstone-cmyk-ink-mixing-set.
A scan and a photo (please forgive the inconsistent lighting for the latter):